Fruit and Vegetable Crops C a T E G O R

C Fruit and A Vegetable T Crops E G O R Y

Pesticide Safety Education Program, Ohio State University Extension 57 Vegetable & Fruit Insecticide News for 2016-2017 Celeste Welty Department of Entomology, Ohio State University Extension New products: • Omega 500F (fluazinam) is primarily a fungicide but it also kills spider mites, for use on apples (28-day PHI). Made by Syngenta. Products with re-established registration: • Closer SC (sulfoxaflor, in IRAC group 4C, the sulfoximines): registration reestablished 10/14/2016. Was registered May 2013, use was suspended in Sept. 2015, all uses cancelled on 11/12/2015. Now for use on pome fruit, stone fruit, grapes, brassica vegetables, fruiting vegetables, leafy vegetables, leaves of root and tuber crops, for control of plant bugs, aphids, leafhoppers, whiteflies. Former label had strawberries and cucurbits but these are not on the new label. Can not be used until after petal-fall on fruit crops. Made by Dow. • Transform WG (sulfoxaflor): registration reestablished 10/14/2016. Had been registered May 2013, but use was suspended in Sept. 2015, then all uses cancelled on 11/12/2015. For use on potatoes, root and tuber crops (radish, celeriac, beet, carrot), and beans, for control of aphids, leafhoppers, plant bugs, whiteflies. Made by Dow. Products with registration expanded to additional crops: • Sivanto Prime (flupyradifurone, in IRAC group 4D; 1.67 lb AI/gal): foliar use will be allowed on stone fruit and caneberries. Soil application will be allowed on Brassica crops and leafy vegetables. From Bayer. Announced September 2016; new label not yet available but coming in 2017. Product consolidations or renamings: • Sivanto Prime (flupyradifurone, in IRAC group 4D; 1.67 lb AI/gal) has replaced Sivanto 200SL (1.67 lb AI/gal), for systemic control of leafhoppers, aphids, whiteflies, squash bug, potato beetle, thrips, pear psylla, San Jose scale, blueberry maggot, mealybug on apples, pears, grape, blueberry, strawberry, Brassicas, cucurbits, fruiting veg, leafy veg, legumes, root veg, tuber/corm veg, hops. From Bayer. Registered January 2015. Stone fruit and caneberries added Sept. 2016. • Portal XLO (0.4EC) has replaced Portal (0.4EC). For control of two-spotted spider mite, European red mite, broad mite, cyclamen mite, tomato russet mite, pear rust mite, pear psylla, leafhoppers, whiteflies. Peaches, potato, beans, and cucumbers are now on main label, no longer on supplemental labels. Also for use on pome fruit, grapes, strawberries, hops, fruiting veg, melons, mint. Made by Nichino. Registration cancellations or deletions: • Belt SC (flubendiamide) and the former Synapse WG (flubendiamide), made by Dow, and Tourismo (flubendiamide + buprofezin), made by Nichino: cancelled August 2016. Distributors allowed to sell remaining inventory. Growers permitted to use product consistent with label use directions. • Thionex, Thiodan (endosulfan): No longer for use on any crop; final use allowed was strawberries (perennial) which ended on 7/31/2016. Uses on all other crops have been phased out over the previous 4 years. Take all remaining product to ODA organized pesticide disposal collection site. • Calypso 4F (thiacloprid): voluntary cancellation was announced by Bayer on 12/13/2013; State registrations are being phased out; is still registered in Ohio for 2017. • Carzol SP (formetanate hydrochloride) is being deleted from our spray guides; its use now restricted to nectarines in the Pacific NW. • Applaud (buprofezin), an insect growth regulator, is being deleted from our spray guide for grapes; it still exists but not registered in Ohio or most other northern States. Made by Nichino America. • Courier SC (buprofezin), an insect growth regulator, is being deleted from our spray guides; it still exists and is registered in Ohio but not in most other northern States that share our spray guide. For use on strawberries, beans, Brassica, cucurbits, fruiting veg., leafy veg. Made by Nichino America. New pests: no pests brand new to Ohio this year, but three continue to spread to new areas within Ohio: • Spotted wing drosophila: on raspberries, blackberries, blueberries. Small worms in ripening fruit. • Brown marmorated stink bug: on peach, apple, raspberry, sweet corn, pepper, tomato. Causes blotches on surface of fruit and corky brown tissue beneath surface; deforms kernels, seeds. • Western bean cutworm: on sweet corn. Similar to corn earworm but with many worms per ear. Old pests: • Two-spotted spider mite: causing problems on many crops. See summary of miticide choices.

60 Pesticide Safety Education Program, Ohio State University Extension Summary of Vegetable & Fruit Insecticide Changes, 2011-2015 (not including pre-mixes)

NEW REGISTRATIONS: herbs and/or mints cucurbits, strawberries sweet corn (none) Closer (11/2015) (none) asparagus apple, blueberry, pepper, potato, tomato, pepper, & eggplant (none) pumpkin, sweet corn, tomato, Closer (5/2013; 10/2016) strawberries winter squash Sivanto (1/2015) Sivanto (1/2015) Endosulfan, Thionex Exirel (1/2014) Nealta (1/2014) (7/31/2015) Verimark (1/2014) Beleaf (2013) apple, pear, cherry, parsley tomato only brambles /caneberries Guthion (9/30/2013) Nealta (1/2014) Sivanto (9/2016) pear cucurbits blueberries Endosulfan, Thionex Sivanto (1/2015) Sivanto (1/2015) (7/31/2013) Exirel (1/2014) Exirel (1/2014) peach, plum, cherry, strawberry Verimark (1/2014) grapes (annual), cabbage, kale, cukes, Brassica head, stem & leafy Closer (5/2013; 10/2016) melons, summer squash, Closer (5/2013; 10/2016) Sivanto (1/2015) lettuce Hero (10/2015) Nealta (1/2014) Endosulfan, Thionex Sivanto (1/2015) Scorpion (2013) (7/31/2012) Exirel (1/2014) apples & pears Verimark (1/2014) Closer (5/2013; 10/2016) beans & peas Sivanto (1/2015) Sivanto (1/2015) Nealta (1/2014) beans only Exirel (1/2014) Transform (5/2013; 10/2016) Madex HP (8/2013) root veg (radish, beets, carrot) peach, plum, & cherry Transform (5/2013; 10/2016) Closer (5/2013; 10/2016) Sivanto (1/2015) Sivanto (9/2016) Apta (4/2014) potato Exirel (1/2014) Transform (5/2013; 10/2016) Madex HP (4/2013) Sivanto (1/2015) Portal (2013) Torac (1/2014) Calypso (4/2013) Verimark (1/2014) Scorpion (2013) onions Venom (2012) Exirel (1/2014) Movento (2013) CANCELLATIONS: Scorpion (2013) pome fruit, stone fruit, grape, Venom (2012) strawberry, sweet corn, lettuces, endive, spinach, Brassica, fruiting veg, leafy veg, parsley (leafy veg.) legume veg, cucurbits Closer (5/2013; 10/2016) Belt (8/2016) Sivanto (1/2015) pome fruit, stone fruit, grape Torac (1/2014) Tourismo (8/2016) Exirel (1/2014) strawberry (perennial) Verimark (1/2014) Endosulfan, Thionex (7/31/2016) Pesticide Safety Education Program, Ohio State University Extension 61 Summary of products for control of spider mites. Table 1: fruit crops and hops. Table 2: vegetable crops. Table 1. Products for spider mite control on specified fruit crops and hops. Product name & Use Pre-harvest interval, by crop common name Hops Straw- Brambles Blueber- Grape Apple Peach berry ry Acramite 50WS or 4SC general 14 days 1 day 1 day not 14 days 7 days 3 days (bifenazate) registered Apollo (clofentezine) general not not not not 21 days 45 days 21 days registered registered registered registered Envidor (spirodiclofen) general 14 days not not not 14 days 7 days 7 days registered registered registered Kanemite (acequinocyl) general 7 days not not not not 14 days not registered registered registered registered registered Nealta (cyflumetofen) general not 1 day not not 14 days 7 days not registered registered registered registered Nexter (pyridaben) general not not not not 7 days 25 days 7 days registered registered registered registered Onager (hexythiazox) general not not not not 7 days 28 days 7 days registered registered registered registered Portal 0.4EC or FujiMite general 15 days 1 day not not 14 days 14 days 7 days 5EC (fenpyroximate) registered registered Savey (hexythiazox) general up to burr 3 days 3 days not not 28 days 28 days registered registered Zeal 72WDG or 72WSP general 7 days 1 day 0 days not 14 days 14 days 7 days (etoxazole) registered Agri-Mek 0.7 SC or restricted 28 days 3 days 7 days not 28 days 28 days 21 days 0.15EC (abamectin) registered MSR (Metasystox-R) 2EC restricted not not not not non- non- non- (oxydemeton-methyl) registered registered registered registered bearing bearing bearing only only only Vydate L 2WSL (oxamyl) restricted not not not not not 14 days non- registered registered registered registered registered bearing only - Celeste Welty, Extension Entomologist, Ohio State University, 7/28/2016.

62 Pesticide Safety Education Program, Ohio State University Extension Table 2. Products for spider mite control on specified vegetable crops.

Product name & Use Pre-harvest interval, by crop common name Beans Melons Cucum- Squash, Tomato Pepper Egg- Sweet bers pump- plant corn kins Acramite 50WS or general 3 days 3 days 3 days 3 days 3 days 3 days 3 days not 4SC (bifenazate) registered Dimethoate 4EC general; 0 days 3 daysa not not 7 daysa 0 daysa not not (dimethoate) not in registered registered registered registered greenhouse Dicofol 4E (dicofol) general 21 days not 2 days 2 days 2 days 2 days not not registered registered registered Oberon 2SC (spi- general not 7 days 7 days 7 days 1 day 1 day 1 day 5 days romesifen) registered Onager (hexythiazox) general not not not not 1 day 1 day 1 day not registered registered registered registered (green- registered house) Portal 0.4EC or general 1 day 3 days 1 day not 1 day 1 day 1 day not FujiMite 5EC (fenpy- registered registered roximate) Zeal 72WDG or general not 7 days 7 days 7 days not not not not 72WSP (etoxazole) registered registered registered registered registered Agri-Mek 0.7 SC or restricted 7 days 7 days 7 days 7 days 7 daysb 7 days 7 days 7 days 0.15EC (abamectin) MSR (Meta- restricted not 14 days 14 days 14 days not not not not systox-R) 2EC registered registered registered registered registered (oxydemeton-methyl) Vydate L 2WSL restricted not 1 daya 1 daya 1 daya 3 daysa 7 daysa 1 day not (oxamyl) registered registered a Product registered for use on this crop but mites not on list of target pests for this crop, however mites listed as target pest on other crops. b 7 days outdoors, or 1 day for commercial greenhouse tomatoes.

- Celeste Welty, Extension Entomologist, Ohio State University, 7/28/2016.

Pesticide Safety Education Program, Ohio State University Extension 63 Scab of Apple SCAB OF APPLE PLPATH-FRU-23 Melanie L. Lewis Ivey, Michael A. Ellis College of Food, Agricultural, and Environmental Sciences, Department of Plant Pathology Department of Plant Pathology, Ohio State University Extension Scab of Apple Melanie L. Lewis Ivey, Assistant Professor, Department of Plant Pathology, The Ohio State University-Ohio Agricultural Research and Development Center, Wooster, OH. Michael A. Ellis, Professor Emeritus, Department of Plant Pathology, The Ohio State University-Ohio Agricultural Research and Development Center, Wooster, OH.

Apple scab is one of the most serious diseases of apple worldwide. In addition to apples, crabapples and mountain ash are also susceptible to apple scab disease. Apple scab is caused by the fungus, Venturia inaequalis. Both the leaves and fruit can be affected. Infected leaves may drop prematurely resulting in unsightly trees, with poor fruit production. This early defoliation may weaken trees and make them more susceptible to winter injury or other pests. Diseased fruits are blemished and often severely deformed and may also drop early.

Figure 2. Apple scab lesions on fruit.

Symptoms first appear as spots (lesions) on the lower leaf surface, the side of the leaf that is first exposed to the fungal spores as the buds open. At Figure 1. Apple scab lesions on apple leaves. first, the lesions are small, velvety, olive green in color, and have unclear margins (Figure 1-left). On some Disease Development and Symptoms crabapples, infections may be reddish in color. The Disease development is favored by wet, cool weather fungus produces a second type of spore (conidium) in that generally occurs in spring and early summer. The these lesions. These spores are carried and spread by fungus survives the winter on diseased leaves that splashing rain to other leaves and fruits and new have fallen under the tree the previous year. In the infections occur. As the spots age, the infections spring, when buds are beginning to develop, the become darker with more distinct margins (Figure 1- fungus produces millions of spores (ascospores). right). Lesions may appear more numerous closer to These spores are released into the air during rainy the mid-vein of the leaf. If heavily infected, the leaf periods in April, May and June. They are then carried becomes distorted and drops early in the summer. by the wind to young leaves, flower parts and fruits Trees of highly susceptible varieties may be severely and infection is initiated. defoliated by mid to late summer.

ohioline.osu.edu/factsheet/plpath-fru-23 64 Pesticide Safety Education Program, Ohio State University Extension Scab of Apple—page 2

Fruit symptoms are similar to those found on Cultural practices leaves. However, the margins of the spots are Rake and destroy fallen leaves below apple and often more distinct on the fruit (Figure 2) than crabapple trees in the fall (Figure 3). This will on the leaves. Fruit may also be deformed. dramatically reduce the number of spores that can start the disease cycle (Figure 4) over again the following Apple Scab Management spring. Leaves can also be chopped with a mulching Apple scab can be successfully managed by lawn mower or flail mower but this practice should be integrating resistant varieties, cultural practices, coupled with two or three applications of 5% urea to and chemical or biological control. fall foliage. Urea applications increase leaf Variety selection decomposition. Planting resistant or scab immune apple varieties For new plantings, select a site that gets direct is the ideal method for managing scab. Backyard sun for at least eight hours and space trees so that air and organic growers are strongly encouraged to can move easily through the tree canopies and orchard. plant resistant varieties in order to reduce or Tree spacing will depend on the type of apple tree eliminate the need for fungicide applications. (dwarf vs. standard) and trellising system. Prune trees There are numerous apple varieties with yearly to open the canopy and promote leaf drying. complete resistance or moderate resistance to Table 1. Varieties with resistance to apple scab. apple scab (Table 1). All other varieties, including most commercially grown varieties are Apple varieties with complete resistance to scab susceptible to scab; however, they differ in their Crimson Crisp Novamac degree of susceptibility. Scab resistant varieties Crimson Gold Priscilla vary in susceptibility to early-season diseases and Enterprise Pristine all are susceptible to summer diseases Freedom Redfree (J.Beckerman, BP-132-W). Galarina Scarlet Prima Goldrush Sir Prize Jonafree Sundance Liberty Williams Pride Nova Easygro Apple varieties with moderate resistance to scab Adam’s Permain NJ90 Ashmead’s Kernel Suncrisp Haralson Yellow Transparent Honey Crisp Apple varieties with low resistance to scab Akane Murray Belmac Nova Spy Britegold Paulared Figure 3. Fallen leaves should be raked and in Florina (Querina) Pinova (Corrail) the fall to reduce new infections in the spring. Grimes Golden Redfree Honey Gold Runkel Macfree Wolf River Moira

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Chemical and biological control Where resistance to scab is not present, the application of fungicides is the primary method to manage apple scab. Organic and backyard growers can use biocontrol products to suppress disease development but these products should be used in combination with resistant varieties to achieve maximum control. Proper timing of fungicides is critical for effective control of apple scab. Applications should begin early in the season when the first green tips begin to emerge and continue on a 7- to 10-day schedule through out the season. Early applications will reduce the number of seasonal sprays needed to manage apple scab and will increase fruit production and quality. Commercial growers can consult the Figure 4. Apple scab disease cycle. Image Midwest Fruit Pest Management Guide (Bulletin 506) courtesy of W. Wilcox, Cornell University, NYSAES, for current fungicide recommendations and spray Geneva, NY. schedules. Backyard growers are limited in the number of highly effective fungicides available for apple scab management. Most of the available fungicides are protectants and will need to be applied after heavy rains. For current fungicide recommendations backyard growers can consult the Controlling Diseases and Insects in Home Fruit Plantings (Bulletin 780) guide. Both guides can be obtained from your county extension office or the CFAES Publications online bookstore at estore.osu-extension.org.

Useful References Beckerman,J., Disease Susceptibility of Common Apple Cultivars. Purdue Extension, BP-132-W

The College of Food, Agricultural, and Environmental Sciences and its academic and research departments including, Ohio Agricultural Research and Development Center (OARDC), Agricultural Technical Institute (ATI) and Ohio State University Extension embraces human diversity and is committed to ensuring that all research and related educational programs are available to clientele on a nondiscriminatory basis without regard to age, ancestry, color, disability, gender identity or expression, genetic information, HIV/AIDS status, military status, national origin, race, religion, sex, sexual orientation, or veteran status. This statement is in accordance with United States Civil Rights Laws and the USDA. Bruce McPheron, Ph.D., Vice President for Agricultural Administration & Dean For Deaf and Hard of Hearing, please contact the College of Food, Agricultural, and Environmental Sciences using your preferred communication (e-mail, relay services, or video relay services). Phone 1-800-750-0750 between 8 a.m. and 5 p.m. EST Monday through Friday. Inform the operator to dial 614-292-6891. Copyright © 2014, The Ohio State University

66 Pesticide Safety Education Program, Ohio State University Extension Bitter Rot of Apple Melanie L. Lewis Ivey, Michael A. Ellis PLPATH-FRU-20 DEPARTMENT OF PLANTDepartment PATHOLOGY of Plant Pathology, Ohio State University Extension Bitter Rot of Apple Melanie L. Lewis Ivey, Assistant Professor, Department of Plant Pathology, The Ohio State University-Ohio Agricultural Research and Development Center, Wooster, OH. Michael A. Ellis, Professor Emeritus, Department of Plant Pathology, The Ohio State University-Ohio Agricultural Research and Development Center, Wooster, OH.

Bitter rot is a common fruit rotting disease of apple Symptoms first appear as small, slightly sunken (and pear) that occurs in all states where apples and circular areas that are light to dark brown in color. On pears are grown (Figure 1). Bitter rot is caused by mature fruit these areas may be surrounded by a red the fungi, Colletotrichum gloeosporiodes, C. halo. When environmental conditions are optimal, acutatum and Glomerella cingulata. Colletotrichum the spots can enlarge rapidly and cover the entire fruit gloeosporioides and C. acutatum are the same surface. As the spots enlarge, the fruit rot symptoms pathogenic fungi that cause anthracnose fruit rot on can vary depending on the fungal isolate and the type strawberry and blueberry, ripe rot on grape and of spore that initiates infection. Spots initiated from anthracnose disease on peach. Glomerella cingulata by isolates that only produce conidia (referred to as can also cause a leaf spot and canker on apple, conidial isolates) are sunken and circular with although these forms of the disease are not common concentric rings. Within the rings, copious amounts in Ohio. of conidia are produced in fruiting bodies called acervuli (Figure 2-Top). Under moist, humid conditions, the spore masses appear creamy and are salmon to pink in color. Spots initiated by isolates that produce conidia and ascospores (referred to as perithecial isolates) are usually not sunken and are darker brown in color than spots produced by conidial isolates (Figure 2-Bottom). Within the spots, structures that contain ascopsores (perithecia) form in Figure 1. Bitter rot on apple fruit. black clumps over the surface.

Disease Development and Symptoms Figure 2. Close-ups of bitter rot on Disease development is favored by high temperatures apple fruit. (80-90 degrees F) and high relative humidity (80- 100%); thus the disease is most common in the Top- Sunken lesion southeastern United States. The fungi survive the containing winter in dead wood or mummified fruit that were concentric rings of infected during the previous season. In the spring, acervuli. Photo spores (conidia and/or ascospores) from these courtesy of Jon overwintering sites serve as the primary inoculum Clements, Umass source for new infections. Conidia are spread by Amherst. splashing and wind-blown rain, insects and birds while ascospores are released into the air during rainy Bottom- Dark circular lesion with periods. Fruits are susceptible to infections from brown acervuli petal fall through harvest. scattered on the surface.

Pesticide Safety Education Program, Ohio State University Extension 67 Bitter Rot of Apple—page 2

As spots enlarge, the rot progresses inward towards Chopping dead wood on the ground with a flail-type the core. After making a cross-section of the infected mower will remove most of the bark and increase the fruit a V-shaped, brown watery lesion can be rate of decomposition. Removing and burning observed (Figure 3). This is a key diagnostic feature mummified fruit from trees throughout the growing of bitter rot, which distinguishes it from other season will reduce inoculum levels during the current summer fruit rots (i.e. white rot and black rot). and following season.

Leaf lesions and cankers are uncommon in Ohio. Any practice that helps to maintain trees in a healthy Leaf lesions begin as small, red flecks, which enlarge vigorous condition is critical for controlling the canker to irregular brown spots that are 1/16 to 1/2 inch in phase of bitter rot disease. Cankers generally develop diameter. Severely affected leaves may drop off the only on stressed or weakened trees, especially winter- tree. Cankers are oval, sunken, and often marked injured trees. Prune trees annually and maintain a with zones (zonate). balanced fertility program based on soil and foliar nutrient analyses. Chemical control Fungicides applied from first cover until harvest on a 10-14 day schedule are effective at controlling fruit rot if a good sanitation program is implemented. Fungicides are not effective for controlling the canker phase of the disease on weakened trees. For the most current fungicide recommendations, commercial growers are referred to the Midwest Figure 3. Cross section of bitter rot infected fruit. Fruit Pest Management Guide (previously Bulletin Note the “V” shaped lesion. This characteristic 780). Backyard growers are referred to Bulletin distinguishes bitter rot from white rot and black 780, Controlling Diseases and Insects in Home Fruit rot. Plantings, which is available from your county Extension office or the CFAES Publications online Bitter Rot Management bookstore at estore.osu-extension.org. Bitter rot can be successfully managed by integrating good sanitation practices, cultural practices and chemical control. There are no varieties that are resistant to bitter rot. Sanitation and cultural practices Bitter rot control is dependent on good orchard and tree sanitation. Dead wood, including shoots infected with fire blight, is an important source of inoculum and should be removed from the orchard and burned.

Copyright © 2014, The Ohio State University 68 Pesticide Safety Education Program, Ohio State University Extension Fire Blight of Apples and Pears FIRE BLIGHT OF APPLES AND PEARS PLPATH-FRU-22 Melanie L. Lewis Ivey, Michael A. Ellis College of Food, Agricultural, and Environmental Sciences, Department of Plant Pathology Department of Plant Pathology, Ohio State University Extension Fire Blight of Apples and Pears Melanie L. Lewis Ivey, Assistant Professor, Department of Plant Pathology, The Ohio State University-Ohio Agricultural Research and Development Center, Wooster, OH. Michael A. Ellis, Professor Emeritus, Department of Plant Pathology, The Ohio State University-Ohio Agricultural Research and Development Center, Wooster, OH.

Fire blight is a common and very destructive bacterial disease of apples and pears (Figure 1). The disease is caused by the bacterium Erwinia amylovora, which can infect and cause severe damage to many plants in the rose (Rosaceae) family (Table 1). On apples and pears, the disease can kill blossoms, fruit, shoots, twigs, branches and entire trees. While young trees can be killed in a single season, older trees can survive several years, even with continuous dieback.

Table 1. List of commonly grown plants in Ohio that are susceptible to fire blight. Apple Mountain Ash Blackberry Pyracantha Cotoneaster Quince Crabapple Raspberry Hawthorn Spirea

Disease Development Figure 1. Fire blight damage on an apple tree. Fire blight first appears in the spring when temperatures get above 65 degrees F. Rain, heavy infect an entire orchard. These bacteria multiply dews, and high humidity favor infection. Precise rapidly in the blossom nectar, and spread to the environmental conditions are needed for infection to spurs (blossom bearing twigs), new shoots and occur and as a result disease incidence varies branches, resulting in secondary infections. Shoot considerably from year to year. infections can also occur through wounds created Fire blight bacteria overwinter as cankers in by sucking insects (aphids, leafhoppers or tarnished living tissue on the trunk and main branches and on plant bugs), freeze or frost damage, wind whipping, mummified fruit. Primary infections (Figure 2) are wind driven rain, or hail. Once a shoot is infected initiated during bloom when bacteria are carried from the fire blight bacteria multiply rapidly and droplets the cankers to open flowers by splashing rain, of ooze can be seen within 3 days. Shoots remain pollinating insects (i.e. bees, pollen wasps, flies, ants) highly susceptible to infection until vegetative or during production practices such as pruning. growth ceases and the terminal bud is formed. Relatively few overwintering cankers become active and produce bacteria in the spring, but a single active canker may produce millions of bacteria, enough to

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Symptoms Fire blight symptoms vary depending on the tissue affected and can also vary between pear and apple.

Blossom and Spur Blight Blossom and spur symptoms appear in the spring. Bacteria gain entry into the tree via blossoms and new shoots. Diseased blossoms become water- soaked, wilt and turn brown. Bacteria spread rapidly into other flowers in the cluster and then move down into the spur. Spurs become blighted, turning brown on apples and black on pear (Figure 3). Shoot Blight Shoot blight starts at the growing tips of shoots and moves rapidly down into older portions of the twig. Blighted twigs first appear water-soaked, then turn dark Figure 3. Fire blight on apple blossoms and brown or black. As blighted shoots wilt the twigs bend spurs. at the growing point and resemble a shepherd’s crook or an upside down “J” (Figure 4). Blighted leaves remain Stem Cankers attached to the dead branches throughout the summer. As fire blight bacteria move through blighted twigs During warm and humid weather infected shoots will into the main branches, the bark sometimes cracks ooze droplets of creamy white bacteria. along the margin of the infected area causing a distinct canker (Figure 5). Bark on younger trees becomes water soaked and the cankers have a Blossom Bacteria disseminated infection Blossom-to -blossom dark brown to purple color. Sapwood beneath a by insects, rain and transfer by pollinators pruning canker has a reddish brown appearance (Figure 5) and may be soft to the touch. Cankers can girdle the main branches and trunk causing additional

Active canker Shoot infection dieback. with bacterial ooze Fruit Blight Both apple and pear fruit may be blighted. Rotted Fruit blight areas turn brown to black and become covered with droplets of whitish tan colored bacterial ooze. Fruit remain firm and eventually dry out and

Blossom and shrivel into mummies. Overwintering Shoot and spur blight canker twig blight Rootstock Symptoms Fire blight symptoms on rootstocks usually develop near the graft union. Symptoms are similar to Infections extend into wood and new cankers those of stem cankers. Fire blight infections in are formed rootstocks can rapidly kill the tree by girdling the rootstock. Figure 2. Fire blight disease cycle.

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70 Pesticide Safety Education Program, Ohio State University Extension Fire Blight of Apples and Pears—page 3

Management Infected plant tissue should be taken out of the Fire blight is one of the most difficult diseases of orchard and burned or placed into the trash. apple and pear to manage, and no one procedure will give complete control. Though management is not an easy task, the use of several practices in an integrated manner should result in minimal damage and losses from fire blight. Commercial growers should consider following a recommended chemical spray program for fire blight Chemical sprays for fire blight control are generally not recommended for backyard growers. Instead, backyard growers are encouraged to plant less susceptible varieties and use other nonchemical control measures, some of which are described below. For the most current spray recommendations, commercial growers are referred to Bulletin 506, Midwest Fruit Pest Management Guide, and backyard growers are referred to Bulletin 780, Controlling Diseases and Insects in Home Fruit Plantings. These publications can be obtained from your county Extension office or the CFAES Publications online bookstore at estore.osu- Figure 4. Fire blight on an apple twig. extension.org. Note the curved “Shepherd’s Crook” at the tip of the diseased twigs. Image Management Tactics for Fire Blight courtesy of Marcus McCartney, OSU Select and plant resistant varieties. Planting highly Extension Washington County susceptible varieties makes fire blight management extremely difficult. When establishing an orchard Minimize summer pruning of blighted shoots. select and plant apple and pear rootstocks (Table 2) Summer pruning of blighted shoots can slow the and varieties (Table 3) that are less susceptible to fire movement of bacteria in the orchard if done carefully blight. and correctly. However, if proper sanitation practices are not used, bacteria can be inadvertently spread to Prune out fire blight cankers and blighted twigs. healthy tissue and exacerbate the disease. Pruning of Dormant season (winter) pruning of blighted twigs and blighted shoots should only be done in dry weather, cankers removes fire blight bacteria from the orchard cuts should only be made into healthy tissue that is at so that the bacteria will not be there to start new least 12 to 15 inches below diseased wood, and infections in the spring. Even in orchards without a pruning tools must be sanitized after each cut. Tools known history of fire blight, it is important to look for can be sanitized by dipping them into a 10 percent blighted twigs and cankers and remove them. To bleach solution (1 volume of bleach to 9 volumes of remove blighted twigs, make a clean cut into healthy water) containing a few drops of liquid soap. A new tissue that is at least 4 inches below visibly dead wood. bleach solution should be prepared when the Cankers can be cut out of trunks or large branches by solution appears dirty. Infected plant tissue should be removing dead tissue until healthy tissue is observed. taken out of the orchard and burned or placed into the trash.

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Pesticide Safety Education Program, Ohio State University Extension 71 Fire Blight of Apples and Pears—page 4

streptomycin is applied while the flowers are open. For this reason, streptomycin may need to be applied multiple times until petal fall. Streptomycin can also be applied as a rescue treatment following a severe weather event such as hail, wind driven rain or high winds. Streptomycin is available to backyard gardeners but is not recommended due to the Useful References risk of the bacteria becoming resistant to the antibiotic if it is not used properly. To reduce the risk of antibiotic resistance: • Use the recommended rate on the Figure 5. Fire blight streptomycin label cankers on young apple • Make no more than three to four tree trunks (top) and mature tree branch applications per season (left). Note the reddish • Do not use streptomycin after brown appearance of symptoms have developed the sapwood beneath • Do not use streptomycin for shoot blight the canker on the or canker control mature tree branch. Table 2. Level of fire blight resistance in apple and pear rootstocks S=susceptible; MR=moderately resistant and; R=resistant Follow proper pruning and fertilization practices. Apple Rootstocks Resistance Level Excessive nitrogen fertilizer and heavy pruning will Bud.9* S promote vigorous growth of succulent tissue, which is Bud.118 MR very susceptible to fire blight. Make fertilizer Geneva 11 R applications in early spring or late fall after growth has Geneva 16 R ceased. Never conduct routine pruning (i.e. pruning M.7 R to stimulate growth or shape the tree) at the same M.9* S time as pruning to remove blighted, twigs, shoots or M.26 S cankers. MM.106 MR MM.111 MR Make an early season application of copper. Trees Pear Rootstocks with a history of fire blight should be sprayed with a Bartlett seedling S copper based pesticide to reduce the build-up of Old Home (OH) R bacteria on buds and bark. Copper should be applied Old Home x R at silver tip (when buds are just beginning to swell) to Farmingdale (except green tip and no later than half-inch green (Figure 6). OH x F 51) Quince seedling S Spray streptomycin at bloom. Streptomycin is an *Although Bud.9 and M.9 are susceptible to antibiotic that can kill fire blight bacteria before they fire blight, observations in Ohio indicate that enter the apple tree. The nectaries of the flowers are Bud.9 is less susceptible to rootstock where bacteria enter apple trees, so it is critical that infection by fire blight bacteria than M.9.

ohioline.osu.edu/factsheet/plpath-fru-22

72 Pesticide Safety Education Program, Ohio State University Extension Fire Blight of Apples and Pears—page 5

The biological control product Serenade Garden Table 3. Relative susceptibility of common Defense, which contains beneficial antibiotic apple and pear cultivars to fire blight producing bacteria (Bacillus subtilis), can be used by Highly Moderately Moderately backyard gardeners in place of streptomycin. Like Susceptible Susceptible Resistant streptomycin, Serenade Garden Defense should be applied to open flowers through bloom. Apple Beacon Dutchess Jonafree Apply the plant growth regulator Apogee. Apogee Cortland Empire Melrose (prohexadione-calcium) is a growth inhibitor that Northwestern Fuji Golden Delicious can reduce shoot blight when applied preventatively Greening at 1 to 3 inches of new shoot growth. Apogee will Gala Haralson Nova Easygro not control blossom or spur blight. Orchards with a Granny Smith Jonagold Prima history of fire blight or planted with fire blight Idared Jonamac Priscilla susceptible varieties or rootstocks will benefit the Jonathan Jerseymac Quinte most from an Apogee treatment. Commercial Lodi Liberty Red Delicious growers should contact their county Extension Monroe McIntosh Red Free Educator or fruit tree specialist for guidance on Mutsu Minjon Sir Prize determining if Apogee should be applied in their (Crispin) orchard. Apogee is not recommended for backyard Paulared Northern Spy Pristine growers. Rome Beauty Novamac Liberty Control sucking insects. Sucking insects create Wayne Spartan Goldrush wounds through which fire blight bacteria can Wealthy Honeycrisp Enterprize Yellow enter. These pests should be controlled throughout Braeburn Sundance the growing season. To protect bees, do not apply Transparent Winsap/Staymen Williams insecticides during bloom. Ginger gold strains Pride Pear Aurora Maxine Kieffer Bartlett Seckel Magness Bosc Beurre D’Anjou Moonglow Clapp’s Harrow Favorite Delight Red Bartlett Honeysweet Figure 6. Apple buds at the silver tip (left) and Reimer Red Blake’s Pride early green tip stage (right). Images courtesy of Starkrimson Mark Longstroth, Michigan State University Extension and Dave Schmitt, Rutgers Cooperative Extension.

Pesticide Safety Education Program, Ohio State University Extension 73 Reducing 2,4-D andOHIO Dicamba STATE UNIVERSITY Drift EXTENSIONRisk to Fruits, Vegetables, and Landscape Plants HYG-6105-15 AGRICULTURE AND NATURALDouglas DoohanRESOURCES and Roger FACT Downer SHEET ReducingDepartment 2,4-D of Horticulture and and CropDicamba Science The Ohio Drift State University Risk to OHIO STATE UNIVERSITY EXTENSION Fruits,AGRICULTURE Vegetables AND NATURAL RESOURCES and Landscape FACT SHEET PlantsHYG-6105-15 Douglas J. Doohan and Roger A. Downer, Horticulture and Crop Science

Reducing2,4-D and dicamba are common 2,4-D examples and of a class Dicamba of herbicides known as syntheticDrift auxins. Risk Auxins are naturallyto occurring plant hormones. Synthetic auxins can be used to kill weeds by inducing hormonal effects on sprayed plants. TheseFruits, effects are usually Vegetables characterized by severe distortion and of stems Landscape and leaves. Unintentional applicationPlants of a synthetic auxinDouglas herbicide J. Doohan to aand sensitive Roger A.plant, Downer either, Horticulture through direct and Cropapplication Science or spray drift, often causes severe injury, loss of yield, and even death of the non-target plants. Not all fruits, vegetables and landscape plants are highly sensitive to synthetic auxins, but most will react to exposure in characteristic ways (Figures 1–3). Why2,4-D should and dicamba you be areconcerned common about examples synthetic of a auxinclass ofherbicides? herbicides Simply known because as synthetic 2,4-D auxins. and dicamba Auxins areare naturallylikely to beoccurring used much plant more hormones. extensively Synthetic and auxinsintensively can bethroughout used to kill the weeds Midwest, by inducing starting inhormonal the near effects future. on A littlesprayed history plants. will helpThese to effects put the are elevated usually risk characterized in perspective. by severe 2,4-D distortion is considered of stems to be and the leaves. first modern Unintentional herbicide application and has ofbeen a synthetic in con- tinuousauxin herbicide use on farms, to a sensitive roadsides plant, and either lawns through since the direct late 1940s.application Dicamba or spray was drift,first releasedoften causes as a severecommercial injury, product loss of inyield, the 1960sand even and death continues of the to non-target be used for plants. weed Notcontrol all fruits, in corn, vegetables wheat, pastures and landscape and lawns. plants Unfortunately, are highly sensitivesome older to 2,4-Dsynthetic and auxins,dicamba but formulations most will react were to notoriously exposure inprone characteristic to spray drift ways and (Figures to post-application 1–3). volatilization. This caused unintentionalWhy should damage you be to, concerned and even aboutdeath syntheticof, sensitive auxin crops herbicides? and other Simply plants presentbecause in 2,4-D nearby and fields dicamba and homesteads. are likely to Overbe used time, much lawsuits more and extensively government and intensivelyregulations throughout resulted in thechanges Midwest, to the starting way thesein the herbicidesnear future. were A little used, history and will to physical/chemicalhelp to put the elevated characteristics risk in perspective. of the formulations, 2,4-D is consideredto reduce the to potentialbe the first for modern off-site movement.herbicide and Nevertheless, has been in 2,4-D continuous use on farms, roadsides and lawns since the late 1940s. Dicamba was first released as a commercial product and dicamba have been among the most likely herbicides to be implicated in spray drift cases. For example, survey in the 1960s and continues to be used for weed control in corn, wheat, pastures and lawns. Unfortunately, some older results of state pesticide control officials listed 2,4-D as the herbicide most often involved in pesticide drift incidents 2,4-D and dicamba formulations were notoriously prone to spray drift and to post-application volatilization. This caused (crop damage) every year the survey has been taken (2005 AAPCO Pesticide Drift Enforcement Survey). The same unintentional damage to, and even death of, sensitive crops and other plants present in nearby fields and homesteads. survey lists dicamba as the 3rd most commonly involved in drift incidents for two years in a row. Over time, lawsuits and government regulations resulted in changes to the way these herbicides were used, and to This level of drift occurrence far physical/chemical characteristics of the formulations, to reduce the potential for off-site movement. Nevertheless, 2,4-D outpaces the relative use of these and dicamba have been among the most likely herbicides to be implicated in spray drift cases. For example, survey herbicides: 2,4-D is the 7th most results of state pesticide control officials listed 2,4-D as the herbicide most often involved in pesticide drift incidents commonly applied conventional pes- (crop damage) every year the survey has been taken (2005 AAPCO Pesticide Drift Enforcement Survey). The same ticidesurvey active lists dicamba ingredient as and the dicamba3rd most commonly involved in drift incidents for two years in a row. is notThis even level among of drift the occurrence top 25. This far isoutpaces because the these relative active use ingredients of these areherbicides: toxic to many 2,4-D broadleaf is the 7th plants most at ultra-lowcommonly concentrations; applied conventional hence, pesdrift- damageticide active symptoms ingredient develop and dicamba readily andis not are even easy among to see theand top identify. 25. This is becauseThere are these several active reasons ingredients why theseare toxic herbicides to many are broadleaf being used plants more at byultra-low grain farmers. concentrations; The main hence, reason drift is thatdamage proliferation symptoms of weed develop species readily with highand arelevels easy of toresistance see and toidentify. the most commonlyThere are used several herbicide, reasons glypho why- sate,these isherbicides making are weed being control used more with currentby grain methods farmers. ineffective The main (Figure reason 4). is thatIn proliferation response, of new weed approaches species with tohigh managing levels of resistance resistant to biotypes the most arecommonly being used pursued. herbicide, These glypho new- approachessate, is making currently weed center control on withthe Figure 1.- 2,4-D damage on grapes. current methods ineffective (Figure 4). In response, new approaches to managing resistant biotypes are being pursued. These new extension.osu.edu approaches currently center on the Figure 1.- 2,4-D damage on grapes. agnr.osu.edu

74 Pesticide Safety Education Program, Ohio State University Extension extension.osu.edu agnr.osu.edu Reducing 2,4-D and Dicamba Drift Risk to Fruits, Vegetables and Landscape Plants—page 2

Figure 2. Grape response to simulated drift of dicamba. Figure 3. 2,4-D damage on tomato.

2,4-D-based Dow AgroSciences’ EnlistTM Weed Control System and Monsanto’s dicamba-based Roundup Ready® Xtend Crop System. The EnlistTM system involves genetic modifications to corn and soybeans to produce tolerance to 2,4-D and glyphosate. The Xtend system will provide tolerance to dicamba and glyphosate in soybean. How quickly can you expect increased use of 2,4-D or dicamba in fields near you? It’s difficult to say with certainty but on September 17, 2014, the U.S. Department of Agriculture issued its decision deregulating Dow AgroSciences’ EnlistTM corn and soybean traits in the United States. Following this action Dow AgroSciences’ 2,4-D containing Enlist DuoTM herbicide, the companion herbicide to the EnlistTM traits, was approved by the U.S. Environmental Protection Agency (EPA) on October 15, 2014. The Xtend system is awaiting regulatory approval.

So why should we be concerned? Ohio grain farmers grow more than 4 million acres of soybean and more than 3 million acres of corn, nearly all of which are sprayed with herbicides to control weeds. A consequence of the new genetically modified (GM) crops is that many, perhaps nearly all, of these acres will be sprayed with 2,4-D or dicamba in the future. Not only is use of these herbicides likely to increase, but patterns of use will change as well. A stated benefit of the EnlistTM and the XtendTM weed control systems is they give extended application flexibility before planting, at planting, and after planting. This intended change in the use pattern increases the likelihood that applications to corn and soybeans will coincide with the more susceptible growth stages of sensitive crops and plants such as fruits, vegetables and landscape plants. Changing weather patterns may further impact application timing resulting in applications coinciding with susceptible growth stages of sensitive plants. In 2013 an unprec- edented number of drift damage incidents involving vineyards occurred in Ohio due in part to weather conditions that resulted in burndown herbicide applications coinciding with susceptible growth stages of grapes. Though Figure 4. Glyphosate resistant horseweed in soybeans. (photo courtesy of Mark Loux.) Pesticide Safety Education Program, Ohio State University Extension 75 Reducing 2,4-D and Dicamba Drift Risk to Fruits, Vegetables and Landscape Plants—page 3

vineyard acreage is small compared to row-crop acreage, the fact that vines are a perennial crop, and grape harvests and products have high value, means that a little damage can have large economic consequences.

How is the risk being reduced? Many specialty crop growers fear that these new GM crop technolo- gies and their specialty crops cannot co-exist. However, the perceived risks may not be as high as many people fear. 2,4-D and dicamba have, after all, been used on millions of acres since the 1960s and while drift and volatility have been an issue (Figure 5), the approved use of these products has not resulted in widespread catastrophic damage. Dow AgroSciences, Monsanto and BASF have taken great care to minimize the known negative attri- butes of older 2,4-D and dicamba formulations. Dow AgroSciences has developed Enlist DuoTM that includes a new low-volatility formulation of 2,4-D with minimized drift potential, lower odor, and bet- Figure 5. Schematic showing herbicide vapor drifting into sensitive non-target crop. ter handling characteristics than currently available 2,4-D amine or ester formulations. BASF plans to produce a “technologically advanced” dicamba formulation branded EngeniaTM for use on dicamba-tolerant crops, including soybeans and cotton, that has been formu- lated to provide increased weed control and reduced volatility. Educational and outreach programs to farmers, dealers and commercial applicators (EnlistTM Ahead) to promote and encourage good stewardship of the new system have also been initiated. Risks associated with dicamba will also be reduced through product formulation and stewardship programs. A premix of dicamba and glyphosate herbicide branded as Roundup XtendTM with VaporGripTM technology will be introduced upon regulatory approval of the Roundup Ready® Xtend Crop System. This low-volatility formulation will be labeled for use before, at and after planting.

What spray drift and volatilization are and how to prevent them from happening

Spray drift—The Environmental Protection Agency (EPA) defines spray drift as the movement of pesticide dust or droplets through the air at the time of application or soon thereafter, to any site other than the area intended. As a result of extensive research, the causes and fixes of spray drift are well known and documented. For example, using nozzles and pressures that result in the creation of fine spray droplets, and/or spraying during windy conditions greatly increase the risk of drift. Pesticide labels routinely contain much information on steps that applicators should take to reduce the risk of drift occurring. The instructions on the pesticide label are given to ensure the safe and effective use of pesticides with minimal risk to the environment. Many drift complaints result from application procedures that violate the label instructions.

Volatilization—Volatilization occurs when pesticide surface residues change from a solid or liquid to a gas or vapor after an application of a pesticide has occurred. Once airborne, volatile pesticides can move long distances off site. The potential for a pesticide to volatilize is related to the vapor pressure of the chemicals involved. Pesticides with high vapor pressure are likely to be more volatile than those with low vapor pressure. Pesticides known to have the potential to vaporize carry label statements that warn users of this fact. While there are things that the applicator can control (e.g., nozzle tip, pressure, boom height) to reduce spray droplet or dust drift, vapor drift is dependent upon the weather conditions at the time of application since the likelihood of pesticide volatilization increases as temperature and wind speed increases and if relative humidity is low.

76 Pesticide Safety Education Program, Ohio State University Extension Reducing 2,4-D and Dicamba Drift Risk to Fruits, Vegetables and Landscape Plants—page 4

Despite an applicator’s best intentions, the risk of spray drift occurring is always present, most often as the result of the factors involved that are not under the applicator’s control, e.g., changing weather conditions. To reduce mis- understanding, we suggest an ongoing dialogue between specialty crop growers and their neighbors who grow corn and soybean and with commercial spray applicators who are likely to use 2,4-D and dicamba. Help these individuals better understand specialty (fruit, vegetable and nursery crops) production and the impact of it on the state’s economy. Promote awareness among agronomic crop producers that vineyards, extensive landscape plantings, or other susceptible crops are located in their neighborhood. Given the recent rapid growth in the number of vineyards, it is likely that some neighboring farms don’t even know grape growers exist in their vicinity, let alone the cost involved in establishing just one acre of wine grapes or the potential value of the crop. Creating and maintaining a heightened awareness of the industry is probably the most important way to reduce risk of future herbicide damage and the lawsuits that will inevitably follow. The following steps may be useful to help the specialty crop industry develop a process for creating and maintaining awareness and reducing the risk of drift damage.

Step 1. Inform your neighbors. Develop and maintain a good relationship with your neighbors. A good relationship starts with open communication. Offer a tour of your operation, explain how damaging drift of glyphosate, 2,4-D and dicamba can be to your crops. In the case of vineyards, make sure to point out the potential for herbicide drift to cause yield loss, poor grape quality, increased susceptibility to cold injury, and reduction in long-term profitability. Discuss the possibility of planting buffer vegetation between your crops and your neighbors’ crop(s) to reduce risk.

Step 2. Mark your farm or vineyard on an online database. Neighboring farmers and commercial spray applicators will need accurate information on where specialty crops are being grown. The Ohio Department of Agriculture has launched a website designed to incorporate coordinates for fields planted to sensitive crops into Google Maps. This site is known as the Ohio Sensitive Crop Registry (Figure 6) (agri.ohio.gov/scr). Applicators can check this website for proximity of sensitive crops to fields they are planning to spray. If you farm near roadways or other rights-of-way contact your county or state highway department, power company, etc., since hormone-type herbicides are likely used for weed control in those situations already.

Figure 6. Screenshot of the home page of the Ohio Sensitive Crop Registry website. Pesticide Safety Education Program, Ohio State University Extension 77 Reducing 2,4-D and Dicamba Drift Risk to Fruits, Vegetables and Landscape Plants—page 5

Step 3. Manage drift of the herbicides used on your own farm or vineyard. Set an example of pesticide stewardship. Fruits and vegetables include the most intensively sprayed crops grown in the United States. Consider the unspoken message you send to the community every time you apply pesticides, especially when using high pressure/high volume equipment. While many herbicides are registered for fruits and vegetables, most have severe restrictions due to the inherent high sensitivity of most crops. In some cases the herbicide injury problem is caused by an application made by the owner, rather than by a neighbor. The likelihood of drift is a multiple of many factors, but some important ones are wind speed, droplet size (determined primarily by nozzle type), the height of the nozzle above the ground or canopy, and the operating pressure. Drift can be minimized by spraying on a morning or evening with low but not zero wind conditions (3–10 mph), keeping the spray boom and nozzles close to the ground, reducing pressure (less than 30 psi), and using low drift nozzles that generate large droplets.

What if drift damage occurs or is suspected? Know the symptoms of 2,4-D and dicamba injury on your crops and plan on scouting regularly during the time when grain growers are spraying (Figures 1 and 2). Early symptom detection (within a few days of drift) is important if you hope to detect residues of the causal agent—a data point that may be of great value in obtaining compensation. Prevention is better than cure. We encourage open and frank communication between all parties. Spell out the risk. Inform your neighbors about the high dollar value per acre of the crops you grow. Many specialty crops, and especially grapes, are relatively small in acreage but high in value, and are highly sensitive to trace amounts of 2,4-D and dicamba. Many are perennials and the consequences of drift damage can be dire and long-lasting.

Filing a drift complaint Even with the best of intentions drift incidents can happen. Before filing a drift complaint, talk to other people such as an Extension Educator to gather additional information. It is also a good idea to inform the suspected pesticide applicator about your concerns and try to work out a satisfactory solution. Being proactive when problems are first observed is critical. Document when symptoms were first noted and any knowledge you may have of pesticide spraying on adjacent properties. Take lots of pictures of damaged and injury-free plants, including close-ups. While laboratory analysis is not always called for, taking samples of damaged tissues is a good idea. Take samples from several plants, seal them in a zip-close plastic bag, and place them immediately in a freezer. It is also a good idea to take a second sample of tissues from plants of the same cultivar that are not showing injury symptoms. If you are convinced that your crops or landscape plants were damaged by herbicide drift, you can file a complaint with the office of Pesticide and Fertilizer Regulation at the Ohio Department of Agriculture. Call 1-800-282-1955, then select option 31 and tell the operator that you want to file a pesticide use complaint. It is also very helpful if you can provide the name and address of the pesticide applicator. This could initiate an investigation.

For more information contact: Dr. Doug Doohan Professor of Horticulture and Crop Science OARDC 1680 Madison Avenue Wooster, OH 44691 Email: [email protected]

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78 Pesticide Safety Education Program, Ohio State University Extension Managing Downy Mildew in Organic and Conventional Vine Crops Sally Miller Department of Plant Pathology, Ohio State University Extension FACT SHEET Agriculture and Natural Resources

HYG-3127-09 Managing Downy Mildew in Organic and Conventional Vine Crops

Ron Becker Sally A. Miller OSU Extension, Wayne County Department of Plant Pathology

owny mildew can be a serious disease on any the leaf. These lesions then turn brown and may drop Dvine crop, but may be especially devastating to out of the leaf. The “checkerboard” arrangement of cucumbers where the appearance of initial symptoms lesions is characteristic of cucumber downy mildew. and complete defoliation may be separated by only Symptoms normally appear 4–12 days after infection. a few days. On cantaloupe, the somewhat angular lesions tend to have a yellow halo around them. On watermelon, the Symptoms spots may or may not be angular, normally turning Downy mildew causes a variety of symptoms de- brown or black with the leaf developing an upward pending on cucurbit type. On cucumber, water-soaked curl. On pumpkins and winter squash, the symptoms lesions on the underside of the leaf are often observed may resemble powdery mildew, causing a yellow spot- first. Yellow, irregularly shaped lesions confined by ting that tends to brown out. As the lesions age, they the small leaf veins appear soon after on the top of usually become necrotic on all types of cucurbits and

Figure 1. Initial downy mildew symptoms on cucumber Figure 2. Advanced downy mildew symptoms on cucumber Pesticide Safety Education Program, Ohio State University Extension 79 Copyright © 2009, The Ohio State University Managing Downy Mildew in Organic and Conventional Vine Crops—page 2

Figure 3. Downy mildew symptoms on cantaloupe Figure 4. Downy mildew symptoms on watermelon

the leaves often senesce. This dieback is normally first Causal Organism noticed on the oldest leaves near the center of the plant. Downy mildew is caused by Pseudoperonospora Regardless of the variability in appearance of cubensis, an oomycete pathogen more closely re- the leaf lesions among the different cucurbits, the lated to water molds such as Phytophthora than one similarity and diagnostic sign is the presence to true fungi. There are multiple pathotypes of of purplish-gray sporangia on the bottom side of P. cubensis; watermelons, pumpkins, and squash the leaf within the lesions. These are most readily are incompatible with several pathotypes, while observed when conditions are cool and moist, with cucumbers and cantaloupe are susceptible to them or without the aid of a hand lens. They may also all. There are also several strains within each patho- appear when an infected leaf is placed in a closed type, to which various cultivars of each type of plastic bag with a damp paper towel for 12–24 hours. cucurbit show varying degrees of susceptibility. The leaves are the only portion of the plant directly P. cubensis can survive and sporulate only on green affected by downy mildew, though the resulting loss (living) tissue of the host, and therefore cannot natu- in leaf surface can cause loss of yield, misshapen rally overwinter north of Mexico or the southernmost fruit, and sunscald. extremes of the United States.

Figure 5. Downy mildew symptoms on pumpkin Figure 6. Close-up of downy mildew on pumpkin

North America or use of transplants produced in the southern United States or northern greenhouses. New strains of downy mildew have also developed that are resistant to commonly used fungicides, and have overcome the genetic resistance of some cultivars. These midseason infections have resulted in heavy yield losses where preventive measures have not been taken.

Management Cultural Practices The same cultural control measures are suggested as part of an IPM effort whether a crop is conventional Figure 7. Purplish-gray sporangia on the bottom or organic, in that they may help to reduce or delay side of a cucumber leaf the chances of an initial infection. Sporangia are the reproductive structures and 1. Despite some strains of downy mildew overcom- also spread the disease on wind currents. Sporangia ing currently available genetic resistance, the use are produced on the undersides of the leaves when of disease-resistant or tolerant cultivars is still conditions are humid and nighttime temperatures highly recommended as some degree of resistance are between 55 and 75 degrees F. The transport and remains. A list of these can be found at the North survival of these sporangia are highly dependent on Carolina State University Cucurbit Breeding web weather conditions. Cloudiness is especially impor- site at http://cuke.hort.ncsu.edu/cucurbit/cuke/ tant as direct sunlight or excessive UV light can cause cukemain.html. the sporangia to desiccate. Rainfall can also wash the 2. Select growing sites with good air drainage, full sporangia out of the air if it occurs before the spo- sunlight, and low humidity. rangia travel much of a distance from source area, 3. Avoid overhead irrigation to prevent leaf wet- or it may help to deposit them in production fields. ness. Upon deposition of the sporangia on a leaf surface, 4. Insure adequate, but not excessive fertility. the absence of free moisture on the leaf may prevent 5. Monitor the crop frequently, and make use of the infection, though only 2–6 hours of free moisture North American Plant Disease Forecast Center are required. Likewise, temperatures outside of the at http://www.ces.ncsu.edu/depts/pp/cucurbit to acceptable range for infection (41–82 degrees F) may monitor reports of downy mildew throughout the also inhibit infection. country. Local updates are also available on VegNet For many years, downy mildew was not reported (http://www.ag.ohio-state.edu/~vegnet/). in Ohio cucurbit fields until late August or Septem- 6. If early in a downy mildew epidemic, removal of ber, being dependent on remnants of hurricanes to infected plants may help to slow the spread of the carry the spores northward. Presence of the disease disease. When doing this, make sure not to spread was often considered inconsequential as many crops the disease by hand or infested equipment. were considered mature, and the loss of leaf surface at that point did little to reduce the yield of crops such Chemical Control as pumpkins. For late cucumber or melon plantings, For conventional growers, it is suggested that pro- fungicides could be applied for control measures. tectant fungicides be applied on a 7–10 day schedule More recently, cucurbit downy mildew has been upon emergence of the seedling or transplanting. reported as early as late June, possibly due to over- When downy mildew is detected in the area, a curative- wintering of the disease in greenhouses in northern type fungicide should be added to the spray mixture

and the spray schedule should be shortened to 5–7 Resources days. Consult the Ohio Vegetable Production Guide “Downy Mildew in Cucurbits,” National Sustainable (OSU Extension Bulletin 672) for recommendations Agriculture Information Service, http://attra.ncat. and make sure to rotate fungicides with different org/attra-pub/downymildew.html#ref4 modes of action. North Carolina State University Cucurbit Breeding For organic growers, there are several alternative Program, http://cuke.hort.ncsu.edu/cucurbit/ fungicides labeled for cucurbit downy mildew, in- cuke/cukemain.html cluding copper-based fungicides. Growers should be “Cucurbit Downy Mildew Forecast Home,” North cautious in applying copper, as it can be phytotoxic American Plant Disease Forecast Center, http:// to cucurbits, and high levels in soil are toxic to earth- www.ces.ncsu.edu/depts/pp/cucurbit worms and other beneficial organisms. Phytotoxicity “Update on Managing Downy Mildew in Cucur- is most common during cool, moist conditions, which bits,” Vegetable MD Online, Cornell University, are also the most favorable for downy mildew. A list http://vegetablemdonline.ppath.cornell.edu/ of the other alternative fungicides can be found at NewsArticles/Cuc_Downy.htm the National Sustainable Agriculture Information “Cucurbit Downy Mildew Caused by Pseu- Services “Downy Mildew in Cucurbits” web page doperonospora cubensis,” Extension Collab- at http://attra.ncat.org/attra-pub/downymildew. orative Wiki, http://collaborate.extension.org/ html#ref4. Make sure to check with OMRI http:// wiki/Cucurbit_Downy_Mildew_Caused_by_ www.omri.org and your organic certifier to determine Pseudoperonospora_cubensis if the suggested products are currently considered Acknowledgments acceptable for organic production. All photos by Sally A. Miller.

Visit Ohio State University Extension’s web site “Ohioline” at: http://ohioline.osu.edu Ohio State University Extension embraces human diversity and is committed to ensuring that all research and related educational programs are available to clientele on a nondiscriminatory basis without regard to race, color, religion, sex, age, national origin, sexual orientation, gender identity or expression, disability, or veteran status. This statement is in accordance with United States Civil Rights Laws and the USDA. Keith L. Smith, Ph.D., Associate Vice President for Agricultural Administration and Director, Ohio State University Extension TDD No. 800-589-8292 (Ohio only) or 614-292-1868

82 Pesticide Safety Education Program, Ohio State University Extension