Midwest Blueberry Production Guide

COOPERATIVE EXTENSION SERVICE UNIVERSITY OF KENTUCKY COLLEGE OF AGRICULTURE, FOOD AND ENVIRONMENT, LEXINGTON, KY, 40546

ID-210 Midwest Blueberry Production Guide

Agriculture and Natural Resources • Family and Consumer Sciences • 4-H Youth Development • Community and Economic Development EXTENSION

Contents

1 Introduction...... 3 2 Blueberry Growth and Development...... 4 3 Types of Blueberries and Cultivar Selection...... 7 4 Site Selection...... 12 5 Planting and Establishment...... 14 6 Irrigation and Water Management...... 16 7 Pollination...... 19 8 Propagation...... 20 9 Pruning and Growth Management...... 22 10 Soils, Fertilization, and Nutritional Disorders...... 25 11 Blueberry Diseases...... 29 12 Insect and Mite Pest Management...... 39 13 Managing Wildlife Problems in Blueberries...... 49 14 Weed Management...... 52

Edited by Nicole Ward Gauthier and Cheryl Kaiser, Department of Plant Pathology, Uni- versity of Kentucky

Contributors University of Kentucky—Tom Barnes, Department of Forestry; Chris Smigell, John Strang, Dwight Wolfe, and Shawn Wright, Department of Horticulture; Nicole Ward Gauthier, Department of Plant Pathology University of Missouri—Patrick Byers, Extension Service Pennsylvania State University—Kathy Demchak, Department of Horticulture The Ohio State University—Michael Ellis, Department of Plant Pathology; Gary Gao, South Centers and Department of Extension Michigan State University—Eric Hanson, Department of Horticulture; Rufus Isaacs, Department of Entomology University of Arkansas—Donn Johnson, Department of Entomology Mississippi State University—Eric Stafne, Department of Plant and Soil Sci- ences

The Midwest Fruit Workers would also like to thank the authors of the following publications for contributions to this guide: Mid-Atlantic Berry Guide, Michigan State University Blueberry Facts, and Northwest Berry and Grape Information Network.

Cover photo: Mark Ehlenfeldt, USDA-ARS

Mention or display of a trademark, proprietary product, or firm in text or figures does not constitute an endorsement and does not imply approval to the exclusion of other suitable products or firms.

Chapter 1 Introduction

lueberries are one of the few fruit Bcrops native to North America. Wild blueberries were utilized by Na- tive Americans for making medicines, dyes, and flavorings, as well as for direct consumption. Once a small-scale crop produced within limited regions, blueberries are now grown throughout the United States and the rest of the world. Although highbush blueberries (Vac- cinium corymbosum) are the primary type of blueberry grown commercially, others such as southern highbush (Vac- cinium spp.), rabbiteye (V. virgatum; syn. V. ashei), and lowbush (V. angustifolium) are commonly grown in regions that suit their horticultural requirements. Before improved varieties were available for commercial production, wild blueberries were used to supply the imports fruit from other countries, such of “bad” cholesterol and slowing of age- market demand. Highbush blueberry cul- as Canada and Chile, between harvest related memory loss. Increased recogni- tivation and breeding programs, which seasons. tion of these and other health benefits began in the early 1900s, paved the way Commercial production of blueber- contributed to the 160 percent increase for the modern blueberry industry. Early ries is a relatively new phenomenon when in U.S. blueberry consumption between blueberry production was limited to the compared to other fruit crops (such as 1994 and 2003 and has also sparked an eastern United States and Upper Mid- apples, peaches, and grapes). Cultivated increased use of blueberries in jams, jel- west, but with the new cultivars available, blueberry acreage, which was essentially lies, and pastries. growers and researchers alike began to nonexistent during the last century, is Additional Resources look outside of this region. By the 1930s more than 70,000 acres in the United and 1940s, blueberries were being grown States alone. Markets are varied, with Bushway, L. 2005. Eat your blueberries. in North Carolina and the West Coast, berries sold in both retail and wholesale Cornell University. http://www.fruit. with further expansion occurring in markets. Small scale, local production cornell.edu/berry/. subsequent decades. Desirable traits were has also grown substantially in recent Coville, F.V. 1937. Improving the wild intensified, and the highbush blueberry years, including farmers markets, road- blueberry, pp. 559-574 in United States industry continued to grow worldwide. side stands, and pick-your-own. Department of Agriculture Yearbook Today, nearly 90 percent of the world’s Blueberries, when compared to other of Agriculture 1937. Washington, D.C. blueberries are grown in North America. fruits, are desirable because they have Eck, P., R.E. Gough, I.V. Hall, and J.M. Spi- The main blueberry production small seeds, thin skins, vibrant flavor, ers. 1990. Blueberry management, pp. regions in the United States are the attractive color, good storage capabil- 273-333 in Small Fruit Crop Manage- Northeast (Maine, New Jersey, New ity, can be mechanically harvested, and ment. G. Galletta and D. Himelrick, York), Southeast (Alabama, Florida, are adaptable for value-added products. eds. Prentice Hall, Englewood Cliffs, Georgia, Mississippi, North Carolina), In addition to flavor, blueberries have a NJ. Northwest and West (California, Oregon, number of health benefits, such as low Economic Research Service. 2012. Washington), and Midwest (Arkansas, levels of calories, sodium, and choles- USDA http://usda.mannlib.cornell. Indiana, Michigan). The production-use terol, along with high vitamin C and edu/MannUsda/viewDocumentInfo. in the United States is divided between fiber. Blueberries also contain one of the do?documentID = 1765. fresh and processed, with a slight ma- highest levels of antioxidants, including Pritts, M. and J. Hancock. 1992. Highbush jority (about 55 percent) sold for fresh flavonoids and phenolic compounds, of blueberry production guide. Northeast consumption. The United States not any other fruit or vegetable. Researchers Regional Agricultural Engineering only exports blueberries, but it also have linked blueberries to the reduction Service, NRAES-55.

3 Chapter 2 Blueberry Growth and Development

lueberry plants (Figure 2-1) are peren- Bnial woody shrubs that mature in 5 to 7 years. Canes emerge from a central crown, and each plant typically produces 15 to 18 upright canes by maturity. Growth habit is usually upright, although some cultivars have a spreading form. Blueberry plants are deciduous, reaching full dormancy during the winter months. Most highbush blueberry cultivars re- ° quire over 600 hours below 45 F to satisfy Figure 2-1. Blueberry bush with ripe berries. their chilling requirement. Plants break dormancy in spring after chilling requirements are met and tem- Once chilling hours are met, warm well as throughout the year, as necessary. peratures begin to warm. Often, chilling temperatures can coax blueberry plants Hot weather above 95° to 100°F can lead period requirements are reached during out of dormancy, leading to greater freeze to high water loss, so supplemental water mid-winter, and then cold temperatures sensitivity. Fluctuations between above- availability is critical in order to avoid maintain dormancy. Warm spring tem- freezing and below-freezing tempera- plant stress. peratures break dormancy, but once tures result in loss of hardiness, especially Flowers dormancy is broken, sap begins flowing, during the spring months. Typically, the making plants more susceptible to freeze more southern latitudes in the U.S. have Blueberry flower buds form in au- damage. As flower buds begin to swell, greater temperature fluctuations in tumn, with 5 to 8 flower buds on each leaf emergence and shoot growth occurs. spring. While upper plant parts acclimate shoot (highbush). Each bud has 5 to 10 This shoot growth continues through to winter temperatures, roots do not ac- potential flowers. Flowering can last 1 to 2 flowering. The first growth flush is the climate because they are protected from weeks, although early flowering cultivars most vigorous, but at least two additional, extreme temperatures by soil. In areas usually bloom for a longer period due in less vigorous growth flushes occur later where extreme cold temperatures are part to genetics and to cooler tempera- during the season. Emerging young, ten- prevalent during winter, mulch serves tures. Buds on shoot tips open first, and der green shoots eventually mature to as an effective insulator (see Chapter 6: then flowering occurs sequentially down produce woody canes. Irrigation and Water Management). shoots. Buds on thin canes open before As day length shortens and tempera- Cold tolerance and acclimation those on thick, woody canes. tures cool in autumn, growth ceases and (hardening-off) are also dependent upon Blueberries have urn-shaped, inverted plants begin to acclimate for dormancy. plant health and vigor. Stressed blueberry flowers (Figure 2-2) that shield them from This acclimation is a major contributor to plants often do not properly acclimate or wind and rain. As a result, self-pollination cold tolerance. Until hardened off, plants reach maximum cold tolerance levels. often cannot occur and pollination by can be damaged at temperatures as low Plants build up food reserves during insects is required (see Chapter 7: Pol- as 28°F. In order for plants to acclimate the acclimation period, and reduced lination). Flower sweetness readily at- to cold temperatures, they require proper photosynthesis can reduce food produc- tracts insects such as bees; bees vibrate/ hardening conditions: progressively tion. Pest damage or stress due to poor sonicate and loosen pollen, thereby cooler temperatures through autumn, cultural practices reduces acclimation spreading pollen from flower to flower followed by several mild freezing events. and maximum cold hardiness. Proper or self-pollinating flowers. Stigmas are Maximum cold hardiness is reached after pruning methods and timing (see Chap- only receptive to pollen for 3 to 6 days several days of sub-freezing tempera- ter 9: Pruning and Growth Management) after bloom. Pollinated flowers turn red tures. reduce stress. Avoid drought stresses and colored, while unpollinated flowers re- winter desiccation by providing sufficient main white. Each of several ovaries per water during the acclimation period, as flower requires pollination; the more that

4 Figure 2-2. Blueberry flowers in the early stage of bloom. Figure 2-3. Ripe blueberry fruit ready to harvest. are pollinated, the larger the fruit will de- culminating in about 85 percent water. Management). In addition to intolerance velop. Some cultivars are self-unfruitful, Consequently, drought reduces fruit size, for drought conditions, blueberry plants so cross-pollination increases fruit set for lowers starch content, and ultimately are also sensitive to standing water and these cultivars, also resulting in earlier results in lower sugar content. The riper root rotting pathogens; never plant fruit production and larger berries. the fruit, the shorter the postharvest shelf blueberry in flooding or heavy soil (see Overall, open flowers with exposed life, but storage at 32°F and 90 percent Chapter 11: Blueberry Diseases). Finally, stigmas are susceptible to a number of relative humidity can extend storage life blueberry plants are not aggressive com- potential problems. They are the least by up to 12-fold. petitors and do not compete well with cold hardy flower stage and can be easily weeds, especially when shrubs are young. damaged during extreme cold weather. Roots Therefore, weed control is of paramount Early blooming cultivars also risk poor Root growth begins in spring when importance when establishing a blue- pollination as cool spring weather limits soil temperatures reach 43°F, usually the berry planting (see Chapter 14: Weed bee activity. time buds begin to swell. Root growth Management). stops when fruit reach maturity and Fruit resumes again after harvest. In fact, Resources Blueberry fruit develop approximately during late summer and autumn, after Reproductive Growth and Development 2 to 3 months after bloom, dependent harvest and when soil temperatures drop of Blueberry (University of Florida), upon cultivar, weather conditions, below 60°F again, blueberry roots make http://edis.ifas.ufl.edu/pdffiles/HS/ and plant vigor. Overall, thicker canes most of their growth. Blueberries have HS22000.pdf. produce larger berries. Fruit is initially extremely fibrous root systems, which tart, but as fruit-acids are broken down require porous sandy or sandy loam during ripening, tartness is lost. Sugar is soil; their roots cannot extend through manufactured by leaves and transported compacted soil. Moreover, blueberry to berries. Sugar levels increase for several root systems are shallow, remaining in days after fruit turns blue. For the highest the top 8 to 12 inches of soil. Roots are quality fruit, berries should be allowed to contained primarily (90 percent) within ripen on plants (Figure 2-3); fruit flavor the dripline. Because they lack root hairs, and sugar content will not improve after blueberry roots are sensitive to drought harvest. Green fruit contain approxi- and changes to soil-water conditions. mately 7 percent sugar while mature This sensitivity to temperature extremes fruit contain approximately 15 percent and moisture fluctuations makes mulch sugar. Additionally, fruit size increases a critical practice in blueberry cultiva- up to 35 percent after fruit turns blue, tion (see Chapter 6: Irrigation and Water

5 Growth Stages

Dormant or tight bud Bud swell Bud break or bud burst Tight cluster Plant part: Flower bud. Plant part: Flower bud. Plant part: Flower bud. Plant part: Flower. Description: No visible swelling Description: First sign of growth Description: Flower buds open Description: Individual flow- of fruit buds. Bud scales tightly in spring. Visible swelling of the and individual flowers can be ers are distinguishable in flower closed. No visible signs of growth. flower buds; outer bud scales be- seen between bud scales. clusters. gin to separate at the tip revealing paler interior bud scales.

Early pink bud Late pink bud Full bloom Petal fall Plant part: Flower. Plant part: Flower. Plant part: Flower. Plant part: Flower. Description: Expanding flowers Description: Individual flowers Description: Most flowers on the Description: Corolla tubes are are readily visible and have sepa- fully developed. Expanded corol- bush have opened. falling off flowers, revealing small rated. Pink corolla tubes (petals) las are now white but still closed. green fruit. This is the most vul- are short and closed. nerable stage to freeze injury.

Early green fruit Fruit coloring Fruit bud set Fall color Plant part: Flower. Plant part: Fruit. Plant part: Shoot. Plant part: Shoot. Description: Small green berries Description: Oldest, largest fruit Description: After harvest the Description: At the end of the are expanding. Fruit in clusters in clusters begin to change color blueberry bush stores reserves growing season, leaves change vary from large to small pea- from green to pink to blue. Fruit for next year’s growth. Shoot color as nutrients are mobilized sized. Early fruit growth is by cell begins to soften. Cell division has growth may begin again. Flower back into shoots for growth next division. stopped and fruit growth is by buds for next year’s crop form in spring. cell expansion. September and October. These flower buds form first at shoot tips. These large, clearly visible buds can be used to estimate next year’s crop potential.

6 Chapter 3 after petal fall during a 2- to 5-week har- Types of vest season. Fruit can reach up to 1 inch diameter. Production varies from 4,000 to 10,000 pounds per acre, with reports Blueberries of up to 25,000 pounds per acre. Rabbiteye (Vaccinium virgatum; syn. and Cultivar V. ashei). Native to the Southeastern U.S., rabbiteye blueberries grow from North Carolina to northeastern Florida Selection and west to Mississippi and Louisiana. Figure 3-2. Rabbiteye blueberry planting. Plants may reach a height of 15 feet at maturity (Figure 3-2). Chilling require- axonomically, there are a number of ments, which are lower than highbush Tspecies of blueberries, but all belong types, vary from 350 to 650 hours. Bloom to the genus Vaccinium. Further, there occurs from 1 to 1½ weeks earlier than are many interspecific hybrids that are highbush types, and flower buds can sur- ° produced under artificially-controlled vive temperatures of -12 to -15 F. Bushes conditions. These hybrid selections can grow to 30 feet in height and produce include diploid, tetraploid, hexaploid, from 8,000 to 9,000 pounds per acre. Southern Highbush and heteroploid crosses. For practical (Vaccinium dar- purposes, however, this publication will rowi x V. virgatum). Southern highbush consider the four types (or species) of are hybrids with northern highbush and blueberries that are primarily used com- native southern varieties in their ances- mercially. try. Southern highbush varieties have Northern Highbush (Vaccinium cor- greater heat tolerance and a lower win- ymbosum). The most common type of ter chilling requirement than northern blueberry and the primary commercial highbush blueberries. Plants average 3 to blueberry in the Midwest is the northern 6 feet tall when mature. Flower buds can Figure 3-3. Lowbush blueberries. highbush (Figure 3-1). This species is na- survive mid-winter temperatures from ° ° tive to the eastern United States, ranging 10 F to -10 F, depending upon cultivar. from southern Nova Scotia to Wisconsin Growers in the southernmost ranges of commercially-grown blueberry in the and down the Atlantic coast to eastern the Midwest have been successful with northernmost regions of the U.S. The Texas. Plants, which prefer highly acidic, southern highbush; however, new grow- small deciduous shrub has a spreading organic soils, can reach 6 to 10 feet in ers should contact local Extension agents form; plants grow together in a 6- to 24- height at full maturity. Chilling require- or specialists for guidance. inch high thicket that is harvested with Lowbush ments vary from 650 to 900 hours, and (V. angustifolium, V. myrtil- hand rakes. Most of the fruit is used for flowers survive temperatures as low as loides). Native to the northeastern United processing, as opposed to fruit from -22° to -31°F. Fruit ripens 60 to 100 days States and parts of Canada, lowbush blue- highbush plants, which are primarily sold berry (Figure 3-3) is the most important on the fresh market.

a b c Figure 3-1. (a) Northern highbush blueberry planting, (b) Bluecrop variety, and (c) Bluetta variety.

7 Table 3-1. Northern Highbush Blueberry Varieties. Growing Fruit Picking Variety Season Zones Habit Size Scar Uses Comments Aurora very late 4-7 upright, M-VL S F P U New; moderate yields; latest ripening variety, can overbear; fruit firm, vigorous excellent flavor, tart if not fully ripe, good shelf-life Berkeley mid to 3-7 upright L L U Moderate yields; fruit firm, fair flavor, good shelf-life; powdery mildew late resistant, susceptible to Phomopsis stem canker Bluecrop early to 4-7 upright, L-VL S F P U High, consistent yields; can overbear; adapts to variety of sites; long mid open harvest period; drought resistant; fruit firm, high quality, resistant to cracking, limited shelf-life; very resistant to shoestring virus and moderately resistant to red ringspot virus, mummy berry, and powdery mildew, very susceptible to anthracnose Bluegold mid to 4-7 upright, M-L S F P U Moderate yields; easy to pick, concentrated harvest period, suitable late vigorous, for mechanical harvest; fruit flavor varies with site, firm, stem can stay small on berry; very susceptible to shoot phase of mummy berry but some resistance to fruit phase, moderate anthracnose resistance Bluejay early to 4-7 upright, M S F P U High yields; fast growth, easy to establish; suitable for mechanical mid vigorous harvest; fruit mild flavor, very firm, ships well, holds up well on bush; resistant to shoestring virus, moderate resistance to anthracnose, resistant to both phases of mummy berry Blueray early to 3-8 upright, L-VL M F U High yields; does well in hot summers, very cold winters; can overbear; mid open fruit dark, firm, out-standing flavor; susceptible to mummy berry, anthracnose, red ringspot virus Bluetta early 4-7 upright, M L F P U Moderate yields; late bloom; fruit tangy, dark color, fair flavor, short small shelf-life; susceptible to Phomopsis stem canker in the south Brigitta mid to 4-8 upright, M-L S Moderate yields; fruit tart, very firm, good shelf-life late spreading Cara’s mid 5-7 small, M S F U New; moderate yields; fruit hangs long on bush, outstanding flavor, dry Choice spreading scar, very firm; moderate resistance to mummy berry shoot phase but susceptible to fruit phase, moderately susceptible to anthracnose Chandler mid to 4-7 slightly VL S U Large yields, production variable; long harvest period; fruit very large, late spreading fair flavor Collins early to 4-7 upright, M S F Low yields; fruit with fair to good flavor, hangs long on bush; suscep- mid spreading tible to mummy berry Croatan early 3-7 vigorous, M-L L F U High yields; fruit medium firm, moderate flavor, ripens fast when hot; spreading moderately susceptible to Botryosphaeria stem blight (dieback), resistant to bud mite Darrow late 5-7 upright, L-VL M F High yields but inconsistent; fruit excellent flavor, firm; resistant to vigorous mummy berry and shoestring virus Draper early to 5-7 upright, L S F P U New; high yields; concentrated harvest period; fruit excellent flavor, mid vigorous, very firm; good shelf-life, easy to pick; some susceptibility to mummy stocky berry Duke early 4-7 upright, L S F P U Consistently large yields; concentrated harvest, suitable for mechani- stocky cal harvest; blooms late; needs very good growing site; fruit firm, mild, sweet, holds up well on bush; moderately resistant to twig blight, susceptible to Botryosphaeria stem blight (dieback), moderately susceptible to mummy berry fruit phase Earliblue very early 5-7 upright L M F P U Moderate yields, the first to ripen; plant where well suited; erratic fruit set; fruit fair flavor, firm, hangs long on plant, resists cracking, ships well; moderate powdery mildew resistance, susceptible to Phomopsis stem canker Elliot very late 4-7 upright S-M S F U P High yields; blooms late, can overbear, suitable for mechanical harvest, pick fully ripe; fruit small, tangy, resists cracking, stores well; resistant to powdery mildew and shoot phase of mummy berry, susceptible to fruit phase of mummy berry, resistant to anthracnose Hannah’s early 5-7 upright, M-L S F New; moderate yields; fruit mild, excellent flavor, firm, sweet, size Choice vigorous decreases as harvest progresses; some resistance to both phases of mummy berry, moderate anthracnose resistance Hardyblue mid 4-7 upright, M P Moderate to large yields; adapts to heavier soils, suitable for mechani- vigorous cal harvest; fruit dark, very sweet, outstanding quality Herbert late 4-7 small, VL M U Moderate yields; hangs long on plant; fruit dark, soft, thin skin, wet spreading scar; some susceptibility to mummy berry shoot phase, moderately resistant to fruit phase Jersey late 4-7 upright, S-L M F P U High yields; occasionally small fruit due to poor pollination, easy to vigorous establish, tolerates variety of soils; suitable for mechanical harvest; fruit firm, dark, good shelf-life; moderate anthracnose and red ringspot virus resistance, some resistance to both phases of mummy berry continued

8 Table 3-1. Northern Highbush Blueberry Varieties (continued). Growing Fruit Picking Variety Season Zones Habit Size Scar Uses Comments Liberty late 4-7 upright, M-L F P U New; moderate yields; adaptable to variety of conditions; concentrated vigorous harvest, suitable for mechanical harvest; fruit distinctly flavored, easy to pick, very firm Nelson mid to 4-7 upright, M-L S F P U Moderate yields; fruit firm, very good flavor late spreading Patriot early 3-7 short, L S U F Consistently high yields; blooms early; adapts to many soils, may do spreading better in wetter soils; fruit firm, slightly tangy, dark, very good flavor; moderate Phytophthora root rot resistance, moderate resistance to both phases of mummy berry Reka early 4-8 upright, M-L P U Large yields; adapts to variety of soils, adapted to northern climates; vigorous suitable for mechanical harvest; fruit outstanding flavor, dark; moderately resistant to both phases of mummy berry, some resistance to anthracnose Rubel mid to 4-8 upright S M P Consistently large yields; suitable for mechanical harvest; fruit very late sweet, outstanding flavor; moderately resistant to Phomopsis stem canker, susceptible to mummy berry, and moderately susceptible to anthracnose Sierra early to 4-7 upright, L S F P U Moderate to large yields; does well on some sites; suitable for mechani- mid spreading cal harvest; fruit firm, good flavor; moderately anthracnose resistant, some susceptibility to both phases of mummy berry Spartan early 5-7 upright, VL M U Moderate to large yields; sensitive to high pH, requires light soils with vigorous high organic matter; blooms late; suitable for mechanical harvest; fruit firm, easy to pick, outstanding flavor; moderate resistance to both phases of mummy berry, susceptible to anthracnose Toro early to 4-7 spreading, M-VL S F U Moderate to large yields, concentrated harvest; slow growing; fruit mid stocky outstanding quality, easy to pick; some resistance to both phases of mummy berry, moderately resistant to anthracnose Abbreviations: Fruit Size: S = small, M = medium, L = large, VL = very large Picking Scar: S = small, M = medium, L = large Uses: F = sold fresh, P = for processing, U = u-pick

Table 3-2. Southern Highbush Blueberry Varieties. Growing Fruit Picking Variety Season Zones Habit Size Scar Uses Comments Arlen late 6-10 upright M-L S F Moderate yields; suitable for mechanical harvest; fruit good flavor and shelf-life; Botryosphaeria stem blight (dieback) and mummy berry resistant Bladen early 6-10 upright, M S F Suitable for mechanical harvest; fruit firm, resists cracking vigorous Carteret early to 6-9 upright, S-M S F New; high yields; adapts to variety of soils, suitable for mechanical mid vigorous harvest; fruit very good quality, good shelf-life Legacy mid to 5-10 upright, M-L S F P U Consistently large yields; blooms early, long harvest period, suitable late vigorous, for mechanical harvest; fruit holds up well on bush, outstanding flavor; spreading resistant to anthracnose, some resistance to both phases of mummy berry Lenoir mid 6-10 vigorous, M S F P New; moderate yields; needs well-drained soil, suitable for mechanical spreading harvest; fruit firm, very good flavor, good shelf-life; excellent disease resistance Misty early 5-10 upright, M-VL S F Consistently high yields; can overbear, long harvest period, suitable for vigorous, mechanical harvest; fruit very firm; susceptible to Botryosphaeria stem spreading blight (dieback) O’Neal very early 5-10 upright, L S F U Moderate yields; sensitive to high pH, early long bloom makes it a spreading good pollinizer; fruit very firm, outstanding flavor Ozarkblue mid to 4-9 upright, M-L S F P Moderate yields; tolerates hot weather, drought resistant, late bloom, late vigorous long harvest period; fruit firm, fair to excellent flavor; resistant to spreading powdery mildew, some susceptibility to Botryosphaeria stem blight (dieback) Pamlico early 6-10 vigorous, SS New; high yields; into production quickly, suitable for mechanical tomid spreading harvest; fruit good shelf-life, good flavor; Botryosphaeria stem blight (dieback) resistant continued

9 Table 3-2. Southern Highbush Blueberry Varieties (continued). Growing Fruit Picking Variety Season Zones Habit Size Scar Uses Comments Reveille very early 5-10 upright, M-L S F U Consistently moderate yields; early bloom, adapts to variety of soils, narrow suitable for mechanical harvest; fruit firm, crunchy, may crack in rain; moderately Botryosphaeria stem blight (dieback) and anthracnose resistant Star early 6-10 upright, L F New; moderate yields; early bloom, low chill, concentrated harvest, spreading suitable for mechanical harvest; fruit firm, dry scar, good flavor, excellent quality, may split in rain; susceptible to Septoria, resistant to Phytophthora root rot and to Botryosphaeria stem blight (dieback) Summit mid to 6-10 spreading L S New; high yields; blooms late; fruit excellent flavor, good shelf life, late resists cracking Abbreviations: Fruit Size: S = small, M = medium, L = large, VL = very large Picking Scar: S = small, M = medium, L = large Uses: F = sold fresh, P = for processing, U = u-pick

Table 3-3. Northern Half-high Varieties. Although these can grow in a range of hardiness zones, they were developed for northern production areas. Half-high varieties reach a maximum of height of 3 feet or less. Growing Fruit Picking Variety Season Zones Habit Size Scar Uses Comments Chippewa mid 3-7 small M-L S F Moderate yields; fruit firm, very sweet; excellent disease resistance Northblue early to 3-7 upright, M-L M F Low yields; good quality fruit, wild flavor; resistant to mummy berry mid small North- early to 3-7 very small M M U F Low yields; adapts to variety of soils, bears in 2 years country mid Northland early to 3-7 upright, S-M M P High yields; most hardy northern highbush, adapts to variety of soils mid small, and sites; fruit firm, soft, dark, very sweet, wild flavor; resistant to spreading shoestring virus Northsky early to 3-7 very small S-M M F U Low yields, good shelf-life; resistant to mummy berry mid Polaris mid 3-8 upright, M S F P Moderate yields; requires sandy, acid soil; fruit sweet, tart; excellent small disease resistant St. Cloud early to 3-5 small M S Moderate yields; fruit good flavor, good shelf-life mid Abbreviations: Fruit Size: S = small, M = medium, L = large, VL = very large Picking Scar: S = small, M = medium, L = large Uses: F = sold fresh, P = for processing, U = u-pick

Cultivar Selection If specific microclimates allow for other dates can result in a continuous supply There are numerous high quality blueberry types, growers should contact of fresh berries throughout the fruiting highbush blueberry cultivars available local Extension offices or state specialists season. in the commercial trade due to strong for more information. Some blueberry plants are self-com- Desirable Qualities. breeding efforts in the United States. Desirable fruit patible and can set economical crops Blueberry growers are encouraged to characteristics are large size, light blue without cross-pollination with another check with local Extension profession- color, firm fruit, crack resistance, high cultivar. However, planting fields with als and other growers in their state or storage quality, and pleasant aroma and two cross-compatible cultivars can result region for local performance of various flavor. Additional desirable characteris- in larger berries and higher yield. Before blueberry cultivars. Keep in mind that tics include the tendency for fruit to re- planting, carefully research compatible vigorous or high-producing cultivars in main attached to plants rather than drop cultivars to plant together and consider one state may not be productive in other at ripening and presence of a small, dry the logistics of having multiple cultivars states, as climate and soil conditions vary fruit scar that lessens decay after harvest. in a field. If it is economically beneficial to Maturity. throughout the region. Blueberry cultivars also dif- plant more than one cultivar in the same This section discusses some of the fac- fer in time of ripening. As a rule, berries field, select those that bloom at the same tors that growers should consider when ripen 60 to 100 days after bloom. Berries time. Growers should group cultivars by selecting blueberry cultivars. Highbush on each blueberry bush do not ripen all ripening dates so that harvest will prog- blueberry cultivars are the focus of this at once, resulting in each bush supplying ress in an orderly fashion. For example, production guide, since they are the pre- fresh fruit for a 2- to 3-week period. Se- Duke and Spartan are popular early- dominant blueberry type in the Midwest. lection of cultivars that differ in ripening season cultivars; Bluecrop, Draper, and

10 Toro are common mid-season cultivars; late-maturing cultivars, and therefore, also harvest blueberries by machine. If and Nelson, Darrow, and Elliott are often early maturing cultivars are consequently berries are to be machine-harvested, suitable late-season cultivars. Various more prone to frost injury. One exception growers should choose suitable cultivars other combinations are possible and new is Patriot, which ripens later than Duke, with an upright growth habit. Those cultivars are released regularly. Consider but blooms earlier. Blossoms of highbush cultivars that ripen fruit over a relatively bloom and ripening time, compatibility, cultivars withstand temperatures of ap- long period or have berries that drop as and productivity of the cultivar options proximately 28°F when plants are in full soon as they ripen are not suitable for me- for your region. bloom. chanical harvest. For best results, berries Frost Hardiness. Spring frost hardiness Harvest Method. Many blueberry should hang on bushes for a longer period is based upon developmental stages of growers in the Midwest sell fresh berries of time, but drop off once the mechanical flowers, which varies per cultivar. Earlier though a pick-your-own operation. How- harvester shakes the bush. maturing cultivars bloom earlier than ever, most large-scale blueberry growers

11 Chapter 4 have grown fruit in a given area can help Table 4-1. Critical Cold Temperatures for Blueberries. potential producers avoid frost pockets. Site Selection Growth Stage Critical Cold Temperature The most frost-free sites are those Bud swell 10° to 15°F (-12° to -9°C) with higher elevations than surrounding Tight cluster 20° to 23°F (-7° to -5°C) areas, since cold air drains from higher Early pink bud 23° to 25°F (-5° to -4°C) he best blueberry planting sites are to lower areas. Avoid planting in low Late pink bud 24° to 27°F (-4.4° to -2.8°C) Tthose with full sunlight, low late-frost areas because cold injury is often greater, Full bloom 28°F (-2.2°C) risk, and good soil drainage. Selection of a resulting in reduced yields in these sites. Petal fall 32°F (0°C) site with desirable climatological charac- Generally, sites with steep slopes (10 teristics helps reduce cultural problems percent or more) should be avoided in and assures success of the planting. commercial plantings because of soil loss during summer. Furthermore, since Climate erosion and difficulty in operating equip- bees are negatively influenced by exces- ment. Slopes of 3 percent to 5 percent are sive wind, reducing wind flow favors bee General climatic conditions in many often ideal, as they promote water and air flight in the planting. Windbreaks should regions of the Midwest are favorable for drainage and reduce risk of frost injury. be porous, so that winds are slowed by growing blueberries. Cultivars should be Cool temperatures on northern approximately 50 percent. This still per- selected according to climatic constraints slopes often delay plant growth enough mits good air circulation in the planting, such as minimum temperatures and in spring to reduce spring frost damage. as this air movement helps dry dew and length of growing season. Additionally, However, these slopes may be subject rain from the foliage, thereby reducing climate may influence disease, insect, to more harsh winter conditions. The disease problems. and other pest problems, which will vary opposite effect may occur on a southern Frost and Freeze Damage due to the differing climatic conditions slope, resulting in earlier spring growth within the Midwestern region. and increased risk of frost injury from Low temperatures during mid-winter Topography late frost. A western slope may have the often are not fatal to blueberry; however, disadvantage of exposure to prevailing fluctuating early spring temperatures can Monitoring or mapping site condi- winds that, in some areas, may be strong be detrimental to plantings and reduce tions before planting is recommended. enough to damage plants. yield (Figures 4-1 and 4-2). As plants Any prior knowledge of an area’s eleva- If cold sweeping winds are com- break dormancy and flower buds begin tion effects and other conditions may mon during winter, windbreaks may be to open, they are more sensitive to cold help producers locate plantings above needed. Sheltering plants from wind not temperatures (Table 4-1). Thus, sites with frost pockets and avoid damaging sea- only protects them in the winter, but also good air drainage and proper cultivar sonal frosts. Advice from those who leads to reduced desiccation and water selection are critical.

Figure 4-1. Blueberry flowers with frost-damaged pistils. Figure 4-2. Young blueberry fruit damaged by frost.

12 Air Drainage Air drainage refers to the movement of air from tops to bottoms of hills. A slight slope is ideal for good air movement. Trees and brush should be cleared from the slope to allow cold air to drain away. Air movement helps reduce spring frost injury, especially at lower elevations. Cold air should not be allowed to stagnate. Air movement also assists in the drying of fruit and foliage. Various diseases, such as gray mold and anthracnose fruit rot, are favored by high humidity and wet plant tissue (see Chapter 11: Blueberry Diseases). Soils and Water Drainage A location with a permeable soil texture that has good internal and surface drainage is required for vigorous plant- Figure 4-3. Low areas, such as bottoms of slopes, are susceptible to water accumulation and root rotting diseases. The lower portion of this field is infected with Phytophthora root rot, ings. Water drainage means removal of caused by water accumulation during rainy seasons. surface water, as well as percolation or internal movement of water. With good management, blueberry plantings can and yields may not be satisfactory. In To assess internal drainage capacity, produce satisfactorily on soils ranging addition, just as cold air should not be examine sites during winter after a heavy from gravelly loams to silt clay loams. allowed to stagnate on a planting site, rain. Ideally, no standing water should The USDA Natural Resources Con- neither should water be allowed to ac- remain after 24 hours. Drain tiles or servation Service (NRCS) has mapped cumulate (Figure 4-3). Avoid planting perforated, corrugated pipe may be used most of the soils in the Midwest. Before bushes in areas where water ponds or below soil surfaces, but they should be producers establish plantings, they puddles for extended periods following installed prior to planting. If the general should contact the local NRCS office a rain. Phytophthora root rot can be a topography (elevation, slope, etc.) is favor- to obtain county soil survey maps and severe problem in wet sites (see Chapter able, but internal drainage is imperfect, examine soil conditions in the proposed 11: Blueberry Diseases). a drainage system should be considered. site. Soil maps are helpful in determin- Subsoil characteristics are important Tile drainage or perforated pipe drainage ing soil-drainage characteristics and in when choosing a site because they often improves most sites for the production evaluating potential sites. However, maps indicate the nature of internal drain- of the majority of fruit crops. Producers are not substitutes for taking soil samples age. For example, bright, uniformly should carefully examine these condi- of the site and making visual evaluations yellowish-brown subsoil often indicates tions before blueberries are planted. of the subsoil. good internal drainage. Subsoils show- Most university Extension specialists Growers should avoid soils that are ing slight mottling of yellow, gray, and recommend that blueberries be planted consistently wet. These soils may have orange indicate only moderate drainage. on raised beds or mounds for improved impervious subsoils or other drainage Poorly drained subsoils are characterized drainage. Planting on raised beds is just problems. Roots may remain shallow in by greater mottling or, in some cases, a as effective or often more effective as poorly drained soil, whereas they should uniform dark-gray color. Soils should drainage systems and considerably less penetrate 12 to 18 inches in a deep, well- contain at least 3 percent organic matter. expensive. Mounds or beds should be 8 drained soil. Soils with only moderate In addition to contribution of nutrients, to 18 inches high and built with loamy drainage characteristics require more organic matter improves soil texture and soil amended with organic matter. intensive soil management (e.g., tiling), improves internal drainage.

13 Chapter 5 Planting and Establishment

reparation of a proposed blueberry Psite should begin at least 1 year before planting. Site preparation at this time should include land leveling, drain tile installation (when needed), application of organic matter, and fertility adjustments Figure 5-1. Incorporation of peat moss into Figure 5-2. Incorporation of peat based on a soil tests. The soil test should raised beds. moss into raised beds. provide information on soil pH status as well as sulfur and fertilizer requirements (see Chapter 10: Soils, Fertilization, and Nutritional Disorders). Site Preparation Adjusting Soil pH. If soil pH is high, apply elemental sulfur to lower pH to a more desirable level (4.5 to 5.0). The application should be made at least several months before planting. Additionally, calcium levels will affect soil pH. If soil tests indicate that calcium levels are greater than 2,500 pounds per acre, it will be difficult to maintain a low pH Figure 5-3. Peat moss is available in large, Figure 5-4. Plants are available as container- in the desirable range. Thus, it may be a compressed bales. grown stock plants (shown) or as bare root good idea to consider a crop other than liners (not shown). blueberry. Adding Organic Matter. Organic matter content should be above 3 percent. Peat moss, composted pine bark or composted sawdust should be incorporated (Fig- ures 5-1 to 5-3), and then used as a mulch to improve organic content. As sawdust or other wood products decompose, soil nitrogen is often temporarily unavailable. Addition of supplementary nitrogen and monitoring of soil nutrients is essential, so amendments should be made before planting. Use only composted sawdust, as fresh sawdust could lead to severe nitrogen deficiencies and possible plant death. A preplant cover crop is recommended the year before orchard planting. Figure 5-5. Plants should be watered immediately upon delivery and kept moist until instal- In addition to improvement of organic lation. matter content, cover crops suppress weeds and improve soil structure. Ani- mal manures, when available, may be matter, but they may raise the soil pH. Weed Management. Prior to planting, applied in autumn before spring planting. A suitable application is 10 to 12 tons of growers must manage persistent weed They provide both nutrients and organic horse or cow manure per acre or 50 to 75 pests, such as thistle, Johnsongrass, pounds per 100 square feet. quackgrass, dock, and woody species,

14 Figure 5-6. A new blueberry planting with recently-installed bushes Figure 5-7. Proper spacing allows plants room to grow. (background) and prepared beds that are ready for planting (fore- ground). such as poison ivy and brambles (see have the advantage of higher transplant is dry enough to work properly. If soil is Chapter 14: Weed Management). Several success rate, but they are more expensive. worked while wet, soil structure may be safe and effective herbicides are available Plants in containers can be kept outdoors damaged. Effects of compaction and a to control such troublesome weeds dur- until planting, as long as they are watered puddled soil, particularly one with high ing site preparation, but they cannot be and protected from extreme environ- clay content, may result in poor plant used after bushes are planted. If possible, mental conditions (heat, cold, hail, etc.) growth for a number of years. avoid sites that are severely infested with (Figure 5-5). Container plants, if actively Planting Layout. Blueberry plantings such weeds until they have been eradi- growing, can be set in the field after the should be designed to achieve the follow- cated. Once raised beds are developed, threat of frost and freeze have passed. ing goals: grass middles may be planted using a Bare root plants are shipped in a dormant • Prevent soil erosion. mix of fescue or creeping red fescue and state and should be kept under refrigera- • Use land area efficiently. ryegrass in August or September prior to tion until planting. They are sensitive to • Optimize plant performance. autumn or spring planting. Final weed desiccation and should not be allowed to • Facilitate management and equipment removal may also be necessary just before dry out. Bare root plants can be set in the operation. planting. field once received, generally in the late Row spacing is typically 10 to 12 feet winter or early spring. between rows and 3 to 5 feet between Planting Timing. For best results, blueberry plants within a row (Figure 5-7). About Planting Material. Proper handling of bushes should be planted in autumn into 1,450 plants per acre are installed at a plant material once received from the well-prepared beds (Figure 5-6). Spring spacing of 10 feet by 3 feet. Plant and nursery is important. Typically, blueberry installation is also acceptable, as long as row spacings may be adjusted for larger plants are 2- to 3-years old and are avail- spring rains do not delay planting into or smaller cultivars. able in either in containers (pots, Figure the warmer months. Spring preparation 5-4) or bare root. Container-grown plants should not be performed until the soil

15 Chapter 6 Some negative aspects of drip irriga- Irrigation tion include: dust cannot be washed off fruit using irrigation water, plants cannot be cooled by irrigation on hot summer and Water days, frost protection is not possible, cover crops cannot be irrigated, and Management maintenance to prevent emitters from clogging is time-consuming and difficult to monitor. Initially, one emitter per plant is suf- lueberries have fine roots that are ex- ficient, but addition of a second emitter Btremely shallow-rooted, thus, plants is often required as the plants mature are highly susceptible to drought stress (Figure 6-2). One emitter on each side (Figure 6-1). Root systems of established Figure 6-1. Symptoms of drought stress on of individual bushes is required because plants are within 18 inches of the soil blueberry foliage. blueberry plants cannot laterally trans- surface, while roots of young plants are locate (move within the plant) water or within the top 12 inches of soil. Soils with plants are already stressed. Supplemental most nutrients. Therefore, if only half the hard pans result in even more shallow irrigation should always be applied before root system receives water or fertilizer, root systems, and thus, plants become wilting occurs. only half of the top portion benefits. It is more sensitive to drought conditions. important for drip-irrigated fields to have Supplemental watering (1 to 1.5 inches Types of Irrigation a uniform water supply. water per week), especially from fruit Either sprinkler or drip irrigation Do not place emitters near centers expansion through harvest, is often systems may be used to irrigate blueberry of crowns as water may puddle in this required. plantings. area, producing conditions favorable for Drought conditions can result in the Drip Irrigation. Producers that have Phytophthora root rot (see Chapter 11: following types of damage to plants and small plantings with a limited amount Blueberry Diseases). Also, in fields newly fruit: of water availability or low water pres- planted with container stock, emitters • Root damage and plant decline: Recov- sure may choose drip systems. Overall, should be placed near edges of media so ery may be difficult for less vigorous drip irrigation systems are more efficient that lighter soil of the potting medium plants. than sprinkler systems; there is less water wets before water moves into heavier • Fruit cracking: During periods of loss and soil remains evenly moist. When surrounding soil. Once emitter systems drought, skins of expanding fruit combined with mulch, this method is have been installed, they should not be become dry. Following rain or irriga- most beneficial to plants. Fertilizers and disturbed, as roots will grow predomi- tion, fruit swell faster than skins can some soil drench pesticides may be ap- nantly in wetted zones. accommodate and then split. plied through drip irrigation. • Reduced bud set: Flower initiation for the following year begins during midsummer. Water stress reduces bud set the subsequent year.

Different soil textures have different water-holding capacities. Water loss from soil and through plants can be up to 0.25 to 0.60 inches per day, depending upon temperatures, plant size, and soil texture. Some sandy soils may hold less than 1 inch of available water; loamy soils can hold about 2 inches. Thus, available water may be depleted from soils in as little as 2 days during hot, dry conditions. Irriga- tion schedules must take water losses into account to prevent plant damage. Blueberries have thick leaves and wilting is not always apparent, but wilted foliage and/or shriveled berries indicate that Figure 6-2. Drip tape should include at least two emitters per plant in order to provide even watering.

16 Sprinkler Systems. Overhead sprinklers (Figure 6-3) offer a number of advantages in addition to irrigation. These include: cooling plants during hot weather and providing frost/freeze protection (Fig- ure 6-4) when temperatures drop below freezing during bloom. Overhead irrigation can provide cold protection to plants when temperatures drop as low as 24°F. Overhead irrigation can also be used to maintain soil moisture in cover crops planted between rows. Sprinkler systems are not prone to clogging and require little maintenance. Consider, however, that risers of sprinklers may interfere with machines on fields that are machine Figure 6-3. Overhead irrigation consists of Figure 6-4. Overhead irrigation can provide harvested. nozzles mounted onto risers. frost protection during early spring. When considering sprinkler system design, calculate amounts of water emitted by individual sprinkler nozzles to determine spacing. Nozzle size and water pressure are used to determine spacing. Consider that 20 percent to 30 percent of water from overhead sprinkler systems may be lost to evaporation, and operating times should be adjusted ac- cordingly. Additionally, sprinkler systems usually have only 70 percent uniformity, so in order to sufficiently cover all areas of a planting, 30 percent more water than calculated should be applied. Mulch Benefits of Mulch. Blueberries often grow better in mineral soil when mulched, although many successful plantings have no mulch. Mulching to a Figure 6-5. Sawdust is commonly used for mulch, but it can have negative effects if not man- depth of 5 to 6 inches on soil surfaces of aged properly. mature plantings keeps soil cool, helps conserve soil moisture, adds organic matter to soil, improves soil structure, and aids in preventing annual weeds from becoming established. Mulch is less effective against perennial weeds. Blueberry roots tend to grow in mulch, as well as in soil. Thus, as mulch decomposes, roots may become exposed. Mulch should, therefore, be maintained by adding 2 to 3 inches every 2 to 3 years in a 3 to 4 foot band underneath plants. Types of Mulch. Sawdust is commonly used as mulch for blueberries (Figure 6-5), although it is often discouraged. Sawdust mulch can provide winter habi- tat for rodents, which can create tunnels Figure 6-6. Sawdust should be composted Figure 6-7. Woven propylene fabric can be for at least 1 year before use as mulch. used as mulching material.

17 under root systems and eat bark from additional 50 percent to 100 percent N Weed matting, consisting of a woven young canes. If applied in thick layers, may be necessary for the first few years polypropylene fabric (Figure 6-7), is also sawdust can hold excessive amounts of to compensate for increased microbial used successfully as a mulching material water, or it can crust over and reduce activity and nitrogen consumption. Thus, in some regions (e.g. Michigan). Water water penetration. Growers who use soil tests are critical to a balanced nutri- easily passes through mats. Edges must sawdust as mulch should prepare to tional program (see Chapter 10: Soils, be covered with soil to keep the weed reapply often, as it decomposes quickly. Fertilization, and Nutritional Disorders). mat in place. On wet sites, weed matting Despite the challenges of using sawdust Other organic materials (e.g. tree trim- can hold excess moisture and can lead to as mulch, strict field management can ming chips and pine needles) work well losses from soil-borne diseases such as overcome possible problems. However, as mulch substrates. However, straw and Phytophthora root rot (see Chapter 11: non-composted sawdust should never deciduous leaves are not recommended, Blueberry Diseases). be used. If not well composted, sawdust as they tend to pack, thus preventing ad- can tie up nitrogen (N) and cause severe equate water penetration. Straw decom- Additional Resources nutrient deficiencies that can lead to poses quickly and must be replenished Northwest Berry and Grape Information plant death. Stockpile sawdust at least more often than most mulch types. Network, USDA-ARS, Oregon State 1 year prior to spreading, if possible, for Black plastic has been used effectively University, University of Idaho, and sufficient breakdown (Figure 6-6). Pine as mulch in some areas. If plastic mulch Washington State University, http:// sawdust (composted, not fresh) usually is considered, drip irrigation tubes must berrygrape.org. has little effect on soil pH. On the other be placed underneath plastic. Fertilizer Strik, B., C. Brun, M. Ahmedullah, A. hand, hardwood sawdust increases pH application can be more difficult when Antonelli, L. Askam, D. Barney, P. by releasing calcium as it breaks down. plastic mulch is used. Plastic usually Bristow, G. Fisher, J. Hart, D. Havens, R. Soil pH should be monitored on a yearly deteriorates after 2 to 3 years. Disposal Ingham, D. Haufman, R. Penhallegon, basis if hardwood sawdust is used. An of plastic can be problematic, especially J. Psheidt, B. Scheer, C. Shanks, and R. from an environmental standpoint. Williams. 1993. Highbush blueberry production. Oregon State University Pacific Northwest Extension Publica- tion 215.

18 Chapter 7 Pollination

lueberries are capable of setting fruit Bon 100 percent of flowers, although 80 percent set is considered a full crop. Because blueberry pollen is sticky and heavy, it is not easily transported by wind; therefore insects, especially bees, are needed to visit flowers so high fruit set and berry size can be achieved. Figure 7-1. Bumblebees are efficient pol- Figure 7-2. Honeybees do not pollinate as Pollination and Pollinators linators. efficiently as bumblebees, but hives can Blueberry pollen is shed from pores in provide large numbers of pollinators during flowering. anthers onto bodies of bees as they feed on nectar inside flowers. Bumblebees (Figure 7-1) and other specialized wild more attractive. Evidence suggests that One strong hive (minimum of 45,000 solitary bees are capable of “sonicating” attractive cultivars produce more nectar bees) is sufficient for 2 acres of Rancocas or vibrating pollen from anthers, loosen- than those that are less attractive to bees. and Rubel; one hive per acre for Wey- ing pollen for easier dissemination. Maintaining dense native plantings mouth, Bluetta, Blueray, Pemberton, and Honeybees (Figure 7-2) are not as ef- along perimeters of blueberry plantings Darrow; three hives for every 2 acres of ficient as bumblebees in pollinating blue- encourages nesting by wild bees, which Bluecrop; two hives per acre of Stanley, berry flowers. They forage less when the aid with pollination. However, wild bees Berkeley, Coville, and Elliott; and five temperatures are cool, the day is overcast, cannot always be depended upon for hives per 2 acres of Jersey and Earliblue. or the wind speed is high. Compared to pollination because of inadequate or fluc- These recommendations were developed wild bees and bumblebees, honeybees tuating population numbers. One rule of in the 1980s, and growers with high- begin flying later in the morning and re- thumb is that four to eight bees should be yielding fields are using additional hives turn to their hives earlier in the evening. foraging on each blueberry plant at any to help ensure maximum yields. Honeybees do not sonicate blueberry one time during the warmest part of the flowers and rarely collect much blueberry day during bloom. When wild pollinators Protecting Pollinators pollen. are not abundant, honeybee hives should Growers should be aware of the Carpenter bees can be problematic be introduced into the area. importance of pollination in blueberry during pollination, as they pierce holes culture and make every effort to protect in flowers during nectar collection, and Hive Placement honeybees and native bee populations. no pollination occurs. Moreover, other Hives should be in place when about Never use bee-toxic insecticides dur- bees often feed through these holes and, 5 percent of flowers have opened, but no ing bloom. Bee colonies should have a thus, carry out no pollen in the process. later than 25 percent of full bloom. They pesticide-free source of water nearby. This is especially problematic in flowers should remain in plantings until petals Arrangements should be made with with long corollas (petals). begin to drop. Hives should be placed beekeepers in advance to remove hives Flowers with short corollas are more in wind-sheltered, sunny locations with before bee-toxic insecticides are applied easily pollinated than those with longer their entrances facing east. Bees become after bloom. corollas. Some attribute the consistent active sooner if facing morning sun. Poor Fruit Set fruit set of Bluecrop to its shorter corolla, Distribute hives evenly throughout plant- and poor set of Earliblue to its longer ings to maximize probability of flower If fruit set is poor, gibberellic acid corolla. Cultivars also vary in their ability visitations. Bees fly further along rows sprays can be applied to increase set. to attract pollinators. Earliblue, Stanley, than across them. Place hives 300 feet This hormone induces parthenocarpic and Coville are relatively unattractive to apart along every tenth row. Competing fruit set (seedless berries), but results in bees, whereas Rubel and Rancocas are flowers should be eliminated (e.g. mow smaller, later maturing fruit. the dandelions).

Reprinted from Strik, B., C. Brun, M. Ahmedullah, A. Antonelli, L. Askam, D. Barney, P. Bristow, G. Fisher, J. Hart, D. Havens, R. Ingham, D. Haufman, R. Penhallegon, J. Psheidt, B. Scheer, C. Shanks, and R. Williams. 1993. Highbush blueberry production. Oregon State Univ. Pacific Northwest Ext. Pub. 215. Adapted for the Midwest.

19 Chapter 8 Commercial blueberry bushes are Hardwood Cuttings Propagation typically propagated asexually, usually Collecting and Storing Cuttings. The by hardwood cuttings. Plants may also first step for propagation of blueberries be asexually propagated by softwood by hardwood cuttings is collection of cuttings, but hardwood cuttings are less ost blueberry plantings are estab- 12-inch to 30-inch shoots or “whips” perishable and easier to handle. However, from healthy, true-to-type mother plants. Mlished with nursery-propagated some cultivars are difficult to root by plants, saving growers the time and Shoots should be from the previous sea- hardwood cuttings and may root more son’s growth and collected while plants investment involved in propagation. easily by softwood cuttings (e.g. Bluecrop, However, if growers are able to delay are dormant in late winter or early spring. Darrow, Herbert, Ivanhoe, and Stanley). Avoid highly branched shoots, shoots planting for an additional season or Plants may also be sexually propagat- prefer to produce their own plants, the with flower buds, and shoots that devel- ed by seed; however, resulting plants will oped late during the previous growing following basic knowledge of blueberry not be true-to-type. Breeders use sexual propagation should be helpful. season. Growers should take precau- propagation to develop new cultivars. tions to confirm cultivar labeling before taking cuttings; many off-types appear in plantings due to improper identification. Cut shoots into 5- to 6-inch lengths; each cutting should be about 1⁄4 inch in diameter and have 4 to 6 buds. About fifty cuttings may be placed in a plastic bag with moist (not wet) paper towels or moist sphagnum peat moss. Bags may be stored for several weeks in a refrigerator or area where the temperature is maintained between 35° and 40°F. Figure 8-1. Blueberry cuttings set in a Figure 8-2. Blueberry cuttings set in a propagation bed; some have started to propagation bed showing overhead mist leaf-out. system.

Figure 8-3. Blueberry cuttings in propagation boxes on the floor of a Figure 8-4. Blueberry cuttings in propagation containers on benches greenhouse with a mist system. in a greenhouse with a mist system.

20 of each cutting should point downward to prevent moisture from condensing on without touching the bottom of the box. cuttings. Also, an intermittent mist sys- Difficult-to-root cultivars can be dipped tem is more critical for keeping softwood into rooting hormone prior to planting. cuttings moist than it is for hardwood Keep cuttings moist by placing them un- cuttings. der an intermittent mist system (Figures 8-1 to 8-4). Cuttings should be misted Tissue Culture every 3 to 5 minutes for 6 to 8 seconds Blueberry plants may also be propa- for about 6 hours per day until rooting gated by using tissue culture techniques, occurs. often referred to as micro-propagation. Figure 8-5. Potted blueberry plants that Cuttings may be rooted outdoors, in Half-inch long sections of stems, each have been transferred from a propagation high tunnels, or in greenhouses. High containing a bud or growing tip, are bed. tunnels and greenhouses offer greater sterilized and then transferred using control over temperature and humidity sterile techniques into an agar-based me- Propagation Mixes. Root cuttings in a than outdoor settings, while also provid- dium. After a few weeks, newly formed potting mixture that is well drained yet ing protection from adverse environmen- plantlets are transferred onto rooting retains moisture. Examples of suitable tal conditions. media and grown under high-humidity potting mixes include sand and sphag- After root development, cuttings conditions in greenhouses in trans- num peat moss (1:1), peat and vermicu- may be overhead sprinkle-irrigated un- plant trays. Tissue-cultured plants are lite or perlite (1:1), or perlite, sand, and til they are ready to be transferred into extremely tender and should be slowly vermiculite (1:1:1). Sphagnum peat moss individual pots (Figure 8-5) or set out acclimated to outdoor conditions before must be thoroughly wetted prior to mix- into the nursery. Rooted cuttings with they can be transplanted into fields. Due ing with the other parts of the media. new leaves should be fertilized with a to the expensive laboratory equipment Propagation Beds/Containers. Propa- complete form of slow-release fertilizer required, growers often purchase micro- gation mixtures are usually placed into and supplemented with an ammonium propagated plants from producers who propagation beds (Figures 8-1 and 8-2) or form of nitrogen (N) to maintain active specialize in this method of propagation. boxes (Figures 8-3 and 8-4) that are 4 to growth. Ammonium sulfate applied at Disease Issues 10 inches in height with 1⁄8 to 1⁄4 inch mesh 1 ounce per gallon of water is typically either on or (as in the case of wood boxes preferred, but urea and other formula- Virus diseases can be spread via any with hardware cloth) attached to the tions may also be used. one of these propagation methods. Be- cause viruses are systemic (distributed bottom. Width and length of propaga- Softwood Cuttings tion beds or boxes vary depending upon throughout entire vascular systems), numbers of cuttings to be rooted. Softwood cuttings are taken before apparently non-symptomatic plant parts Rooting Cuttings. In spring, after flower buds form during the growing sea- of infected plants also contain virus threats of freezing weather have passed, son. The procedures used for hardwood particles (see Chapter 11: Blueberry Dis- insert cuttings vertically 2 to 3 inches cuttings also apply to softwood cutting; eases). Thus, it is critical that propagators apart with one or two buds sticking above however, the latter require more care. use clean, disease-free parent stock for media (Figure 8-1). Distal or basal ends Softwood cuttings should be adequately blueberry cultivation. shaded from sun and properly ventilated

21 Chapter 9

Pruning flower bud and Growth Management vegetative buds

lueberry bushes require annual prun- Bing to help plants become established and to develop vigorous plants that will consistently produce crops of large, early maturing berries. Pruning of established plants is also necessary to manage canes for increased productivity. Canes that are larger than 1-inch diameter at ground level should be removed. These canes use their energy Figure 9-1. Flower buds are plump and located near the terminal end of shoots. Vegetative to produce leaves at the expense of fruit buds are smaller and pointed. production. Large leafy canes also shade inner canopies, resulting in reduced flowering. On the contrary, younger vigorous canes are more efficient at fruit production, and should be preserved. Growers may also selectively prune canes in order to position fruit for ease of harvest. a Pruning is also necessary to remove dead and diseased canes which, if left in the field, can serve as sources for fungal inoculum (see Chapter 11: Blueberry Dis- eases). Many disease-causing pathogens overwinter in dead and diseased canes and should be removed from planting sites and destroyed. Other pathogens, such as the causal agent of stem blight, may be transmitted by tools. Thus, sanitation is an important consideration. When pruning diseased wood, disinfest pruners between cuts or from one plant to the b c next with a commercial sanitizer or with Figure 9-2. (a) Flower buds on first year shoots are large and fruitful. (b) Flower buds on 10 percent solution of Lysol. a third year shoot. Note that the shoot has branched; these flower buds will be fruitful. (c) Shoots that are 5 years and older produce many flower buds on short branched growth at the When to Prune end of shoots. These flower buds produce smaller fruit. Prune plants during dormancy, generally in spring between February and Flowering and Fruiting fruit the following summer. Each flower prior to bud break. Avoid pruning after To prune highbush blueberry plants bud has five to eight flowers, and approxi- bud break because many buds and flow- correctly, it is important to understand mately six of these flowers will produce ers may be rubbed off. Pruning during their flowering and fruiting characteris- fruit. Since 150 to 300 fruit equal one bloom will also retard vegetative growth. tics. It is also important to differentiate pound, 25 to 50 flower buds are needed If possible, prune during dry periods to between fruiting and vegetative buds to produce 1 pound of fruit. The highest reduce the possibility of disease spread. (Figure 9-1). Flower buds are formed quality and largest berries are borne on during late summer and early fall in leaf the most vigorous canes (less than 1 inch axils on top portions of current season’s in diameter at their base) (Figure 9-2). growth. These buds bloom and produce

22 How to Prune At planting, remove from one-third to one-half of the top growth to help balance foliar and root mass. This often improves plant survival. During the first 3 years, leave thicker shoots and remove all spindly wood. The only additional pruning required during this time is removal of diseased or damaged canes. Blossoms should be rubbed off during the first 2 years to promote vegetative and root growth. Blossoms are easily removed by moving a gloved hand quickly along Figure 9-3. Removing an old cane from a Figure 9-4. Removing week, twiggy growth limbs during bloom. If blossoms are left mature blueberry bush. from a mature blueberry bush. on bushes during these early years, plants will produce little growth or become dwarfed, resulting in reduced future eliminate stubs that decay and become Those with erect growth habits often yields. an entry point for disease. Weak, brushy require thinning in plant centers (Figure After the third growing season, or twiggy wood, low limbs, and limbs 9-6). These include: prune bushes into an open-vase shape, extending into the open, vase-shaped Bluecrop Elliot Nelson removing inward-facing branches. Excess canopy should also be removed (Figure Collins Lateblue Reka shoots should be cut at ground level. 9-4). Remove short-branched canes that Duke Legacy Leave the most vigorous, largest diameter are shaded, as these produce fruit that canes intact. ripens late. Flower buds on thick shoots Once blueberry bushes are estab- Mature bushes (more than 3 years (more than 1 inch diameter) tend to open lished, the following pruning method old) have a different set of pruning re- later in spring than those on twiggy wood may be adopted each year: remove two quirements. The first cuts should remove and are less prone to frost injury. of the oldest canes and allow two of the any diseased or injured wood. If two Cultivars with spreading habits newest canes to develop. Altogether, a canes are rubbing against each other, often require pruning of low drooping mature bush should have about 20 pro- remove one of the canes. Next, remove branches (Figure 9-5). Examples of these ductive canes. If a particular cultivar has some (usually about two) of the oldest, cultivars include: small berries, berry size may be increased least vigorous canes so that all canes are Berkeley Chandler Summit by cutting off tips of fruiting wood (tip- less than 5 or 6 years old. When canes Blueray Coville Toro ping). Most growers do not allow plants are removed, cut them as close to the Patriot to grow taller than 6 feet for ease of har- ground as possible (Figure 9-3). This will

Figure. 9-5. Spreading growth habit of Summit blueberry. Figure. 9-6. Upright growth habit of Reka blueberry.

23 vest. If mechanical harvesters are used, growers should maintain a more upright growth habit and a narrower crown that fits the particular harvester. Up to 20 percent of the wood in blueberry bushes may be removed without decreasing yields. Numbers of berries will be decreased, while individual berry size will increase (Figure 9-7). Conversely, if too many blossoms and fruit are left, a large crop of small berries that ripen over a long period of time will result; in fact, many of these small berries may not ripen at all. An ideal blueberry plant has two to three canes of each age up to 6 years old. Overgrown or weak plants may be renewed or rejuvenated by cutting the entire plant to the ground and regrowing a new bush. Sanitation After pruning, all cuttings should be destroyed in order to remove fungal Figure 9-7. Excess flower buds on older shoots may produce fruit that is small and does not inoculum from the planting area. A flail ripen properly. mower may be used to chop cuttings into small pieces so that the prunings break down more quickly. However, if diseases such as Phomopsis canker or Botryo- sphaeria stem blight were problematic during the season, growers should remove all cuttings from the planting site and either burn or bury them as soon as possible (see Chapter 11: Blueberry Diseases).

Figure 9-8. A well-pruned blueberry bush, with canes of varying ages. Older canes have a gray peeling bark, 2- to 4-year canes have a reddish bark with ridges, and young canes have a smooth reddish bark.

24 Chapter 10 Soils, Fertilization, and Nutritional Disorders Figure 10-1. Ideal soils for blueberry pro- Figure 10-2. Raised beds can be an effec- duction are sandy, naturally acidic, and have tive method to improve soil drainage for high organic matter content. successful blueberry production in the lueberry plants have specific soil re- Midwest. Bquirements for optimum growth and production. The best soils for blueberries Most soils also require Table 10-1. Amount of Elemental Sulfur Required To Lower Soil pH for Blueberries (lb/100 sq fta). are well-drained sandy silt loam or silt adjustment of pH. First, soil Target pH of Soil loam, with a pH of 4.5 to 5.2, organic mat- should be tested to deter- Present 4.5 5.0 ter of 4 percent to 7 percent (Figure 10-1), mine current pH and to pH of and adequate phosphorus and potassium Soil Sand Loam Clay Sand Loam Clay determine amounts of sulfur 4.5 0.0 0.0 0.0 0.0 0.0 0.0 (see Chapter 5: Planting and Establish- required to lower soil pH to 5.0 0.4 1.2 1.4 0.0 0.0 0.0 ment). Some areas in the Eastern United optimum levels (4.5 to 5.2 5.5 0.8 2.4 2.6 0.4 1.2 1.4 States contain sandy soils with naturally pH). Refer to the soil testing 6.0 1.2 3.5 3.7 0.8 2.4 2.6 low pH and high organic content. These section of this chapter for 6.5 1.5 4.6 4.8 1.2 3.5 3.7 areas are southwest Michigan, northern more information. 7.0 1.9 5.8 6.0 1.5 4.6 4.8 Indiana, southern New Jersey, and costal Soil acidification is a 7.5 2.3 6.9 7.1 1.9 5.8 6.0 Carolina plains. Blueberries naturally relatively slow process and a To convert to lb/acre, multiply by 435. thrive in sandy soils with high organic can take 6 to 8 months. It Source: Pennsylvania State University, Small Fruit Production and Pest Management Guide. Used with permission. content and high water tables. Thus, these is important to adjust soil regions are major commercial blueberry pH at least 1 to 2 years be- production areas. fore planting, since higher Most Midwestern soils require both amounts of soil acidifying agents may be the treatment and return the pH to its soil amendments and irrigation for opti- applied to bare soil without risk of plant previous level.” mum growth and yield. Soil amendments injuries. A high pH results in reduced Incorporate sulfur, phosphorus, and often include pH adjustments and addi- availability of certain nutrients such as organic matter into the raised beds (up- tion of organic matter. Soil drainage may copper, iron, or manganese. Insufficient per 6 to 12 inches) 3 to 6 months prior to also be required; poorly drained sites may uptake of these mineral nutrients leads to planting. This allows time for chemical require installation of internal drainage yellowing between veins (chlorosis), and reactions to occur and reduces potential systems or surface ditches (see Chapter reduced plant growth and yields. Refer root damage. Retest soil 3 to 6 months 6: Irrigation and Water Management). to the Table 10-1 for information on soil after application and make further ad- In most Midwestern soils that contain acidification or pH adjustment. justments. Apply all nutrients according 10 percent or more clay, raised beds are In locations where top and subsurface to soil test results. Phosphorus will not preferred for improvement of drainage soils have a naturally high pH (6.0 to 8.0) move through soil and is ineffective after (Figure 10-2). Properly prepared raised and there is a high buffering capacity, plant establishment. beds have been shown to be an effective soil amendments may be unable to suf- In rare cases, soils may be too low in way to grow blueberries in mineral soils ficiently lower pH, and blueberries should pH. In this event, manganese or alumi- (a mixture of clay and loam). Preferred not be planted. num can be available at toxic levels. If soil beds are 8 to 10 inches higher than the Sulfur may be used to decrease soil pH needs to be raised, apply lime. original height or soil grade, and 4 feet pH to proper levels if pH is not too high. wide. Over time, beds compact and settle According to the Highbush Blueberry Soil Testing 2 to 4 inches, so addition of hardwood or Production Guide, “as a general rule, It is important to have soil tested a other suitable mulch will be necessary modification of soil with 20 percent or year or two before planting. If soil pH is to maintain bed height (see Chapter 5: more of its exchangeable capacity satu- too high, soil pH-reducing agents, such Planting and Establishment). rated with calcium or with 2,000 pounds as elemental sulfur or iron sulfate, should of calcium per acre is impractical. Modi- be applied to reduce soil pH. Soil tests fying such soils is expensive and does not reveal buffer pH (also called lime index), last; the underlying soil tends to buffer nutrient levels, and base saturation. A

25 fertilizer recommendation will also be Table 10-2. Interpretive Nutrient Levels For Tissue Analysis of Blueberries provided with test results. % Dry Weight Low Normal High Excessive Soil samples should be collected with Nitrogen 1.65 1.70 2.10 2.50 a soil tube or probe (Figure 10-3), when- Phosphorus 0.06 0.07 0.18 0.22 ever possible, to ensure that all samples Potassium 0.35 0.40 0.65 0.80 are taken at the same depth. Though not Calcium 0.25 0.30 0.80 1.00 as accurate, a shovel or garden trowel Magnesium 0.18 0.20 0.30 0.40 may be used. Sampling depth for blue- Sulfur 0.06 0.12 0.20 0.80 berries is 8 inches. Remove sod, mulch, ppm Dry Weight or organic debris first. Take 12 to 15 Manganese 45 50 500 650 soil cores or samplings randomly from Iron 65 70 300 400 an entire area. Soil cores should be air Copper 4 5 15 20 Figure 10-3. Soil testing should dried, crumbled, and mixed together to Boron 29 30 50 65 be done using a soil probe or a Zinc 9 15 30 40 form a composite sample. A composite shovel a year or two before blue- soil sample should represent a field of 5 berry bushes are planted. Source: Penn State University Agricultural Analytical Ser- vices Lab acres or less. Separate soil samples should be taken for different cultivars (or types) or fields containing different soil types, topography, or fruit yield. A “standard” Tissue Testing Typical values used to interpret tissue test should be requested. In addition, Tissue samples are the best way to nutrient levels are provided in Table 10-2. organic matter content test and a particle monitor the nutrient status of blueberry Each tissue test report should indicate size analysis should also be performed for plants. Soil sampling is only an estimate mineral nutrient presence, ranging from a greater evaluation of the soil condition. of nutrients available in soils, but tissue low to excessive. Different labs employ There are many university and private sampling measures the nutrient concen- different ways to report data, but each soil and tissue testing labs available. Con- trations in plants. One tissue sample can should provide recommendations to sult local Extension offices for soil testing represent up to 5 to 10 acres of blueber- correct nutrient disorders. labs. Some universities, such as University ries. However, multiple samples provide Fertilization of Kentucky, Michigan State University greater accuracy. and Pennsylvania State University, still Because the suggested sampling Fertilize blueberry bushes according operate soil testing labs. Other universi- time recommendations may differ from to soil and tissue test reports. Soil tests ties, such as Purdue University and The one lab to another, consult with local reveal nutrients available in soils, while Ohio State University, no longer have Extension agents for more information. tissue tests reveal amounts of nutrients such labs and direct growers to private For example, Michigan State University taken up by plants. It is important to sources. recommends tissue sampling in between utilize both tests to determine amounts Instructions on soil or tissue sampling July 15 to August 15, while Penn State of nutrients needed by blueberry bushes, techniques are also available from indi- University recommends the first week of especially for established plantings. vidual soil or tissue testing labs. Growers fruit harvest. Check with the testing lab Blueberry plants, like all plants, require are encouraged to check the website(s) you work with for optimum timing and 17 essential elements. Three of these of soil and tissue testing labs for proper sampling techniques. are essential non-mineral elements that sampling techniques. Good samples are Tissue samples should consist of are taken up from atmospheric carbon the first critical step in ensuing accurate leaves taken from middles of current dioxide and water: carbon (C), hydrogen results. year’s growth. Collect 100 fully expanded (H), and oxygen (O). Selection of a reputable testing lab is leaves per sample. Avoid leaves that are The other fourteen elements are also important. It is beneficial to utilize damaged, as well as those that are near essential minerals: nitrogen (N), phos- the same lab year after year for consis- fruit clusters or on vigorous first-year phorus (P), potassium K), calcium (Ca), tency, since extraction methods and shoots. Sample leaves from as many dif- magnesium (Mg), sulfur (S), boron (B), recommendations can very significantly ferent bushes as possible to get a repre- copper (Cu), iron (Fe), chloride (Cl), from one lab to the next. Growers can sentative sampling of the entire planting. manganese (Mn), molybdenum (Mo), have the soil tests performed through soil Wash leaves to remove dust and spray zinc (Zn), and nickel (Ni). The elements testing labs affiliated with local Extension residue, blot them dry with a clean paper N, P K, Ca, Mg, and S are considered offices or universities, or they may work towel, and allow them to air dry in a well- macronutrients and are needed in large directly with a commercial soil and tissue ventilated location 1 to 2 days. Ship dried quantities. B, Cu, Fe, Cl, Mn, Mo, Zn, and testing lab. leaves in paper bags. Tissue sample forms Ni are considered micronutrients and are should be downloaded from the testing needed in smaller quantities. Since some lab’s website, filled out, and included with mineral elements are present in sufficient the tissue sample. quantities in soils, they may not need to be applied through fertilization.

26 Figure 10-4. A fertilizer injector can be used Figure 10-5. Nitrogen deficiency in blueberry is usually characterized by a light green to yel- to inject water soluble fertilizer through drip low color on older leaves, along with poor growth. irrigation.

Blueberry plants are sensitive to blueberry plants. Ammonium sulfate is readily soluble fertilizers and excessive recommended when soil pH is above 5.0, amounts can cause plant injury or death. and urea is best for soils below 5.0. Apply Therefore, it is critical to apply fertilizer at urea during cool, rainy weather or irrigate recommended rates. Broadcast elements after application. Ammonium sulfate or evenly; do not concentrate fertilizer in a urea may be injected through drip (aka. small area, such as in centers of plants or trickle or micro-irrigation) systems (Fig- against canes. ure 10-4). Use one half of recommended Nitrogen Application. Annual appli- ground application rates when applying cations of nitrogen (N) are necessary N with irrigation or in banded applica- for vigorous growth and development. tion. Blueberry plants prefer the ammonium Nitrogen rates differ depending upon Figure 10-6. Magnesium deficiency usually form of N rather than nitrate. Do not plant age. For newly planted blueberries, shows up as a green “Christmas tree” in the apply nitrate formulations to blueberries; broadcast two applications each of 10 center of a chlorotic leaf. it is too readily soluble and can injure pounds of actual N per acre—once at

a b Figure 10-7. (a) Iron deficiency occurs on younger leaves and (b) is characterized by yellowing between veins.

27 bloom and again 3 weeks later. Young leaves with color that is uniform across this iron may be in an unavailable form. plants require approximately 10 pounds leaves and with no particular pattern Soil pH above 5.3 causes low iron avail- of actual N per acre at each broadcast (Figure 10-5). Both leaf veins and tissue ability. In addition, high calcium or phos- application in mid-April, mid-May, and between veins are light yellow. Light phorus can induce iron chlorosis. During mid-June during years two to four. In green color appears on older leaves first dry summer months, blueberry bushes mature plantings, 50 to 70 pounds of because nitrogen is mobile in plants. may exhibit temporary iron deficiency, actual N is often needed, but growers Nitrogen deficient blueberry bushes are especially if they are irrigated with alkaline should respond to tissue sample results often smaller in size than healthy plants. water from deep wells in lime rock. and maintain leaf nitrogen levels be- They also have shorter stems, fewer new To correct iron chlorosis, soil pH tween 1.7 percent and 2.1 percent, and canes, and lower yield. Sometimes, small should be reduced with applications of potassium levels between 0.35 percent brown or red spots may appear on light elemental sulfur or iron sulfate to the root and 0.40 percent. Refer to Table 10-2 for green-colored leaves. zone. Iron chelate can be applied as a foliar nutrient levels of mineral nutrients. Phosphorus Deficiency. Phosphorus is spray, although results are temporary. Fol- When injecting nitrogen fertilizer an important element for root growth low directions on product labels, as there with drip (trickle) irrigation, broadcast and energy transfer within plants. Phos- are many forms of iron chelates. A surfac- the mid-April application as recom- phorus deficiency is not common in tant should also be used to help move iron mended and then apply one-half of blueberries. However, when it occurs, chelate into waxy blueberry leaves. the remaining broadcast amount from phosphorus deficient leaves show purple Manganese and Copper Deficiencies. mid-May to mid-June through drip ir- coloration in older leaves. This is be- The deficiencies of manganese and cop- rigation. (Example: 60 pounds annually cause phosphorus is involved in the per can be common. Symptoms mimic = 30 pounds mid-April, broadcast; 30 translocation of sugar or carbohydrates. those of iron deficiency. Only tissue pounds irrigated mid-May to mid-June). Insufficient phosphorus results in sugar tests can reveal levels of manganese and Monitor leaf nutrient levels to make sure accumulation, and excessive sugar ac- copper. Do not apply a combination of that blueberry plants receive adequate cumulation leads to red pigment pro- copper, iron, and manganese to plants be- supplies of minerals for optimum growth duction. Phosphorus deficient blueberry cause they may have antagonistic effects and production. bushes are also smaller in size. on each other. Foliar spray of copper or Continue to irrigate with water only Potassium Deficiency. Potassium con- manganese should be applied separately after mid-June, as needed. In most Mid- tributes to photosynthesis and water to determine which is responsible for western areas, soil may lose 0.25 to 0.30 regulation. Potassium deficiency is also deficiency symptoms. inches of water per day. Use a tensiometer rare in blueberries in the Midwest. to monitor soil moisture, if possible, Typical symptoms are browning of leaf Additional Resources maintaining 20 to 25 centibars in the margins or marginal scorching of older Ellis, M., M. Brown, B. Bordelon, D. Doo- upper 12 inches of soil. leaves. han, R. Funt, R. Williams, and C. Welty. Calcium Deficiency. Blueberries have a 2004. Ohio State University Extension Mineral Nutrient Disorders low requirement for calcium and seldom, Bulletin No. 861, Midwest Small Fruit Nutrient disorders are the symptoms if ever, are deficient. Pest Management Handbook, The that plants exhibit when too little of an Magnesium Deficiency. Magnesium Ohio State University, Columbus, Ohio. essential nutrient (deficiency) or too is involved in chlorophyll production. Hart, J., B. Strik, L. White, and W. Yang. much of an essential nutrient (toxicity) is Magnesium deficiency is not common 2006. Nutrient Management for Blue- absorbed by growing plants. It is beyond in blueberries. On highbush blueberries, berries in Oregon. EM-8918. Oregon the scope of this bulletin to discuss all magnesium deficiency is characterized State University, Corvallis, OR. of the possible mineral deficiencies and by a green area in the shape of a Christ- Ohio State University Extension Fact toxicities. Growers are encouraged to refer mas tree in centers of chlorotic leaves Sheet. HYG No. 1132-09. Soil Testing to additional literature on plant nutrition, (Figure 10-6). Since magnesium is mobile Is an Excellent Investment for Garden, mineral nutrient deficiencies, and toxici- in plants, deficiency symptoms usually Lawn, and Landscape Plants, and ties, or to contact local Extension agents occur on older leaves. Commercial Crops http://ohioline. or specialists for assistance. Common Iron Deficiency. Iron is involved in osu.edu/hyg-fact/1000/pdf/1132.pdf. nutrient deficiencies in blueberries are chlorophyll production. Iron deficiency Pritts, Marvin, P. and J.F. Hancock (edi- discussed below. usually occurs on younger leaves first tors). 1992. Highbush Blueberry Pro- Nitrogen Deficiency. Nitrogen is es- (Figure 10-7a) since iron is not mobile duction Guide, NRAES-55. Northeast sential for the synthesis of protein and in plants. Iron deficiency, also referred Regional Agricultural Engineering chlorophyll. Nitrogen deficiencies are to as iron chlorosis, is characterized by Service, 152 Riley-Robb Hall, Coop- common in blueberries. Typical symp- yellowing between veins (Figure 10-7b). erative Extension, Ithaca, NY 14853. toms are characterized by light green Blueberry bushes deficient in iron may Phone: (607) 255-7654. show adequate levels of iron in soils, but

28 Chapter 11 Blueberry Table 11-1. Disease Resistance in Blueberry Cultivars Commonly Grown in the Midwest. Diseases

Cultivar Mummy Berry Phomopsis and Blight Twig Canker Powdery Mildew Anthracnose Rot Fruit Red Ringspot Virus Shoestring Virus Botryosphaeria dothidea Arlen R lueberry is considered one of the most Berkeley S VS R - VS - Bdisease-free fruit crops in the Midwest. Bluecrop MR - MR VS MR VR Many of the diseases that do affect blue- Bluegold S - - MR - - berry result in minor damage; however, Bluehaven SS---- a few can impact plant health and yields. Bluejay R - - MR - R Blueray S - - VS S - The keys to avoiding most blueberry dis- Bluetta S R - VS - - ease problems are proper site selection Bounty VS and following good crop management Brigitta Blue R practices. Development and use of an Burlington R----S integrated disease management program Cape Fear R (similar to an IPM program) is essential to Chanticleer VS the successful production of blueberries. Collins S----- Coville MR - MR VS - - Integrated Management Darrow R----R of Blueberry Diseases Duke MR - - - - S The objective of an integrated disease- Earliblue S S MR - - S Elliott MR R R R - S management program is to provide a Hannah’s Choice MR MR commercially acceptable level of disease Harrison S VS control on a consistent (year-to-year) ba- Jersey MR VS S VS/MR MR S sis. This is accomplished by development Lateblue R----- of a program that integrates all available Legacy MR R control methods into one program. An Little Giant ---R-- effective disease-management program Morrow R for blueberries must emphasize the inte- Murphy S R R grated use of specific cultural practices, Northblue R----- knowledge of pathogen and disease biol- Northland S----R ogy, disease-resistant cultivars, and timely Northsky R----- O’Neal R applications of approved fungicides or Ozark Blue R biological control agents, when needed. Pamlico R In order to reduce the use of fungicides Patriot MR - - - - - to an absolute minimum, use of disease- Polaris ------resistant cultivars and various cultural Rancocas MS - R - - MS practices must be strongly emphasized. Reka MR MR Blueberry cultivars with high levels of Reveille R MR resistance to most of the major diseases Rubel S MR - MS - S are not currently available; however, sev- Sierra S - - MR - - eral cultivars are known to be resistant Spartan MR - - VS - S to multiple diseases. Table 11-1 provides Star R information on disease resistance in Toro MR - - MR - - Weymouth S - - - - S several of the most common blueberry VR = very resistant, R = resistant, MR = moderately resistant, MS = moderately susceptible, S = suscep- cultivars grown in the Midwest. tible, VS = very susceptible; - = resistance is not known. Table based on information provided by J. Hancock, E. Hanson, D. Trinka, and A.M.C. Schilder, Michigan Cultural Practices for Disease State University. Control in Blueberry The use of any practice that provides and implemented in disease manage- nursery. Remember that disease-free an environment within the planting that ment programs. plants are not necessarily disease re- is less conducive to disease development Use Disease-Free Planting Stock. Always sistant—cultivar selection determines and spread should be used. The practices establish plantings with healthy, virus- disease resistance. listed here should be carefully considered indexed plants obtained from a reputable

29 Select Sites Carefully. Selecting a ducing the amount of fungal inoculum. • Market berries as quickly as possible. planting site with good water drainage For example, removal of fruit mummies Encourage customers to handle, re- is extremely important; avoid low, poorly is critical for mummy berry control, frigerate, and consume or process fruit drained wet areas. When there is stand- while the removal of infected twigs and immediately. Remember that even ing water in the field, plants are subject to branches is important for controlling under ideal conditions, blueberries infection. Any site in which water tends Phomopsis twig blight and other canker- are quite perishable. to remain standing after rains is, at best, causing diseases. only marginally suited for blueberry Avoid Excessive Fertilization. Fertility Use of Fungicides production and should be avoided. should be based on soil and foliar analy- Although fungicides are an important Effective water drainage (both surface sis. Excess fertilizer, especially nitrogen, component of the integrated disease and internal drainage) is especially im- should be avoided. Sufficient fertility is management program in the larger blue- portant for control of Phytophthora root essential for producing a crop, but exces- berry production regions, such as Michi- rot. This water-mold pathogen requires sive nitrogen can result in dense foliage gan, fungicides are not extensively used free water (saturated soil) in order to that increases drying time in the plant in most Midwestern blueberry plantings. infect plants and establish in root zones. canopy (i.e., remains wet). This is one of the reasons that blueber- If there are low areas in fields that have Maintain Proper Soil Conditions. Vigor- ries are considered to be one of the most tendencies to remain wet, Phytophthora ous plants are not as susceptible to infec- disease-free fruit crops in the Midwest. root rot will often develop. tion by pathogens. If infection does occur, However, if certain diseases become Any practice (such as tiling, ditching, disease often does not reach epidemic established, fungicides may be required or planting on ridges or raised beds) that proportions. to help manage disease. A good approach aids in removing excessive water from Protect from Winter Injury. Winter to blueberry disease control is use disease root zones is beneficial to the disease injury predisposes blueberry plants to resistant (or at least, less susceptible) management program. many diseases. In colder regions of the cultivars combined with good cultural Site Exposure. A site with good air Midwest, snow can be piled around practices. Therefore fungicides will be circulation that is fully exposed to direct bushes to insulate from fluctuating tem- used only in plantings where potentially sunlight should be selected. Avoid shaded peratures. Protect crowns (base of plant damaging disease develops. areas. Good air movement and sunlight at soil line) with wood-chip or straw For the most current information on exposure are important to aid in drying mulch. Injury sites are often ideal infec- fungicides registered and recommended fruit and foliage after rain, irrigation, tion or entry sites for pathogens. for control of blueberry diseases, obtain morning dew, or fog. Any practice that a copy of the “Midwest Small Fruit and promotes faster drying of fruit or foliage Harvesting Procedures Grape Spray Guide” through your local will aid in the control of many different • Pick fruit frequently and early in the cooperative Extension agent or educator. diseases. day before the heat of the afternoon This publication is also available on the Control Weeds. Weed control is essen- (preferably as soon as plants are dry). Internet. tial to successful blueberry production. • Overripe berries are most susceptible From the disease control standpoint, to fruit rot pathogens, and can develop Major Root and Stem Diseases weeds in plantings prevent air circulation symptoms during and after harvest. It is important for growers to be able to and result in fruit and foliage staying wet • Handle berries with care during recognize the major blueberry diseases. for longer periods. Several diseases can be harvest to avoid bruising. Bruised Proper disease identification is critical more severe in plantings with poor weed and damaged berries are extremely to making the correct disease manage- control compared to plantings with good susceptible to many rot diseases. ment decisions. In addition, growers weed control. • Train pickers to recognize and avoid should develop a basic understanding of Some weeds can serve as hosts for berries that have disease symptoms pathogen biology and disease cycles for plant pathogens such as fungi, viruses, such as mummy berry or anthracnose. the major blueberry diseases. The more and nematodes. Removal of weeds re- If possible, have pickers put these ber- growers know about diseases, the better duces inoculum. ries in a separate container and remove equipped they can be to make sound and In addition, weeds will reduce produc- them from the field. effective management decisions. tion through direct competition with The following is a description of blueberry plants for light, nutrients, and Post-Harvest Handling symptoms, causal organisms, and man- moisture. Weeds will make the planting • Always handle fruit with care during agement options for the most common less attractive to pick-your-own custom- movement from field to market to blueberry diseases in the Midwest. ers, especially if there are thistles! avoid any form of damage. For additional sources of information, Practice Good Sanitation. Any practice • Get the berries out of the sun as soon consult the resources at the end of this that removes and destroys infected as possible. chapter or contact local Extension agents twigs, branches, and other plant debris • Refrigerate berries immediately to or specialists. present in plantings is beneficial in re- 32°F to 35°F in order to slow the development of fruit rots.

30 Phytophthora root rot, caused by the Figure 11-1. Premature foliar discoloration due to Phy- tophthora root rot. water mold (oomycete) Phytophthora cinnamomi, causes root decay in warm, Phytophthora root rot wet soils. Highbush blueberries, which Disease Management are intolerant of poorly drained soils, Site selection is critical. Avoid poorly or marginally are extremely susceptible. The soil-borne drained soils. Improve drainage by planting on raised beds or install pathogen attacks small feeder roots, drainage systems prior to planting. spreads to main roots, and eventually in- Avoid excess irrigation. vades crowns. Above-ground symptoms Fungicides such as mefenoxam and phosphorus acid are begin with leaves yellowing or reddening effective in controlling diseases caused by Phytophthora (Figure 11-1). Lack of water and nutrient spp. and other water molds. uptake (caused by root loss) eventually leads to stunting, lack of new growth, and Figure 11-2. (a) Small, red lesions plant death. due to Botryosphaeria (b) develop This fungus-like pathogen is com- into cankers. monly present in soil; however, under op- Botryosphaeria stem canker timal conditions, it can infect and destroy Disease Management blueberry plantings. Water molds such as Use clean, disease-free planting Phytophthora spp. require free water to stock. survive and reproduce. Spores have long Remove and destroy infected stems, whip-like structures (flagella) that assist cutting at least 6 inches below each in their “swimming” movement. Wet lesion. Fungicides are ineffective once soils provide a medium for pathogens to infection occurs. Preventative move into root zones. Once established, fungicides may be used in high-risk these pathogens produce overwintering a b plantings. structures (chlamydospores) that can survive in a variety of climate extremes. When environmental conditions reach optimal levels (68° to 90°F), accompanied by saturated soils, the pathogen breaks out of dormancy and infects susceptible plants. Botryosphaeria stem canker, caused by the fungus Botryosphaeria corticus, is an important disease of highbush blueberry in the Southeast and may become an important disease in the a b more southern regions of the Midwest. Figure 11-3. (a) Botryosphaeria dieback symptoms. (b) Brown discoloration under the bark of The first symptoms appear as small red cane infected with Botryosphaeria stem blight. lesions on succulent stems (Figure 11-2a), which often resemble winter injury on Botryosphaeria stem blight new wood. These lesions develop into Botryosphaeria stem blight (or die- Disease Management cankers (Figure 11-2b). The fungus can back), is caused by the fungus Botryo- sphaeria dothidea. Symptoms include Avoid wounding plants. only infect the current season’s growth; Retain vigorous plants by promoting opti- however, the disease can progress into yellowing, reddening, or drying of leaves mum health. older tissues. on one or more branches (Figure 11-3a). Avoid fertilizing late in the growing season Optimal conditions for spore produc- As symptoms progress in infected stems, (August or later). Plants fertilized late in the tion and infection are temperatures be- leaves turn brown and remain attached season do not harden off properly (winter- for a period of time. Brown or tan lesions ize) and are more susceptible to winter tween 77° and 82°F and wet conditions. injury. Winter-injured tissues are most Upon infection, the pathogen grows develop on stems. Upon cross-sectioning susceptible to infection. slowly and does not seriously affect plants infected stems, internal wood appears If stems become infected, remove infected the first year. Without proper disease brown on the diseased side of the stem tissue at least 6 inches below each lesion. management, disease becomes increas- (Figure 11-3b). Blighted young plants Fungicides are ineffective against Botryos- can die within 2 years. Symptoms often phaeria stem blight. ingly more severe each year. Resistant cultivars include: Murphy, Cape resemble winter injury. Young plants Fear, O’Neal are more susceptible than older, well- The disease has been observed primarily on established plants. the cultivar Duke.

31 Infections occur in spring (May-June) Figure 11-4. Phomopsis twig blight causing (a) when temperatures reach 82° to 88°F. loss of flower buds and (b) death of branches. The pathogen enters host tissue primar- Phomopsis twig blight or stem canker ily through wounds, such as mechanical Disease Management damage or Phomopsis infections. In- Remove infected twigs during dormancy and fected stems may provide overwintering blighted twigs that develop during the growing season by cutting at least 6” below infected tissue. sites for the fungus. Disease susceptibility Avoid overhead irrigation to reduce amounts of decreases as plants age. a splashing spores. Phomopsis twig blight or stem canker, Avoid planting sites that are prone to spring frosts caused by Phomopsis vaccinii, is the most and use fertilizer, irrigation, and weed control common canker disease in blueberry and practices that discourage late season growth and that promote early hardening off in winter. is one of the first diseases to develop in A protectant fungicide such as captan, azoxys- spring. Symptoms include dead or blight- trobin, fenbuconazole, or propiconazole may ed 1-year-old twigs that eventually cause be applied at bud-break and at regular intervals loss of flower buds (Figure 11-4a). Early through full bloom in plantings with high risk for symptoms occur shortly after green-tip, infection. A dormant application of lime sulfur during bud at which time buds begin to turn brown break is recommended in plantings where disease and die. Necrotic, reddish-brown lesions is established. often develop around these blighted buds Avoid stem wounding to reduce amounts of infec- and then spread downward. Eventually tion through canes. stems die, and sudden wilting and flag- Avoid overripe fruit. ging of stems occur as warm summer Resistant cultivars include: Bluetta, Elliott weather progresses. Leaves on infected b Susceptible cultivars include: Murphy, Harrison twigs often turn reddish and remain attached to stems. Girdling cankers can Figure 11-5. Crown gall. kill entire twigs (Figure 11-4b), while leaf spots may occur on foliage of surviving Crown gall twigs. Late-season symptoms can also Disease Management include premature ripening of fruit or Use clean stock that is free from the pathogen. If infection occurs, remove and destroy diseased fruit rot. plants. Infection by this fungus occurs Rotate away from susceptible plants for 3 years if through opening buds. In flower buds, soil becomes infested. pathogens move through blossoms and into vascular tissue of stems, killing multiple unopened flower buds. The fungus can also penetrate fruit directly. During red or reddish-brown and somewhat the second year, twigs become blighted puckered (Figure 11-6). White powdery and bud loss is more severe. The fungus fungal growth may develop on upper overwinters in dead or infected twigs. leaf surfaces during humid weather and During spring, spores ooze from stem le- occasionally on lower leaf surfaces on sions at precisely the same time as bloom. This disease is caused by a soil- some cultivars. Plants may defoliate dur- Rain splashes spores onto flowers. These borne bacterium that enters plant tissue ing severe infections. For the most part, spores can also infect through wounds through natural and mechanical wounds powdery mildew is a superficial disease; on young woody stems, causing cankers. on stems and roots. It is more prevalent the fungus only penetrates leaf surfaces Infection through stems is most common in neutral to alkaline soils. (epidermis). This is a summer disease that on those damaged or wounded by freeze. Foliar Diseases is more severe in warm, dry climates. Crown gall, caused by the bacterium Powdery mildew, caused by Micros- The powdery mildew fungus over- Agrobacterium tumefaciens, is usually phaera vaccinii, is commonly associated winters in fallen leaves or on dormant not a severe problem in blueberry. It most with lowbush blueberry, but is rarely a buds as fruiting bodies (cleistothecia). often occurs in propagation beds and problem on highbush blueberry. Damage Spores (ascospores) within these fruiting new plantings, but not mature plantings. from the pathogen is usually not seri- structures are released and initiate infec- Symptoms include stunting of plants and ous, but can sometimes become severe. tions during warm, humid weather. Free development of galls at bases of canes Disease symptoms begin as light green water, such as rainfall, impedes (stops) (Figure 11-5). Galls eventually turn dark or yellow areas on leaves in midsummer. sporulation and infection. Once pri- brown and rough, and harden with age. Infected leaf tissue develops spots with mary infections occur, airborne spores red halos and then becomes entirely (conidia) are produced which continue

32 the infection cycle. During autumn, the Figure 11-6. Powdery mildew. overwintering structures appear as dark Powdery mildew specks on infected leaves. Disease Management Fungal leaf spots are generally consid- Fungicides are usually not required. ered minor diseases of highbush blueber- Space and prune plants for maxi- ries in the Midwest. They may be caused mum air circulation and reduced by a variety of fungi: double spot by Do- humidity. thichiza caroliniana, Gloeosporium leaf spot and dieback by Gloeosporium minus (Figure 11-7), Gloeocercospora leaf spot by Gloecercospora inconspicua, Phomopsis leaf spot by Phomopsis vaccinii (Figure 11- 8), and Phyllosticta leaf spot (Figure 11-16) by Phyllosticta vaccinii and P. elongate. Symptoms range from small brown Figure 11-7. Fungal leaf spots leaf spots with reddish or purplish mar- Gloeosporium leaf Disease Management gins to larger irregular lesions. Fungal spot. When possible, avoid planting susceptible cul- fruiting bodies may appear as dark specks tivars, such as: Jersey (Gloeosporium, Phyllostic- in spots. Spots may develop during mid- ta), Murphy (Phyllosticta), Harrison (Phyllosticta) to late-summer, a few weeks after periods Limit overhead irrigation. of frequent rainfall. In severe cases, defo- Space and prune bushes to reduce humidity liation may occur. Fungi that cause leaf and promote rapid leaf drying. Fungicides may be applied after harvest and spots may also infect and kill succulent through leaf drop to control subsequent infec- stems, causing severe dieback. tions. Leaf spot fungi overwinter in infected Maintain a clean planting floor; rake or culti- tissue that falls to field floors. Rain dis- vate (bury) fallen diseased leaves. perses spores as temperatures warm. Infection occurs during mid-season, but symptoms are not visible until mid- to late- season, or 1 month after infection. Leaf rust, caused by Nachidemyces vaccinii, formerly referred to as Pucci- niastrum vaccinii, is a minor disease of Figure 11-8. Phomopsis leaf spot. highbush blueberry, but it sporadically causes epidemics on lowbush blueberry in the eastern United States. Symptoms begin as yellow leaf spots during early summer, developing into reddish leaf lesions in mid-season (Figure 11-9a). Orange sporulating pustules develop on undersides of leaves (Figure 11-9b). Infected leaves, which rapidly turn yellow and then brown, fall prematurely from bushes. Infection occurs during late spring when spores (aeciospores) are blown a b from hemlock. Hemlock is the alternate Figure 11-9. (a) Symptoms of leaf rust on upper leaf surface, and (b) pustules on host and is required for the disease to the leaf underside. complete its cycle. Infected blueberry produces a “repeating” spore type (ure- on blueberry leaves and initiate infection Leaf rust diniospores) in midsummer, which can (basidiospores) on hemlock in spring. The Disease Management reinfect and continue to spread disease cycle continues as the fungus sporulates Remove hemlock within one-third of a mile on blueberry. A different spore type of orchards. during late spring and infects blueberry Avoid planting susceptible cultivars, such as: (teliospore) is produced on blueberry again. If hemlock is not in the area, pri- Corville, Pemberton, Washington, Atlantic during late-fall. Teliospores overwinter mary spring infections are not likely. No fungicides are registered for this disease.

33 Septoria leaf spot and stem canker, Figure 11-10. Septoria leaf spot. caused by Septoria albopunctata, is a Septoria leaf spot and stem canker fungal disease of highbush and rabbiteye Disease Management blueberries. Symptoms include tan spots Rake or cultivate (bury) fallen diseased leaves. with reddish-purple halos that develop Apply 4 applications of fungicides such as captan and thiophan- during spring (Figure 11-10). Often, dark ate-methyl beginning after harvest and continue until leaf drop. spore-producing structures (pycnidia) Susceptible cultivars include: Murphy, Bounty develop in centers of leaf spots on upper leaf surfaces. If stems become infected, lesions appear purple with centers which Figure 11-11. Red leaf. eventually become tan or lighter in color. Pycnidial structures develop in centers Red leaf of stem cankers, as well. This disease is Disease Management most severe in cuttings and young plants. Remove and destroy infected plants; plants will not recover from Septoria leaf spot symptoms are similar to this disease. Healthy bushes that are near infected plants may be treated with Botryosphaeria and Phomopsis leaf spots. a protectant fungicide when white fungal growth (hymenium) The fungus overwinters in infected develops on leaves of nearby infected plants. Maintain a regular leaves that have fallen to the ground or protectant spray schedule as long as the fungus produces spores remain attached to stems through winter (basidiospores) on leaves. and in stem lesions. Sporulation begins Avoid excessive nitrogen fertilization. during rainy periods as weather warms ° ° (75 to 80 F). Symptom development Fruit and Flower Diseases Alternaria fruit rot, caused by Alternar- increases progressively through summer. Red leaf, Overall, management for fruit and ia tenuissima, is the most common fruit caused by the fungus Exoba- rot of highbush blueberry. Symptoms sidium vaccinii, is a disease of blueberries flower diseases includes some basic cultural practices, below. Additional begin as sunken lesions at the calyx end of in the northwestern United States. It fruit. Lesions later turn gray-green with is most commonly found on lowbush recommendations are listed with each specific disease. fungal masses (mycelia) and dark green varieties, but it may occasionally occur spores (conidia) (Figure 11-12). Infected on highbush. Symptoms include red- • Plant resistant cultivars. • Reduce nitrogen in spring to limit suc- fruit become leaky. Fruit may not develop dening, thickening, and puckering of symptoms until after harvest; this disease terminal leaves in mid-summer (Figure culent growth. Do not apply nitrogen late in the growing season (August is most severe as a post-harvest rot. Leaf 11-11). During late summer, a white layer infections, which appear as small, round, of fungal spores develops underneath or later). • Reduce humidity with spacing and necrotic spots with red halos, can occur infected leaves; these leaves then become as temperatures warm above 70°F. necrotic. Infected plants do not flower. pruning. • Follow spray recommendations if The fungus is a common saprophyte Symptoms do not appear the same year and overwinters in dried-up berries as infection, and second-year symptoms plantings have a history of disease. • Remove infected tissue. (mummies) and leaf debris, or on dead are minimal. In fact, it may be several peduncles as mycelia and spores. During years before symptoms are noticeable. • Harvest berries often to avoid overripe fruit. cool wet weather, usually between late Once the fungus becomes established, bloom and fruit maturity, spore produc- symptoms appear on new growth every • Promptly cool harvested berries. year. During the advanced stages of disease, new leaves are red upon emergence. Figure 11-12. Alternaria fruit rot. Plants die after several years. Alternaria fruit rot Infection by this fungus is systemic Disease Management (inside plant tissue, dispersed through- Cultivars with dry stem scars, such out) and cannot be cured. Fungal spores as Bluehaven, are less prone to develop on leaf lesions in spring and infection. summer and are blown by wind. Opti- If disease is a problem, a regular spray program from early bloom mal fungal conditions are cool, moist until harvest may be beneficial. environments and excessive nitrogen. Pick fruit frequently as it ripens. Do not allow fruit to become overripe. Fruit should be rapidly cooled after harvest to inhibit symptom development.

34 tion occurs. Rain and wind disperse Figure 11-13. Fluffy fungal masses develop on Botrytis-infected fruit. spores. Leaf spots can occur early in the growing season and fungal sporulation can occur throughout the season. Infec- Botrytis fruit rot and blossom blight tion from these late-produced spores Disease Management can infect stem scars, resulting in post- Cultivars with loose clusters pose less risk for disease outbreaks. harvest rot. This fungus grows most Space plants, and prune for increased profusely at temperatures from 65° to circulation and rapid drying of tissue. 70°F and high humidity. Avoid excess nitrogen, which can Botrytis fruit rot and blossom blight, stimulate growth and produce suscep- caused by Botrytis cinerea, is usually a tible, tender tissue. Pick fruit frequently as it ripens. Do not minor disease of highbush blueberry, but allow fruit to become overripe. it can be a major problem on lowbush Fruit should be rapidly cooled after blueberry. Fast-growing, gray/tan, fluffy harvest to inhibit symptom develop- fungal masses (mycelia) and spores (co- ment. nidia) develop on infected fruit (Figure 11-13). This disease may appear similar to Alternaria fruit rot; however the with 6 to 9 days of humid or wet weather. 11-14b), veins of leaves, and at bases of fungal growth of Botrytis is not dense Sporulation can occur any time of year flowers. Young vegetative shoots gener- or as green as that of Alternaria. Tender during periods of a few hours of ideal ally die and fall to the ground within 72 growth such as blossoms, fruit, and temperatures and free water. Spores are hours. Symptoms may disappear until young leaves are most susceptible to in- spread by wind and rain. berries begin to ripen. At this stage, ber- fection. Infection of blossoms causes the Mummy berry, caused by the fungus ries that develop from infected flowers most severe damage, as infected blooms Monilinia vaccinii-corymbosi, is one of begin to rot. They soon turn pink or gray do not develop fruit. Occasionally, green the most serious and most economically (Figure 11-14c) and shrivel and harden twigs may become infected; damage important diseases of blueberry fruit. All into mummies (Figure 11-14d). may resemble winter injury. Mature blueberry varieties are susceptible, espe- The fungus overwinters in hard, dry hardened plant parts are rarely affected. cially highbush types. Early symptoms berries or mummies (pseudosclerotia) Botrytis fruit rot occurs after harvest. include rapid blighting of twigs (Figure that fall to the ground. These structures The fungus overwinters as either vi- 11-14a) and shoots, followed by produc- may survive for several years. In spring, able masses of fungal tissue (mycelia) or tion of fungal spores within a 24-hour pe- when conditions are rainy and as tem- hardened survival structures (sclerotia) riod. These spores (conidia) form dense, peratures reach 50° to 60°F, the fungus in plant debris, fruit, stems, and leaves. tan-gray tufts. Infected young leaves and forms fruiting bodies (apothecia) (Figure Sporulation occurs in spring as tem- shoots often wilt; leaves frequently de- 11-14e) that produce spores. These spores peratures range between 59° and 68°F velop brown areas along midribs (Figure (ascospores) are carried by wind and rain

Mummy berry Disease Management Practice strict sanitation; cultivate or remove mummies from orchards to eliminate the primary source of inoculum (ascospores) in spring. Prune wounded canes and plant parts damaged by frost, as they are most susceptible to infection. Fungicides such as captan, azoxystrobin, fenbuconazole, propiconazole, and others a b c applied at leaf emergence are recommend- Figure 11-14. (a) Mummy ed; repeat according to label instructions. berry twig blight. (b) Foliar Resistant cultivars include: Duke, Elliot, Late symptom. (c) Infected ber- Blue, Northsky ries on branches. (d) Mum- mies look like tiny black pumpkins. (e) Mummy berry apothecia.

d e

35 to infect newly emerging green tissue. Figure 11-15. (a) Anthracnose fruit rot causes ripening berries to decay rapidly. (b) Masses of A different type of spore (conidia) is spores appear as an orange ooze on infected produced on resulting dead tissue in the berries. early spring as flowering begins. Infected Anthracnose fruit rot/ripe rot blossoms smell like fermented tea and Disease Management attract insects. Conidia can be carried If disease becomes a problem, fungicides to flowers by insects and wind. should be applied at regular intervals begin- Anthracnose fruit rot/ripe rot, caused by ning at full bloom. Suggested fungicides the fungi Colletotrichum acutatum or C. include captan, azoxystrobin, and pyraclos- trobin. gloeosporioides, results in both pre- and Pick fruit frequently as it ripens. Do not allow post-harvest fruit rots. Rabbiteye variet- fruit to become overripe. ies are less susceptible than highbush Rapid postharvest cooling is critical for inhibi- blueberries. Early symptoms include tion of postharvest rot. blighted blossoms; leaf spots or twig le- a Resistant cultivars include: Brigitta Blue, Elliot, sions may develop later in the season. In- Hannah’s Choice, Legacy, Little Giant, Morrow, Murphy, Reveille fected twigs develop dark brown lesions Highly susceptible cultivars include: Berkeley, that are surrounded by spore-producing Bluecrop, Bluetta, Blueray, Bounty, Chanticleer, structures (acervuli). While this disease Coville, Harrison, Jersey, Spartan is primarily a fruit rot, leaf infections resulting in reddish-brown spots can also occur. Ripening berries decay rapidly, (Figure 11-15a) and orange spores usually ooze from infected berries (Figure 11-15b). The fungus overwinters in blighted twigs and old infected fruit on the ground. Spores are released during rainy b periods throughout the season. Infection can occur anytime. Green berry infections remain latent (dormant) until fruit Figure 11-16. Phyllosticta leaf spot. begins to ripen, when temperatures range between 68° and 80°C, and leaf wetness Phyllosticta leaf spot and fruit rot exceeds 12 hours. Disease Management Phyllosticta fruit rot and leaf spot, Maintain a clean field floor; caused by Phyllosticta vaccinii or P. rake or cultivate fallen diseased leaves. elongate, is a disease of highbush and rab- Avoid susceptible cultivars, such biteye blueberries. Foliar symptoms are as: Jersey, Murphy, Harrison described under “leaf spots,” above (Fig- Limit overhead irrigation. ure 11-16). Fruit symptoms may develop Space and prune bushes to re- in late spring, but most often develop duce humidity and to promote during storage. Infected fruit contain nu- rapid drying of tissue. If disease becomes a problem, merous speckles or small circular spots fungicides may be applied after with purple margins. Lesions become harvest until leaf drop in order hard, gray, and slightly depressed. Fungal to control subsequent infec- fruiting bodies (pycnidia) may develop in tions. centers of lesions. Fungi overwinter in infected tissue that falls to orchard floors. Rain disperses spores (conidia). Infection occurs during mid-season, but visible symptoms do not occur until fruit ripening.

36 Viruses and Phytoplasmas Figure 11-17. (a) Oakleaf pattern symptom of shoe- Shoestring virus is a widespread virus string virus. (b) Reddish elon- that is especially prominent in the eastern gated streaks on branches infected with shoestring United States. Symptoms of shoestring virus. (c) Pink to red discol- virus appear approximately 4 years after oration of blossoms due to infection. Leaves appear red or purplish shoestring virus. along midribs (Figure 11-17a) and at bases of leaves. Red or purplish, elongated, strap-like leaves are also characteristic of this disease (Figure 11-17b). Green stems may develop red, elongated streaks, especially stems exposed to sun. Infected plants contain reddish flowers (Figure 11-17c) and purple fruit. a b c The virus is vectored by the blueberry aphid Illinoia pepperi, which acquires Shoestring virus the virus upon emergence in spring and Disease Management transmits it through the growing season. Plant virus-indexed (virus-free) plants from a reputable nursery. Tomato ringspot virus can cause a serious Apply insecticides when aphids emerge. disease on the West Coast. It is rare in the Inspect plantings frequently and remove and destroy infected plants. Diseased bushes can- Midwest, but has occurred in Pennsylvania. not be cured. They must be removed from the field as soon as they are diagnosed. Symptoms include cupped and malformed Resistant cultivars include: Bluecrop leaves with numerous small, necrotic spots. Young leaves may be strap-like and mottled Figure 11-18. Strap-like, mottled leaves result- (Figure 11-18). However, symptoms vary ing from tomato ringspot virus. from plant to plant and within the same Tomato ringspot virus plant. Infected plants defoliate by mid- Disease Management harvest and die after severe winters. Plant virus-indexed (virus-free) plants from a The virus is spread by dagger nematodes reputable nursery. (Xiphinema spp.) that are often present in Inspect plantings frequently and remove and soil. The virus has a wide host range, so destroy infected plants. disease may be transmitted from many Control weeds to reduce inoculum. Diseased bushes cannot be cured. They must different plant species from one plant to be removed from the field as soon as they are another. Disease spread within a field is of- diagnosed. ten slow. Infection may also be seed-borne. Leaf mottle virus is not common in the Midwest, but is has been reported in Michigan. Symptoms include mottling patterns and puckered leaf spots (Figure Figure 11-19. Pale, puckered terminal leaves due to leaf mottle virus. 11-19), which usually are not observed until 3 to 4 years after infection. Symp- Leaf mottle virus toms differ with cultivar: infected Rubel Disease Management plants usually have dead stems, while Plant virus-indexed (virus-free) plants from a reputable nursery. Jersey and Blueray become stunted upon Inspect plantings frequently and remove and destroy infected plants. Diseased bushes cannot be cured. They must be removed from the infection and small rosette terminal field as soon as they are diagnosed. leaves develop. The virus is spread by Monitor sources of beehives to limit introductions of the virus to pollen, which is carried by bees. orchards. Red ringspot is a viral disease that is most commonly found in the eastern Figure 11-20. Foliar symptoms of red ringspot. United States. Symptoms include red spots or circular blotches on stems and Red ringspot reddish-brown circular spots on upper Disease Management sides of mature leaves (Figure 11-20) in Plant virus-indexed (virus-free) plants from a reputable nursery. mid- to late-summer. Similar circular Inspect plantings frequently and remove and destroy infected plants. blotches may develop on infected fruit. Diseased bushes cannot be cured. They must be removed from the field as soon as they are diagnosed. Use insecticides to control insects.

37 The virus is vectored by mealy bugs. Figure 11-21. Foliar symptoms of blueberry mosaic virus. Blueberry mosaic virus is commonly found in both the eastern and western Blueberry mosaic virus United States. Symptoms include mosaic Disease Management patterns of red, yellow, green, and pink Diseased bushes cannot be cured. They must (Figure 11-21). Symptoms may not be be removed from the field as soon as they are diagnosed. produced every year, as they seem to be temperature-dependent. On infected plants, fruit ripens late and is of poor quality. The virus is spread through cuttings, but not through mechanical means such as tools. No known vector has been reported. Little else is known about this virus. Blueberry stunt was originally thought to be caused by a virus but is now known to be caused by a phytoplasma. The only known carrier is the sharpnosed leafhopper (see Chapter 12: Insect and Mite Pest Management), though other vectors may Figure 11-22. (a) Short bushy growth at the exist. base of a bush infected with blueberry stunt. (b) Downward cupping of leaves with marginal Symptoms vary with stage of growth, chlorosis typical of blueberry stunt. time of year, age of infection, and the cultivar. Symptoms are most noticeable Blueberry stunt during mid-June and late-September. Disease Management Plant virus-indexed (virus-free) plants from a Affected plants become dwarfed, devel- reputable nursery. oping shortened internodes, excessive Diseased bushes cannot be cured. They must branching, and low vigor (Figure 11- be removed from fields as soon as they are 22a). Small, downward-cupped leaves diagnosed. turn yellow along margins and between a Removal of bushes may facilitate the further lateral veins (Figure 11-22b), giving a spread of the disease in the field. Agitation of the bush during removal will dislodge green and yellow mottled appearance. leafhoppers, causing them to move to a These mottled areas turn brilliant red neighboring healthy bush. Therefore, infected prematurely in late summer, although bushes should be sprayed with an appropriate the midrib remains dark bluish-green. insecticide prior to removal. Susceptible cultivars include: Bluetta, Jersey, Fruit on affected bushes are small, hard, Weymouth lack flavor, ripen late (if at all), and remain Resistant cultivars include: Rancocas attached to plants much longer than on healthy plants. b Additional Resources Compendium of Blueberry and Cran- berry Diseases. American Phytopatho- Midwest Commercial Small Fruit and logical Society, 3340 Pilot Knob Road, Grape Spray Guide, ID-94. http:// St. Paul, Minnesota 55121. Phone: www.ca.uky.edu/agcollege/plantpa- (612) 454-7250 or (800) 328-7560. thology/ext_files/PPFShtml/ID-94. This is the most comprehensive book pdf. on blueberry diseases available. All Midwest Small Fruit Pest Manage- commercial growers should have a copy. ment Handbook, B-861. http://www. Highbush Blueberry Production Guide. ca.uky.edu/agcollege/plantpathology/ Northeast Regional Agricultural ext_files/PPFShtml/MwSmFruitPM- Engineering Service, 152 Riley-Robb Handbook.pdf. Hall, Cooperative Extension, Ithaca, NY 14853. Phone: (607) 255-7654. This is a comprehensive book covering most phases of blueberry production.

38 Chapter 12 Insect and Table 12-1. Blueberry Insect Pest Monitoring and Control Relative to Crop Phenology. Mite Pest Management

General Management Principles Dormant Bud swell tip Bud break/Green expansion cluster/shot Tight pink bud Early pink bug Late bloom Early bloom Full fall Petal fruit Green coloring Fruit 25% blue 75% blue Postharvest Introduction to Scouting. Blueberry bud mite + + + + + + + + + + + + + + Regular Cutworm +++ scouting for pests is an essential ele- Blossom weevil ++++++ ment of Integrated Pest Management in Oblique-banded leafroller + + + + + + + + + blueberries. The pest scouting calendar Eastern tent caterpillar + + + + (Table 12-1) can be used to begin and Cherry fruitworm + + + + + + end scouting for a particular pest. This Cranberry fruitworm + + + + + can consist of visual inspection of the Blueberry aphid ++++++ crop and monitoring insect traps. By Plum curculio* ++++ + checking the planting in this way, trends Sharp-nosed leafhopper + + + + + + in pest populations can be identified and Oriental beetle +++ the efficacy of pest management activities Flat-headed apple tree borer +++ Azalea stem borer + + + can be assessed. Monitoring traps are Blueberry maggot + + + + efficient tools for checking pests; traps Japanese beetle ++++ are available for fruitworms, blueberry Spotted wing drosophila + + + maggot, spotted wing Drosophila, and Bagworm +++ other key pests. Maintaining a weekly Green June beetle + + record of insect captures in these traps Yellow-necked caterpillar + will provide early warning of pest activity Fall webworm + and the need for management.  Usual time for monitoring and control Weekly checks of 100 growing shoots  Less risk, monitoring or control may be required + Potential pest activity and 100 fruit clusters spread through the * In the southern region of the Midwest, only summer generation plum curculio larvae have been field are also a good basis for making de- found in ripening berries from mid-June to the end of harvest. cisions on whether some other pests are present, and at what level. Pest pressure is often greater towards the edge of a plant- regular ral enemies is encouraged. Providing ar- ing, so selecting some samples at the field pressure can be minimized by pruning eas designated for flowering plants during edge and others in the field interior will to remove older canes (typically the summer months can increase para- provide a perspective on whether pests the larger 4-year-old wood) and also by weed control. sitic wasps and other beneficials, More show greater abundance in one area. effective This helps remove information is available at http://www. Record scouting information in a sites in which pests hide from natural nativeplants.msu.edu. Natural enemies notebook for comparison from season to enemies and improves the effectiveness such as lacewings and lady beetles can season. After a few years this will provide of other management techniques (see also be purchased, but there is relatively information on annual trends and give below). Resistant cultivars little information on their survival and the grower a clearer view of when and are also an effective effectiveness. where certain pests develop on the farm. strategy for avoiding pest problems. For example, some popular varieties, such While non-chemical approaches are Non-chemical Approaches as Bluecrop, are resistant to shoestring encouraged, production of fresh blueber- Blueberries have a relatively small virus and selection of these varieties can ries can be challenging when invasive pest complex compared with some other avoid the need for aggressive aphid con- species such as Japanese beetle and crops, but there are some key insect pests trol to prevent infection. Local blueberry spotted wing Drosophila, or the native that can defoliate bushes or infest fruit recommendations can assist growers in pest blueberry maggot, are present. For making it unsellable. Pests like eastern selecting cultivars that are resistant to these direct pests, it may be necessary to tent caterpillars, bagworms, fall web- local pest complexes. take a more intensive approach to their Biological control worms, and yellownecked caterpillars can contribute to the management to ensure the high-quality can all be easily removed by hand. Pest suppression of many pest populations, fruit that customers expect. and so the use of tactics to support natu-

39 Spray Techniques. There are various Insects and Mites of Blueberries registered insecticide options for use in The primary insect pests of blueber- blueberry, and these range from highly ries in the Midwest Region are cranberry selective and biological insecticides fruitworm, Japanese beetle, blueberry to broad-spectrum insecticides that maggot, and spotted wing Drosophila. require applicator certification. Local Additional insect pests include plum cur- Extension agents can assist with product culio, blueberry tip borer, whitemarked recommendations suitable for local pest tussock moth, blueberry aphid, Putnam complexes. scale, and gypsy moth. In order for pesticide applications to control the target insect pest(s), it is es- Insects That Attack Blueberry Buds a sential that the spray reaches the target. Climbing cutworms (Order: Lepidop- This may sound simple, but factors such tera; Family: Noctuidae) are nocturnal as bush architecture, weed density, pest insects that feed on swollen blueberry behavior, and insecticide type can all in- buds during the evening hours. They fluence the effectiveness of spray coverage. hide under vegetation or stones, or bur- Well-pruned canopies allow for good row into the ground during daylight. The b air movement and lower disease pres- extent of damage varies from year to year Figure 12-1. (a) Several climbing cutworm sure, but they also allow for improved and site to site. species. (b) Cutworms curl up tightly when spray penetration. This, coupled with Mature cutworm caterpillars are 1¼ disturbed. good weed control, can greatly aid in the inches long, with a smooth, light brown Climbing cutworms success of spray programs by allowing body, a dark brown head, and five pairs Monitoring and Management greater opportunity for contact between of fleshy prolegs on the abdomen (Figure Scout daily at bud swell for hollowed out, the pesticide and the insect pest. 12-1a). Typically, cutworms will curl up damaged buds. In general, insecticide applications tightly when disturbed (Figure 12-1b). Apply insecticide if more than 2 percent of the buds are damaged. need to have sufficient water as the car- Blueberry bud mite (Acalitus vaccinii) rier, along with sufficient air speed to causes blistering on outsides of bud transport the pesticide to its target. Some scales, poor flower set, poor plant growth, pests, such as blueberry maggot fly, can and reduced fruit set, particularly in the Females reproduce rapidly, laying clear, be well-controlled by a spray that covers tops of plants. spherical eggs, and producing multiple leaves and fruit. In this case perfect cov- Sample the current season’s growth generations each year. The mites live on erage is not essential because the insect after harvest and dissect floral buds the inner bud scales from fall to spring; walks over the bush surface during the nearest to shoot tips; a microscope will feeding injury becomes evident when week from emergence to the start of egg be needed to see the tiny white mites. populations build to high levels. laying. In contrast, the cranberry fruitworm moth lays its egg inside the calyx cup of the berry, and the larva crawls around the berry to enter at the stem end. There is consequently a short period of time and a very specific area that must be covered for this insect to be controlled. A range of sprayer designs can be effective at providing good coverage of blueberry bushes. Whether using airblast sprayers, tower sprayers, or cannons, calibration of the sprayer should be done before each season. Adjustments should a b c also be made to ensure that the spray is Figure 12-2. (a) Rossetted and (b) desiccated bud and (c) blueberry fruit growing from bud focused in the appropriate part of the infested with blueberry bud mites. bush. For example, Japanese beetle and Blueberry bud mite blueberry maggot are most active on the Monitoring and Management top of the bushes, whereas spotted wing From February through April the presence of bud mites is relatively easy to detect by looking Drosophila can attack fruit anywhere on for the distinctive red blisters on bud scales. the bush, but they particularly prefer the Selectively prune out old canes to help reduce bud mite populations in established plantings. shady interior of the canopy. When infestations are severe, 2 applications of an approved miticide (1 month apart immediately following harvest) should give adequate control. Apply sprays before mites penetrate too deeply into the buds and destroy the tissues that produce the next year’s fruit.

40 Insects That Attack Blueberry b Figure 12-3. (a) East- ern tent caterpillar Flower Clusters and/or Berries egg mass on pencil- Eastern tent caterpillar (Malacosoma sized terminal, (b) larva, and (c) larvae americanum) nearly-mature larvae dis- on silk nest in branch perse from infested trees adjacent to fruit crotch. plantings. Development is completed by feeding on and defoliating blueberry plants, often during bloom. Larvae have a white line down the center of the back, plus a series of light blue and black dots, and are 2 to 2½ inches long when fully grown (Figure 12-3b). They produce silk nests (tents) in crotches of fruit trees (Figure 12-3c); this group of a c larvae can defoliate trees. Once the host Eastern tent caterpillar is defoliated, the nearly mature larvae Monitoring and Management disperse to adjacent plants like blueber- Remove and destroy egg masses during winter pruning ries where they feed on buds, flowers, and Scout wild cherry trees as they begin to leaf out. leaves, defoliating these plants as well. Remove silk nests and larvae from tree crotches and bushes. Mature larvae disperse to protected areas Insecticides are usually not warranted. to pupate. In midsummer, adults emerge, mate, lay egg masses on pencil-sized ter- Figure 12-4. (a) minals on fruit trees (Figure 12-3a), and Male cranberry overwinter. fruitworm moth, (b) Cranberry fruitworm (Acrobasis vaccinii) cranberry fruitworm male moths are brown and elongate with egg (arrow), and (c) a cranberry fruitworm white triangular patterns on the wings larva and damage. (Figure 12-4a). The females lay white oval eggs (Figure 12-4b) in the calyx cup starting at early petal fall. Larvae are green with a brown head and covered with fine hairs. b The insect overwinters in leaf litter under the bush and is also present on wild blueberry in the woods. Moths emerge during early bloom and lay eggs. Egg hatch typically starts while blueberries are still in bloom. Larvae infest fruit in the early part of the season (Figure 12-4c). There is one generation per year. Cherry fruitworm (Grapholita pack- ardi) larvae feed inside individual berries a c after making a tiny entry hole in the berry Cranberry fruitworm wall. However, since little visible damage Monitoring and Management occurs to the fruit exterior, infestations Control weeds and remove wild hosts may be difficult to detect. Infested berries Deploy monitoring traps at wooded borders prior to bloom and check often turn blue prematurely. weekly. Egg hatch begins at about 100 growing degree days (GDD) The moth is 6 mm (1⁄4 inch) long, dark base 50°F from the first sustained catch of moths. brown-gray, with a mottled silver pat- The most important spray is at petal-fall. In high-pressure sites, an additional, earlier application at the predicted start of egg hatch will tern. Eggs are round, flat, and shiny. The improve control. larva resembles cranberry fruitworm, but cherry fruitworm has a dark head capsule and a reddish body, reaching 9 mm (about Cherry fruitworm 1⁄3 inch) in length. Monitoring and Management Moths typically begin egg laying at Infested berries often drop prematurely before harvest, thus they are not a high risk as a harvest contaminant. first petal fall. Eggs are laid in the calyx. Insecticides used for management of cranberry fruitworm typically Larvae often enter berries in the calyx or control this pest, though early activity may require a specific spray. on the berry side.

41 Blueberry maggot (Rhagoletis mendax) activity is first determined by monitoring traps. The first symptom of blueberry maggot infestation is typically seen as soft fruit with white maggots (Figure 12-5b). Blueberry maggot adults (5 mm long) have distinctive ‘W’ or ‘M’ wing pattern (Figure 12-5a). The legless maggot is white a b c with black mouthparts and grows to 7 Figure 12-5. (a) Blueberry maggot fly with distinctive wing pattern, (b) legless blueberry mm (a little more than 1⁄4 inch) in length. maggot larva and (c) baited monitoring trap placed in a blueberry bush. The blueberry maggot overwinters as Blueberry maggot pupa below the soil surface. Most pupae Monitoring and Management emerge 1 year after going into the soil. Use baited yellow sticky traps baited with ammonium acetate (or ammonium carbonate) as a Adult emergence typically begins in mid- food attractant (Figure 12-5c). Deploy traps before the first anticipated flight in late June. to late June, especially after rain, with Place traps on a stake or hang on an upper branch of a blueberry bush in a perimeter row adult flight continuing through August. (south facing side of bushes). Hang traps with the colored side down in a V-orientation (Fig- ure 12-5c). Female flies lay eggs 7 to 10 days after Check traps weekly starting at 700 GDD base 50°F until the first fly is caught, triggering fruit emergence, placing them under skins protection activities. of ripening blueberries with a single egg Use recommended insecticides, which kill the adult fly on contact, preventing it from laying deposited per fruit. eggs into the fruit. Spotted wing Drosophila (Drosophila A boil test can be used with ripe fruit to sample for maggot infestation. suzukii) adult male flies have a spot on each wing (Figure 12-6a). Females lack Figure 12-6. (a) Male spotted wing dro- wing spots but have serrated ovipositors sophila fly and (b) a spotted wing drosophila (egg-laying device) used to cut a slit into the larva on a blueberry (bottom) in comparison skin of intact fruit in order to lay eggs. Flies to a larger blueberry maggot larva (top). are 1.6 to 3 mm (1⁄16 to 1⁄8 inch) long, and Spotted wing Drosophila look similar to the small vinegar flies that Monitoring and Management typically infest fruits and some vegetables Trap flies with a simple monitoring trap. in late summer. Infested berries soften, • Use a plastic 32-oz cup with ten 3⁄16 inch become leaky, and contain small legless, holes around the upper side of the cup; leave a 3- to 4-inch section without holes cylindrical, white maggots (Figure 12-6b) a to facilitate pouring out the liquid bait. The with black mouthparts that are approxi- small holes allow access to vinegar flies, mately 3 mm (1⁄8 inch) long at maturity. but keep out larger flies, moths, bees, etc. Mature female flies overwinter and • A small yellow sticky trap can be hung on a paper clip inside traps to trap flies. become active before fruit ripening. Mul- • Bait the traps using a mix comprised of 1 tiple generations occur each year, with tablespoon of active dry yeast and 4 table- populations building in late summer. As spoons of sugar per 12 oz of water. • Hang traps in a shaded area in the fruit fruit start ripening, females begin laying zone. eggs into fruit. Fly abundance increases • Check traps and change the bait weekly. throughout the blueberry harvest sea- • Identification of flies can be aided by infor- son, with greater pest pressure for later- mation available at http://www.ipm.msu. b ripening varieties. edu/SWD.htm. Plum curculio Fruit can also be sampled for spotted wing (Conotrachelus ne- Drosophila using a boil test (also used to nuphar) does not just attack plums; hosts test for blueberry maggot) or by placing also include blueberries, peaches, apples, less, brown-headed grubs, about 6 to 9 crushed berries in a strong salt solution (1⁄4 pears, and an array of wild and cultivated mm long (1⁄4 to 3⁄8 inch). cup of salt in 1 quart of water). Wait 10 to 20 minutes and look for white larvae. fruits. Adults overwinter by finding protec- Pick berries before over-ripening and soften- Adult plum curculios are small tion under debris on the ground. They ing and keep fruit cool after harvest to slow brownish-black snout beetles, about 4 to emerge from hibernation in early spring insect development. 6 mm (1⁄8 to 1⁄4 inch) long, mottled with when daytime temperatures reach a Complete insecticide coverage of the lighter gray or brown markings (Figure consecutive high temperature for 3 to 4 canopy and timely response to fly activity are important for effective control. 12-7a). The mouthparts are at the end of days. Adults feed on all new growth tis- a moderately curved snout that is about sues in spring. As soon as new fruit are one-fourth the length of the body. Larvae formed, egg laying begins and will last are slightly curved, yellowish-white, leg- for 3 or 4 weeks. The female will create a

42 small pocket for the egg on the outside of the fruit. Females can lay 50 to 160 eggs which hatch within a week. Larvae emerge within 10 to 16 days. Larva will then bur- row into the soil and in approximately 5 weeks, they emerge as adults. The summer brood, which emerges in late July and Au- gust, feeds on fruit but does not lay eggs. Cranberry weevil (Anthonomus muscu- a b c lus) is also known as the blueberry blos- Figure 12-7. (a) Plum curculio adult, (b) feeding scar on blueberry and (c) legless, white larva som weevil. Adult female weevil activity with brown head capsule inside a blueberry. is evident by holes in flower buds. Grub Plum curculio feeding within the bud prevents flower- Monitoring and Management ing and causes injured buds to drop to Keep planting floors closely mowed after harvest to eliminate protective cover for overwin- the ground. tering. The cranberry weevil is 1.6 to 3 mm Destroy nearby plum thickets, abandoned fruit blocks, and other alternate hosts to reduce (1⁄16 to 1⁄8 inch) long with white flecks on dispersal from outside sources. Monitor insects with a baited, gray pyramid Tedders trap, set out before bloom. Place it along wing covers and a snout nose (Figure 12- perimeters of plantings, adjacent to woodlots. Check traps weekly. 8). The grub is small, legless, and yellow- Once adults are detected, begin checking berries for the presence of feeding scars. white with a brown head. Use insecticides to protect berries if feeding damage is detected. The weevil adult overwinters in wooded areas and moves to blueberry bushes as early as bud swell. The adult Figure 12-8. Adult cranberry blossom weevil. chews a hole in a blossom bud and lays a Cranberry weevil single egg. Injured buds fall, larva feed in- Monitoring and Management side and later pupate in the buds. Adults Cultural controls, such as clean cultivation may be used emerge in late spring to feed on leaves. for low infestations. There is typically one generation per year. When there is a history of weevil damage, check for Green June beetle damaged blossom buds or weevil presence as the first (Cotinis nitida) are blossom buds develop. To detect weevils, use a sweep attracted to and feed as a group on the net or shake them onto a white ground cloth. ripening berries. Once weevil damage or weevils are detected, apply a Adults are about 19 to 25 mm (¾ to 1 recommended insecticide. inch) long and have green forewings with light brown margins (Figure 12-9b). The larva is a legged, C-shaped grub (Figure 12-10c) that crawls on the ground on its back (Figure 12-9a). In late June and July, after rain has moistened and loosened the soil, adults emerge. Females lay eggs in soil beneath the grass surface where compost or green manure has been applied. Eggs hatch in mid-summer and larvae feed until the following May on decomposed manure a and vegetable matter in the soil. Adults feed for about a month on ripening fruit.

Green June beetle Monitoring and Management In July, scout weekly to detect dispersal into blueberry plantings and identify first adult feeding damage. Manually remove or apply insecticides after first damage is detected.

b c Figure 12-9. (a) Green June beetle larva moving on back, (b) adult, and (c) feeding aggregation on ripe grapes.

43 Insects That Attack Blueberry Foliage Figure 12-10. (a) Leaf and fruit damage, (b) adult Japanese beetle, and (c) comparison of scarab bee- Japanese beetles (Popillia japonica) re- tle adults (left) and “C”-shaped grubs (right) in turf: move skin of fruit and skeletonize leaves 1) green June beetle, 2) May beetle (Phyllophaga), 3) masked chafer, 4) Japanese beetle, and 5) black (Figure 12-10a). turfgrass Ataenius. Adults are about 13 mm (1⁄2 inch) long, with shiny metallic brown wings, a green Japanese beetles prothorax and head, and a series of white Monitoring and Management spots on the edge of the abdomen (Figure Do not use commercial Japanese beetle traps near plantings because traps attract additional beetles. 12-10b). Grubs are C-shaped and have a Scout blueberries in June or July. distinctive pattern of hair on the hind Remove beetles by hand or apply recommended end of the abdomen (rastral pattern) of 14 foliar insecticides. hairs in a V-shape on the abdominal tip. Remove wild hosts such as wild grape, raspberry, The rastral pattern distinguishes it from and blackberry. other grubs species found in soil under Maintain cleanly cultivated fields to reduce suit- turf (Figure 12-10c). ability for beetle development. Soil insecticide may be necessary in grassy fields to During fruit ripening and through the reduce populations. harvest season, beetles emerge from the There is a low tolerance for beetle contamination soil. Eggs are laid in the soil under turf, in picked fruit, so thresholds are essentially zero. a and larvae feed on roots of grasses and other plants, but not on blueberry. Bagworms (Thyridopteryx ephemerae- 1 formisz) defoliate blueberry plants (Figure 12-11a), leaving behind brown spindle- shaped bags attached to leaves (Figure 12-11b) and limbs (Figure 12-11c). Bags are made from the cemented leaf parts of 2 the host plant and each contains a single caterpillar. As caterpillars grow, bags can increase to 2 inches in length. Bags are most noticeable during winter 3 after leaf fall. Overwintering bags contain eggs that hatch in June or July. In late summer, caterpillars pupate inside bags and 4 later develop into adult moths. Female moths are wingless, remain in bags, and b 5 c attract winged males. Mated females lay 500 or more eggs inside bags and then die.

Figure 12-11. (a) Bagworm defoliated blueberry plant, (b) bagworms on underside of blueberry leaf and (c) a bag hanging from a branch.

Bagworms Monitoring and Management Begin scouting plantings for bagworm bags during winter pruning. Mechanically remove and destroy overwintering bagworms. Scout plants again in mid-June after larvae have dispersed into planting and then remove and destroy bags.

a b c

44 Fall webworm (Hyphantria cunea) skeletonizes leaves within a protective web. Though the webs are very unsightly, damage to most plants is considered to be insignificant if webs are removed soon after development. Fall webworm is most often discov- ered when the light gray, silken webs (Figure 12-12c) appear in the planting in June and July (1st brood) and August a through September (2nd brood). Web- worms enclose leaves (Figure 12-12a) and small branches (Figure 12-12b) in their silk nests. This distinguishes them from tent caterpillars, which make a smaller nest in the crotch of trees (Figure 12-3c). Webworm caterpillars, which are covered with long to yellowish tan hairs, b remain inside webs; if food runs out, new foliage is encased. Yellownecked caterpillar (Datana min- istra) occasionally results in outbreaks that may completely defoliate one or a more plants. Full-grown larvae are about 2 inches long with a black body and black head. A bright orange-yellow spot characterizes the “neck” area behind the head. The remainder of the body is marked with four longitudi- nal yellow stripes interspersed with black, and the entire body is clothed with long, soft, white hairs (Figure 12-13b). Larvae c b feed in large colonies on leaves near the tips Figure 12-12. (a) Newly hatched group of Figure 12-13. (a) Feeding aggregation of fall webworm caterpillars on birch leaf, (b) yellownecked caterpillars and (b) U-shaped of twigs and branches (Figure 12-13a). caterpillars defoliating leaves inside silk nest, defensive posture. Pupae overwinter in soil. Adults and (c) damage to blueberry plant. emerge in mid-summer, laying masses of Fall webworm Yellownecked caterpillar 50 to 100 eggs each. Emerging caterpillars Monitoring and Management Monitoring and Management feed as a group, resulting in plant defolia- Scout plants from late-June through Sep- Scout every 2 weeks beginning in June or tion as caterpillars mature. There is one tember for webs. July. generation per year. Prune or pick off the nests and larvae while It may be faster to remove larvae by hand Leafrollers, such as the obliquebanded they are still small. than to spray. leafroller (Choristoneura rosaceana) and Do not burn or torch the nests while on If an insecticide is used, spray entire plants, bushes as this may do additional damage to not just colonies. redbanded leafroller (Argyrotaenia velu- the plants. tinana) can be found on blueberries. Obliquebanded leafroller larvae are green with dark heads and are about Leafrollers 25 mm (1 inch) long when fully grown. Monitoring and Management Moths are about 18 mm long with wings Leafrollers are usually controlled by natural enemies or by sprays applied for other pests. that are banded with tan to brown scales. Insect growth regulator insecticides can be highly effective. Redbanded leafroller larvae are small (up Pheromone traps can be used to determine adult emergence. Trap information can be combined with growing degree-days to predict egg hatch, larval to 16 mm long) and green or pale yellow. development, and optimal timing for control. Moths (6.3 to 9.5 mm long) are reddish- Timing of treatment depends on the type of insecticide. brown with faint tints of grey and orange; wings have a distinct reddish-brown band.

45 The obliquebanded leafroller is one of Figure 12-14. The distinctive larva of the white- the most damaging leafroller species and marked tussock moth. can feed directly on fruit during the summer. First-generation larvae are active Whitemarked tussock moth before and during bloom, and sprays for Monitoring and fruitworm typically control first genera- Management Prune out egg masses tion leafrollers. Focus scouting on flower during winter. buds and look for webbed flowers and Control weeds in fields. leaves. The summer generation larvae The first generation of this are active during fruit ripening, feeding pest is typically controlled on fruit and foliage. They also feed on by insecticide sprays for cranberry and cherry fruit- flower clusters, leaves, and green fruit. worm. Effective control Larvae feed inside the webbing and may early in the season usually be hard to find. Redbanded leafroller avoids late-season prob- larvae may be present as soon as green lems with the larvae. foliage appears, and this first generation can injure leaves and young clusters. The Adult borers (9 to 18 mm long) emerge below a bud. Eggs are inserted under the later generation rarely causes injury. from mid-May through June and feed bark between two rows of holes (Figure Whitemarked tussock moth (Orgyia on the underside of the leaves along the 12-15b), causing the first 3 to 4 inches of leucostigma) does not cause significant mid-vein. Callus tissue forms around the the current season’s growth to wilt and feeding damage to mature bushes, but injured vein and the leaf may curl abnor- die in June (Figure 12-15c). Larvae (Figure it can defoliate young blueberry plants. mally. In late-May to June, adult females 12-15a) then bore down into roots where Larvae have irritating hairs, and the sec- lay eggs in new shoots several inches they overwinter. ond generation can cause problems for pickers or contamination of harvested fruit. Figure 12-15. (a) Azalea stem borer larva. (b) Two rows of chewed holes on terminal Female moths are white and flightless; where egg is laid causes (c) tip to wilt, and (d) they create a large egg mass wrapped sawdust appears at base of cane as evidence of inside a dried leaf that is typically stuck larval tunneling. to a blueberry branch. Male moths are Azalea Stem Borer brown with feathery antennae. The Monitoring and Management 1½-inch larvae are very distinctive with In midsummer, look for infested twigs that yellow stripes, yellow and red tufts, and a are wilting, are breaking off at the base, have many fine white hairs on the black body coarse sawdust-like frass at the base of the plant, or are dying. (Figure 12-14). Remove and destroy wilting branches, pruning Insects That Attack the Blueberry low enough to remove larvae. Roots, Canes and Terminals A history of azalea stem borers may require insecticide applications during the egg laying Azalea Stem Borer (Oberea myops) period (applied in mid-May and again in early chews two rows of holes (Figure 12-15b) June). into terminals, causing girdled canes to wilt (Figure 12-15c) and often die. Larval b tunneling can be detected by the accumulation of sawdust at the cane (Figure 12-15d). Adult beetles are about 13 mm (½ inch long), with long black antennae, tan wings with darkened margins, and two black spots on their orange pronotum (upper surface of the prothorax) behind the head. Larvae are creamy-yellow with a brown, round head capsule.

c d

46 Blueberry tip borer (Hendecaneura shawiana) infests the current year’s shoot growth, feeding inside the stem (Figure 12-16b). The larva’s point of entry is usually visible as a small (1 mm diameter) brown pinhole on the side of the stem. Foliage above the feeding site turns brown from the leaf tip (Figure 12-16a). Borer damage can also reduce fruit set for the following year. a b The moth is about 9 to 14 mm (about Figure 12-16. (a) Symptomatic terminal leaves as (b) blueberry tip borer larva tunnels in the ½ inch) long with mostly brown wings. stem. Each front wing has orange marks near the tip and a silver spot along the hind Blueberry tip borer margin. Larvae are slender, light pink Monitoring and Management caterpillars. There is no effective trapping system. Larvae enter shoots soon after hatch- Scout weekly to detect early symptoms. Remove and destroy infested shoots to reduce risk for infection the following year. Larvae ing from an individual clear egg laid on inside pruned shoots will dry out and die as the shoots desiccate. young stems. Larvae feed and tunnel Fields with high levels of infestation should be treated with insecticides during predicted inside stems. Larvae are visible with a time of egg laying. This period overlaps with cranberry fruitworm activity. hand lens if an infested stem is broken open. Insects pupate in stems and emerge the following year. Moth flight occurs during mid- to late-June around the time of fruitworm activity. There is only one generation per year. Scale (Terrapin scale, European fruit Lecanium, Putnam scale) can infest fruit or stems, resulting in blemished fruit and sooty mold on berries. Scales suck sap from plants and can reduce bush vigor. Scales are small 2 to 3 mm round or oval dots with waxy protective coverings (Figures 12-17a and b) that shelter the small yellow insects. a b Different scales have varying life Figure 12-17. (a) Scales can infest berries and (b) stems. cycles, but all overwinter on plants. Egg- laying stage in the spring or summer Scale is followed by a period when crawlers Monitoring and Management emerge from the scales seeking places to Remove infested canes during winter pruning. settle and feed. Crawlers are susceptible Apply a delayed-dormant application of oil if populations are high. to insecticides. Monitor emergence of Specialized, scale-specific growth regulators are also available. crawlers using double-sided sticky tape placed around branches. Figure 12-18. A blueberry aphid feeding on a Insects That Feed on Blueberry blueberry leaf. Sap (disease vectors) Blueberry aphid Blueberry aphid (Illinoia pepperi) Monitoring and Management causes deformed and wilted leaves on Protect natural enemies such as lacewings and ladybeetles. new growth that can indicate an aphid If chemical control is required, the newer sys- infestation. Severe infestations can re- temic insecticides are highly effective. duce the formation of fruiting buds for Reduce weeds, which can reduce effective the subsequent year’s harvest. Aphids insecticide coverage. constantly produce honeydew, which If shoestring virus symptoms are present (see Chapter 11), more active aphid management can lead to sooty mold outbreaks on is needed to prevent movement of the virus fruit and foliage. They are also vectors of between bushes.

47 blueberry shoestring virus (see Chapter 11: Blueberry Diseases) that can cause decline of susceptible blueberry cultivars. Aphids colonize undersides of leaves on lower new shoot growth. They are 2 to 4 mm long and green with long legs and antennae (Figure 12-18). Aphids hatch from overwintering eggs during early bloom and colonies slowly increase. Aphids grow fastest on new young growth, especially on heav- ily fertilized bushes. Warm weather also promotes faster growth, and populations a b can grow quickly through May and June. Blueberry sharpnosed leafhopper Figure 12-19. (a) Blueberry stunt infected plant and (b) sharpnosed leafhopper. (Scaphytopius magdalensis) transmits a Blueberry sharpnosed leafhopper mycoplasma (virus-like pathogen) that Monitoring and Management causes blueberry stunt disease (Figures Monitor weekly using yellow sticky boards between blueberry plants beginning May 1. 12-19a and b). Refer to Chapter 11 for Fruitworm sprays usually control the first generation of leafhopper feeding. information on disease symptoms and In late summer, scout for symptoms of blueberry stunt disease and rogue out the diseased management. This disease appears to be plants. more detrimental in the northernmost Remove wild blueberry. Select resistant cultivars if leafhoppers are problematic: V. vergatum Reade, V. crassifolium regions of the Midwest. subsp. crassifolium Andrews, V. elliottii Chapman, V. staminium L., and V. arboretum Marshall. Adults (Figure 12-19b) are active from mid-May to mid-November with peaks in mid-June, mid-August, and mid-October. References Other Resources Brandhorst-Hubbard, J.L., K.L. Flanders, Michigan Blueberry Facts http://www. and A.G. Appel. 2001. Oviposition site blueberries.msu.edu. and food preference of the green June Michigan State University IPM Scouting beetle (Coleoptera: Scarabaeidae). J. Guide http://blueberries.msu.edu/ Econ. Entomol. 94: 628-633. publications. Jenkins, P., A. Schilder, R. Isaacs, E. Hanson, G. Bird, B. Bordelon, and L. Jess. 2008. Pest management strate- gic plan for the North central region blueberry industry. Sponsored by The North Central Regional IPM Grants Program. Johnson, D.T., B.A. Lewis, R.J. Bry- ant, R. Liyanage, J.O. Lay, and M.A. Pszczolkowski. 2009. Attractants for the green June beetle, Cotinis nitida (Coleoptera: Scarabaeidae). J. Econ. Entomol. 102: 2224-2232. Meyer, J.R., and J.R. Ballington. 1990. Resistance of Vaccinium spp, to the leafhopper Scaphytopius magdalensis (Homoptera: Cicadellidae). Ann. En- tomol. Soc. Am. 83: 515-520.

48 Chapter 13 Managing Wildlife Problems in Blueberries

ildlife provides many positive val- Wues to humans, but when it comes Figure 13-1. Bird damage on ripe fruit. Figure 13-2. A double-strand high tensile into conflict with agricultural produc- electric fence is effective for keeping out deer. tion, wildlife has the potential to cause economic losses to producers. A 1998 The second concept to understand are nutritionally stressed. The most effec- USDA APHIS survey conducted in six is that growers cannot simply kill the tive long-term solution for deer feeding major fruit-producing states found that offending animals, since most are pro- is allowance of a judicious legal harvest blueberry producers lost about 4 percent tected by state and federal laws. Further- of female animals (depredation permit) of their crop to wildlife at an estimated more, it takes substantial time to obtain and then put up temporary or permanent cost of $443,000 dollars. Much of this appropriate permits and, as is often the electric fencing. loss can be attributed to physical dam- case, damage is done and crop is har- Electric Fencing. Much research has age by deer and feeding by birds (Figure vested before hunting permits arrive. shown that a single or double strand of 13-1), particularly blackbirds, starlings, Finally, it is important to think about high-tensile electric fence (Figure 13-2) robins, crows, and ravens. The survey the economics of short-term control ef- can be very effective at keeping deer out also revealed that producers use pyro- forts (such as repellents) versus long-term of production fields (Figure 13-2). The technics (fireworks), frightening devices, solutions (such as fencing or netting). It key to success in using this system is to fences, repellents, and flagging as the is usually cheaper and more effective ensure that chargers produce enough most common methods to alleviate (in the long term) to keep the animals electricity to give sufficient shocks to wildlife damage. This chapter discusses away from production fields, rather than intruding animals. Fences should be kept the most effective management options testing various solutions after problems clear of all weedy growth to ensure that for deer and bird problems. While other begin. For example, methyl anthranilate, vegetation does not ground the system. animals, such as voles, can cause damage, a bird repellent, costs about $25 per acre Electric fencing is the most cost-effective they will not be discussed; however, this and lasts for 10 to 14 days. However, the fencing solution available. If smaller information can be obtained from local repellent needs to be reapplied after each animals, such as rabbits, raccoons, or county Extension agents or fruit produc- rain or heavy dew. Even then, as some re- opossums are a problem, this fence can tion specialists. search has shown, it does not completely be adapted to a two-wire system where General Principles Relating repel birds. Furthermore, some producers one wire is about 2 inches from the to Control of Wildlife Pests have noticed off-flavored berries caused ground and the second wire is 8 inches by repellant residues. On the other hand, to 10 inches above the ground. The two- One of the most important concepts the cost of a high quality netting system wire system prevents smaller animals to understand when managing wildlife can cost $2,300 per acre, with additional from entering under, through, or over the pests is that these problems are sub- labor costs of approximately $500 to $600 fence. stantially easier to solve before wildlife per acre per year to hang and later remove Producers can also erect more per- become habituated to feeding on fruit or netting. Producers should critically manent electric fencing using pressure- plants. Once a feeding pattern has been evaluate each situation and construct a treated posts that have life-expectancies developed, it is difficult to solve without cost-benefit analysis for each technique. of 35 to 40 years. They are powered by large expenditures of time and money. high voltage, low impedance chargers For example, growers located near deer Deer (New Zealand style) capable of charging habitats are most likely going to experi- White-tailed deer typically do not kill 5,000 feet of fence per unit. An additional ence damage at some point. It is more blueberry plants, but instead browse on benefit is that they have a reduced suscep- effective to develop a plan for dealing buds and shoots, thereby reducing yields. tibility to grounding by vegetation. These with feeding behavior before deer begin Much of this damage occurs during the fences use high-tensile, smooth wire to repeatedly enter production fields and, dormant season, although it can occur (200,000 psi, 12½ gauge). Special acces- thereby, cause economic damage. any time populations are high and deer sories help maintain a 150 to 250-pound

49 Figure 13-3. Deer can be deterred with a Figure 13-4. Dryer sheets are often not ef- Figure 13-5. Noise makers are only partially 6-wire high tensile electric fence. fective for repelling wildlife. effective, as birds quickly become accustomed to the noise. tension, so fences can absorb the impact border collies or blue-heeler dogs to chase Chemical Repellents. Methyl anthra- of running deer and spring back to their animals away from production fields. nilate is an EPA-registered bird repellent original positions. The six-wire vertical However, these dogs must not be pets, that can be used on blueberries, but the high-tensile electric fence design is a require special training, and are often volatility of this compound makes it dif- modification of the Penn State five-wire expensive to purchase and keep. Loud ficult to retain repellency for long periods design (Figure 13-3). The lowest wire sounds, lights, or other deterrents are of time. For best results, apply methyl should be 8 inches above the ground not effective for more than a few days, as anthranilate as large droplets, rather and remaining wires are spaced at 10- animals become accustomed to the noise than as a fine mist. There are no poisons inch intervals. The bottom wire is “hot” or lights. labeled for avian use in blueberry fields. and remaining wires alternate between Sugar sprays have been reported to be ground and hot. Rigid corner assemblies Birds temporarily effective. Many fruit-eating must be installed. Fiberglass battens are Of all the wildlife problems that blue- birds cannot digest table sugar, so these placed at 30-foot intervals along fences berry producers combat, birds appear to birds often avoid sugar-treated berries. to maintain wire spacing. Eight-foot line be the most serious and persistent. Birds This will not affect berry quality, and posts are placed every 60 feet for struc- are highly mobile, can concentrate into humans cannot distinguish between tural support. large flocks, and their flocking behavior the monosaccharide sugars found in Repellents, whether chemical, visual, assists them in quickly locating new food blueberries and disaccharide table sugar. or auditory, are not designed to eliminate sources. It is impossible to completely Applications of a concentrated solution damage, rather reduce it to tolerable prevent birds from causing damage, only of table sugar should be made just as levels. The best chemical repellents can reduce amounts of damage that occurs. fruit begin to ripen to prevent birds from reduce damage by up to 50 percent; dam- Many of the bird species that dam- establishing feeding routines. Reapplica- age is reduced more during the dormant age blueberries are federally protected, tion is required after rain or heavy dew. season compared to the growing season. including the American robin, house There are few commercially available, finch, and northern mockingbird. Oth- EPA-registered repellents available for ers, such as brown-headed cowbird, use on fruit crops. In general, commer- common grackle, red-winged blackbird, cially available repellents have better and European starling, can be destroyed efficacy than do home remedies, such as with appropriate permits from the U.S. human hair, soap, dryer sheets (Figure Fish and Wildlife Service. Receiving a 13-4), animal droppings, or urine, etc. permit has become more difficult, as Furthermore, most repellents last from rusty blackbirds, a species that is seri- 1 to 6 days and must be reapplied. They ously declining and protected, can often are often not effective once the animals be found intermingling with grackles, become familiar with them, which can cowbirds, and starlings. While many of occur rather quickly. The best way to these birds are protected by various fed- use these products is to treat plants be- eral laws, growers are allowed to frighten fore animals become used to feeding on or harass them as long as none are killed them. Some producers use well-trained or physically harmed. Figure 13-6. Bird scaring device are only effective until birds become accustomed to the noise.

50 Figure 13-7. Scary-eye balloon devices Figure 13-8. Bird netting that covers entire Figure 13-9. Small growers may hang bird should be used in combination with other plantings can be costly yet effective. netting down single rows because it is easier deterrent methods. to maneuver.

Noise Repellents. The use of hazing or The key to successful use of loud or cables are suspended from poles at loud noises such as fireworks, explod- noises is to move sources of sound fre- the ends of each row and often within ing shells, gas-fired cannons (Figure quently during the day to prevent birds rows. Nets are then rolled out along these 13-5), and distress calls (Figure 13-6) are from adapting to them. Ideally, growers wires either over entire plantings (Figure generally not effective when used alone should use multiple cannons in combi- 13-8) or individual rows (Figure 13-9). because birds quickly grow accustomed nation with multiple firing screamers, Netting is secured to the ground so that to them. However, when used in combi- distress tape calls, and visual deterrents, birds, such as wild turkeys, cannot enter nation with one another and with the use simultaneously. While this is often not underneath. During the remainder of the of stationary objects (such as the scary- physically possible, it is usually more cost year, nets should be re-rolled and stored eye man or balloon, Figure 13-7) these effective than purchase of netting. (Figure 13-10). Draping netting over techniques can help reduce damage for Netting. Recent restrictions on toxi- plants without supports is not effective a few days until crops can be harvested. cants (poisons), pyrotechnics (bird (Figure 13-11). Overall, if the netting can Because the effective range of decoys bangers), and repellents, leave netting as be kept from touching plants, it provides such as a scary-eye balloon is about 12 the only practical alternative to manage- better control of bird pests (Figure 13- feet, a large number of these products are ment of bird problems in blueberry fields. 11). However, if birds learn to peck holes required for efficacy. Use of bird bangers Unfortunately, netting is expensive, time- through netting, heavier and stiffer bird now requires an ATF federal explosive consuming, and difficult to work around netting can be stitched in around these permit that costs $100, renewable every during harvest. locations. Netting may not be practical 3 years for $50. The use of siren screamers One-quarter-inch plastic nets are for large fields and may interfere with does not require this permit, but they are commonly used for small fields. Wire machine harvesting. generally not as effective as bird bangers.

Figure 13-10. Bird netting should be Figure 13-11. Draping netting over plants Figure 13-12. If bird netting comes in direct stowed after harvest to prevent tears and to will not prevent birds from feeding. contact with plants, birds can feed on any ease operations. berries that are on within reach.

51 Chapter 14 Weeds often establish in areas of small weed, however, may need to be dug blueberry plantings where: up and replanted so that it can grow large Weed • Growth conditions are less favorable enough for positive identification. Once • Edges of fields weeds are correctly identified, growers Management • Near blueberry plants should focus on understanding the best methods for management. In order to produce the best blueberry Annual weeds are those that grow from crop possible, growers must learn to ef- seed and then flower and set seed within he main objective of a weed manage- fectively manage weeds. Tment program should be to encour- 12 months. Annual weeds are easiest age a healthy planting that will lead to Weed Identification to manage soon after emergence. They productive, profitable, and sustainable The first step in a successful weed should be eliminated before setting seed, plantings for many years. Weeds should management program is proper iden- which can prevent subsequent infesta- be managed in blueberry plantings in tification. In addition, understanding tions. Summer annual weeds germinate order to decrease competition for water how weeds grow and reproduce, along early in the year and then mature and die and nutrients (Figure 14-1), remove alter- with understanding different means of during summer. Winter annuals germinate hosts for some pests and pathogens, management, increase the likelihood nate in autumn and grow until weather reduce competition for pollinating bees, of success for blueberry growers. For turns cold. They then become dormant improve ease-of-harvest, and to promote example, annual weeds require different until the weather warms the following attractiveness of plantings for pick-your- spring, after which they flower and die. management strategies than perennials, Perennial weeds own customers (Figure 14-2). and grasses are managed differently than survive for multiple The term “weed” has many definitions, broadleaf weeds. years. They can grow and become estab- but simply, a weed is a plant that enters There are several online resources for lished in new areas from seed (Figure habitats occupied by mankind and is weed identification through university 14-3); however, they often reproduce and potentially able to suppress or displace Extension services, as well as through spread through overwintering structures resident plant populations that are de- various weed science society websites. such as tubers, stolons, rhizomes, and liberately cultivated or are of ecological The USDA Plants Database (http:// buds, as well. In order to effectively man- or aesthetic interest. In blueberry plant- plants.USDA.gov) is also useful for weed age perennial weeds, growers should ings, any plants other than blueberry are identification materials. Print resources eliminate or kill underground portions of considered weeds. can be obtained through booksellers as weeds so that they cannot regrow. Other Weeds may have some of the following well. County Extension agents can also than newly germinating perennials, most common characteristics: assist with weed identification or provide perennial grasses and some broadleaf pe- • High reproductive output helpful materials. rennials are best controlled during early • More than one means of reproduction When soliciting assistance in weed spring after regrowth starts. Growers • Ability to withstand environmental identification, it is helpful to have access should not attempt to eradicate weeds extremes such as acidity and drought to a digital camera. With a good quality too early in spring, however. Plants are • Efficient use of limited resources photo, Extension agents or specialists most vulnerable when reserves in roots often can identify weeds using digital have been exhausted. Broadleaf peren- correspondence. A rare weed or very nials tend to be sensitive to herbicides just before blooming, and both perennial

Figure 14-1. Competition from weeds can reduce water and nutri- Figure 14-2. Unsightly, weedy plantings can discourage pick-your- ents available to young plants. own customers.

52 Figure 14-3. Perennial weeds are more difficult to control than an- Figure 14-4. Organic producers often rely on cultural practices as nual weeds. the primary component of their weed management programs. grasses and perennial broadleaf weeds the likelihood of future weed epidemics. One of the most effective cultural may also be controlled in autumn when Avoid planting in areas that are known means of weed control is through sup- plant sugars are being sent to the root to be infested or areas in which weeds pression of weeds using mulch. Blueberry system for storage. establish due to spread by wind patterns, plants benefit from the annual addition Biennial weeds have a two-year life irrigation water, or flooding. of decomposed, organic mulches such cycle. They often do not mature because Scouting. Detection is another major as wood chips. An annual layer of 1 to effective management measures targeted component of a weed management plan. 2 inches of mulch can be effective in toward annuals often manages biennials, While harvesting or other routine main- smothering new weeds or preventing as well. These weeds produce foliage the tenance, growers should take notes on weed seed germination. Woven plastic first year, enter a dormant period, and weed presence and emergence. A pocket- mulches that allow water penetration can then flower and die the second year. sized notebook is useful. Remember: it is also successfully suppress weeds. Hand easier to manage young weeds than older, hoeing and manual removal can be effec- Integrated Weed established weeds, particularly perennial tive, particularly when coupled with the Management Strategies types. Record any instances of herbicide use of organic mulches; weeds growing Prevention is one of the first steps to a failure. There has been a recent increase through mulch tend to be shallow-rooted successful weed management program, in frequency of herbicide-resistant weeds. and fairly easily removed. Mechanical especially for new blueberry plantings. Thus, by noting where previously suc- cultivation can be difficult because blue- The easiest weeds to manage are those cessful herbicide treatments have failed, berry roots are shallow and often grow that never become established. If grow- it is possible to identify early signs of into the same root zone as weeds. ers eliminate perennial weeds prior to herbicide resistance. Herbicides are an important part of establishment of plantings, fewer weeds Suppression is a component of weed weed management programs in most are likely to become problematic. Blue- management that many growers turn to plantings. However, only specific her- berries are perennial crops, so established first. This component includes cultural, bicides are labeled for use in blueberry. weeds in blueberry plantings are often mechanical, and chemical means of man- Herbicide labels are legal documents present for many years. Thus some useful aging weed growth. that provide the information needed for weed management options, such as some Cultural methods include site selection, managing target weeds without harming herbicides and summer fallow, cannot be crop-weed competition, and suppression plants. Read and understand herbicide employed as weed management tools. using mulch. Crop rotation is used as a labels before use; they indicate targeted Therefore, managing weeds during the cultural means of weed control in many weeds, as well as the appropriate rate and site establishment phase is critical. annual crops, but it is not practical for timing. Plant age restrictions are often Prevention includes elimination of blueberry plantings. Blueberries require included on the label, as well. overwintering structures such as sto- an acid soil which limits opportunities Pre-emergent herbicides (PRE) suc- lons, tubers, and rhizomes. Effective for site selection, as many soils through- cessfully suppress weed emergence when weed management prevents spread of out the Midwest may not be suitable applied to soils before seeds germinate. weeds throughout blueberry plantings. for blueberry production. Crop-weed They tend to be somewhat selective and Maintaining clean fence rows and ditch competition is a strategy that suppresses are more effective on some weeds than lines, cleaning equipment to remove weeds by promoting vigorous, healthy others. However, blueberry plants can weed seeds, and obtaining clean plant- blueberry plant growth though appropri- be sensitive to pre-emergent herbicides. ing stock are also beneficial and reduce ate fertilization, watering, and pest and Some pre-emergent herbicides are safe to disease management (Figure 14-4).

53 use on new plants, whereas others should Post-emergent (POST) herbicides are plying products in bands or concentrated only be applied to blueberries that have effective against weeds that overcome patterns (e.g. only blueberry beds and not been established for 2 to 3 years. Check pre-emergent herbicide barriers. These row centers). This is often referred to as labels for specific instructions. products can often be applied as spot the “treated acre” and can result in signifi- Pre-emergent herbicides are usually sprays. Post-emergent herbicides are cant decreases in total herbicide applica- applied in bands under blueberry rows. applied to the foliage of weeds. Some of tions and costs. For best results, follow Treatments times vary from autumn to these products are contact herbicides manufacturers’ application instructions spring, and these treatment times are that only affect plant parts that were regarding rates, additives, soil type, soil indicated on labels. Weed seedlings die directly contacted. Systemic herbicides, moisture conditions, weed growth stage, as they grow through herbicide barriers on the other hand, are absorbed through environmental conditions, and product established in soils. Therefore, growers leaves and stems and move to other plant limitations. should not disturb soil barriers (such as parts (e.g. from foliage to roots). They Every weed management program through cultivation) after application are effective against established peren- should consider herbicide resistance. of pre-emergent herbicides. In addition, nial weeds. Finally, some post-emergent There are a number of different classes frequent irrigation or heavy rain may herbicides are selective and may be effec- (i.e. chemistries or HRAC groups) of move herbicides through soils, below tive only on grasses, or only on broadleaf herbicides that are labeled for blueber- levels where weed seeds reside. More- weeds. Others are non-selective and are ries. Rotation from one class to another is over, pre-emergent herbicides vary in effective against a broad spectrum of important for reducing risk of herbicide- levels of persistence in soil, and control weeds. resistance. Herbicide classes are indi- periods range from a few weeks to several Herbicide rates listed on labels are cated by a number on fronts of labels. months. recommended for broadcast applications across entire fields. Reduce amounts ap-

Photo credits

Chapter 1: Erik Draper, The Ohio State University

Chapter 2: Gary Gao, The Ohio State University

Chapter 3: Gary Gao, The Ohio State University: 1abc, 2, growth stages 10-12; Mark Longstroth, Michigan State University: 3, growth stages 1-9

Chapter 4: Gary Gao, The Ohio State University: 1, 2; Nicole Ward, University of Ken- tucky: 3

Chapter 5: Gary Gao, The Ohio State University

Chapter 6: Gary Gao, The Ohio State University: 1-3, 5-7; Jim Chatfield, The Ohio State University: 4

Chapter 7: Gary Gao, The Ohio State University

Chapter 8: John Strang, University of Kentucky: 1, 2, 5; Gary Gao, The Ohio State University: 3, 4

Chapter 9: Patrick Byers, University of Missouri: 1, 2abc, 5-8; Dwight Wolfe, University of Kentucky: 3, 4

Chapter 10: Gary Gao, The Ohio State University: 1-5, 7ab; Eric Hanson, Michigan State University: 6

Chapter 11: Michigan State University: 1, 3ab, 7, 9b, 10, 11, 17c, 18-20, 22ab; Gerald Holmes, Valent USA Corp, Bugwood.org: 2a; Gary Gao, The Ohio State University: 2b; W. Cline, North Carolina State University: 4a; Annemiek Schilder, Michigan State Uni- versity: 4b, 8, 12, 13, 14d, 15ab; Mary Ann Hansen, VPI, Bugwood.org: 5; John Strang, University of Kentucky: 6, 16; Bruce Watt, University of Maine: 9a; University of Georgia Plant Pathology Archives, Bugwood.org: 14abc; North Carolina State Extension: 14e; Mark Longstroth, Michigan State University: 17ab; Nicole Ward, University of Ken- tucky: 21

Chapter 12: Donn Johnson, University Of Arkansas: 1a, 9abc, 10c, 11abc, 12abc, 17b; Roger Schmidt, University of Wisconsin, Madison, Bugwood.org: 1b; University of Florida Institute of Food and Agricultural Sciences: 2abc; Robert Anderson, USDA FS, Bugwood.org: 3a; Ric Bessin, University of Kentucky: 3b; Rufus Isaacs, Michigan State University: 4ac, 5bc, 6b, 7b, 10b, 14, 16ab, 17a, 18; Soo-Hoon Kim, University Of Arkan- sas: 3c, 7c; Jerry Payne, USDA ARS, Bugwood.org: 4b, 5a, 19b; Gevork Arakelian, Los Angeles County Department of Agricultural Commissioner/Weights and Measures: 6a; E. Levine, The Ohio State University, Bugwood.org: 7a; WonGun Kim, BugGuide: 8; David Cappaert, Michigan State University, Bugwood.org: 10a; Clinton Trammel, Uni- versity Of Arkansas: 13ab; Alan Eaton, University of New Hampshire: 15abcd; Michigan State University: 19a

Chapter 13: Gary Gao, The Ohio State University: 1, 3-12; John Strang, University of Kentucky: 2

Chapter 14: Gary Gao, The Ohio State University

Educational programs of Kentucky Cooperative Extension serve all people regardless of race, color, age, sex, religion, disability, or national origin. Issued in furtherance of Cooperative Extension work, Acts of May 8 and June 30, 1914, in cooperation with the U.S. Department of Agriculture, M. Scott Smith, Director of Cooperative Extension Programs, University of Kentucky College of Agriculture, Food and Environment, Lexington, and Kentucky State University, Frankfort. Copyright © 2013 for materials developed by Univer- sity of Kentucky Cooperative Extension. This publication may be reproduced in portions or its entirety for educational or nonprofit purposes only. Permitted users shall give credit to the author(s) and include this copyright notice. Publications are also available on the World Wide Web at www.ca.uky.edu. Issued 7-2013