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Home , Cover crop, Juglone

Van Sambeek, Jerry. 2017. Cover to improve health and pollinator habitat in nut . Missouri Nut Growers Association (MGNA) Newsletter. 17(2): 6-12. Cover Crops to Improve Soil shade than under full sun while shade- intolerant cover crops like field peas and Health and Pollinator Habitat oats do poorly under moderate shade. in Nut Orchards: Part II Normally, in an is discouraged to minimized damage to tree Jerry Van Sambeek, Research Plant roots. Deep tillage to incorporate a cover Physiologist, USDA Forest Service as is also discouraged Northern Research Station, Columbia, MO as it speeds up the microbial loss of [email protected]; 573-875-5341 nitrogen and and slowing ext. 233. (…continuing Jerry’s article from the the gains in soil health expected from a Winter 2017 issue and a hard copy for those who cover crop. The trees and cover crops will didn’t take notes at the annual meeting!). both benefit from no-till practices and other management practices. Integrating cover crops into a nut We have more options when using orchard can have some unique benefits cover crops in our orchards than farmers and problems not found when used cover because we can establish and maintain crops during the fallow period between perennial forbs as cover crops. One cash crops. Studies show ground covers suggested cover crop for orchards is a mix can reduce hardwood tree growth of moderately shade-tolerant white clover anywhere from a few percent to more than for and weed suppression 70 percent in the case of tall fescue (Fig. and perennial ryegrass for nutrient 1). This means if it takes 3 years to put on scavenging, and soil building. Bud burst one inch of diameter growth in a weed-free and flowering on growing in a planting, it will take more than 9 years if perennial grass sod can be delayed 4 to 5 growing in a tall fescue sod. Impacts on days due to cooler soil temperatures nut production appear to be even greater. lessening the risk from late spring frosts. Perennial cool-season cover crops should be left to flower, produce seed (unless the cover crop itself can become a weed), and then go dormant over the summer to help conserve soil moisture. Summer mowing is discouraged because it will stimulate new plant growth that will again actively compete with the trees for available soil moisture and nutrients. An added value of using forage cover crops in an orchard maybe the production Fig. 1-Tall fescue as a ground cover or cover crop of high quality forage for . When in a slow growing walnut stand leaves little soil grown under moderate to dense shade nitrogen for the trees. most plants produce less, but higher The amount of sunlight available to the quality forage (higher crude protein and ground cover in an orchard will depend on less non-digestible fiber). Care is needed the row orientation, size, and crown density when selecting cover crop species to of the trees. In a mature nut orchard less minimize risks from bloat, nitrite poisoning, than 50% of incoming solar radiation and toxic compounds that occur naturally reaches the ground cover. Some shade- or form if hay is not properly harvested. tolerant cover crops like Kentucky According to Kansas State, the plant to bluegrass, sweet clover, white and red worry most about is hairy vetch, one of the clover have better growth under moderate most frequently used cover crop species. 6 If the orchard, you should follow seem to increase the incidence of browsing the UMCA’s silvipastural guidelines to and buck rub. Cover crops are also likely minimize compaction and overgrazing. to increase the number of mice and voles Guidelines recommend creating multiple followed by snakes. Pecan growers may small paddocks so livestock can be rotated not want to mow or the cover crop when forage cover is reduced by two-thirds after August 1 or until shuck split to lessen or plants grazed early in the rotation show movement of nut-damaging stink bugs into new growth. To minimize compaction in the trees. the orchard, maintain some open pasture paddocks, so livestock can be removed from the orchard when soil moisture is near field capacity. When choosing which cover crop to use, consider how plant residues in the fall will impact the harvesting operation. Plants with tall woody stems will make it difficult to pick up the nuts unless mowed before harvest. Warm-season perennials are weakened if fall mowing is not delayed until after a killing frost. Most mechanical harvesters are not designed to handle Fig. 2-Hairy vetch, an excellent cover crop large volumes of grass or forage. and N-fixer, in full flower.

Although Daikon can be used to In Managing Cover Crops Profitably, break up the plow pan found under many Andy Clark (2007) says there is a cover orchards, it is easily pulled up and jams crop to fit just about every situation and mechanical nut harvesters in addition to suggests starting by considering the top leaving holes in the orchard floor into which recommended cover crops species for your nuts disappear. region. For Missouri, he recommends When cover crops are planted in black crimson clover, red clover, sweet clover, walnut and to a lesser extent in pecan and hairy vetch, cereal , annual ryegrass, hickory plantings, some consideration spring oats, and because of should be given to the susceptibility of the their properties as nitrogen sources, soil cover crop to juglone. Numerous lists exist nutrient scavengers, soil builders, on the web as to what plants are fighters, subsoil looseners, and weed supposedly tolerant and susceptible to fighters. juglone although few cover crop species Andy Clark did include an example for a are on these lists. It is important to note sloping orchard needing a cover crop to that improving soil health, i.e. increasing control erosion, contribute organic matter the organic matter and the populations of and N, attract beneficial organisms, limit soil microbes lessens the likelihood of rodents and other pests, conserve soil juglone occurring even if a species moisture, and not tie up nutrients during is listed as susceptible. key periods of fruit or nut development. He Although legume cover crops can recommended selecting a cover crop that provide much of the needed nitrogen, they does not produce too much N causing do have a down side. , especially excessive leaf growth on the trees, can be the clovers, aggressively take up potash a perennial or reseeding annual, is low and orchards may require application of K growing and needs minimal management, . Clover and hairy vetch ground uses water efficiently, releases nutrients covers (Fig. 2) are attractive to deer and during the growing season, and harbors or 7 attracts few pests. He recommended white they nest in the soil and excavate clover or possibly strawberry clover underground tunnels. (although they attract pocket gophers) mixed with quick-growing reseeding soft brome or annual ryegrass (although they may require some control by periodically mowing). He suggested using reseeding winter annuals such as crimson clover, rose clover, subclover (south Missouri only), annual vetches, or an annual medic as alternatives. Two tables were distribution at the 2017 MNGA annual meeting that rank grasses, legumes, or other broad-leaved species Fig. 3-Bees actively forage for pollen and either for their value as a cover crop in nut nectar that results in movement of pollen. orchards or for their establishment, growth characteristics, management, and Other beneficial insects that benefit from utilization. Table 1 is an example of these pollen and nectar sources during part of tables that shows values for 6 of the >50 their life cycle include predatory beetles, traits compiled for 20 of the >60 species. lacewings, and parasitic wasps. These The full tables most likely will also be insects prey on destructive insects available in a future issue of The Nutshell including aphids, slugs, caterpillars, and published by the Northern Nut Growers grasshoppers. Association or can be obtained by Trees and shrubs can provide significant contacting Jerry Van Sambeek. forage (pollen and/or nectar) and many serve as larval hosts for butterflies and COVER CROPS AND POLLINATORS moths. Nearly all native trees, shrubs, and Declining populations of the monarch woody vines including walnut, pecan, oak, butterfly and honeybees have brought and chestnut are utilized by pollinators. national attention to the importance of Dumroese and Luna (2016) suggest our pollinators and other beneficial insects. nut trees can support more than 120 Over 100 agricultural crop species in North different species of butterflies or moths. America and more than 75% of the food Honey bees prefer to forage on the lee we eat depends on a pollinator to achieve side of trees and stop pollinating when it full potential yield. Under the ‘National gets too windy. Some studies show Strategy to Promote the Health of Honey increased pollination efficiencies extending Bees and Other Pollinators,’ almost 10 to 15 times the height of the trees. 200,000 acres have already been signed Legume cover crops are excellent up for planting to a mix of forbs to provide sources of pollen and nectar for pollinators nectar, pollen, and nesting sites. and beneficial insects in addition to their Although honey bees facilitate being able to boost . UMCA pollination of more than 120 crops, there researchers found that the number and are nearly 4,000 different species of bees diversity of beneficial predatory and found in the United States. Most species parasitic insects were higher in a walnut are solitary bees, meaning each female alley-cropping practice than in a pure locates and provisions her own nest with stands. McGraw and Smith also pollen before laying eggs (Fig. 4). Most reported that planting legumes in pecan bees require undisturbed areas because orchards was followed by a build-up of beneficial insects. Recognize that when 8 the cover crop goes dormant or dies, it is chemicals move through a plant making also likely to drive insect pests into the tree most parts toxic to pests as well as canopies such as stink bugs that feed on pollinators and beneficial insects. They can the immature nuts. also persist in the soil and absorbed later Although grass cover crops do not by the next crop. provide nectar, they can provide pollen. Grass pollen usually has a lower protein content than the pollen of broad-leaved plants making grass pollen marginally attractive to bees. Cover crops of high value to honey, native, and bumble bees, butterflies and moths, and other beneficial insects include annuals such as buckwheat, canola, crimson clover, phacelia, sunn hemp, and hairy vetch; biennials such as partridge pea, sweet clover, forage radish, and turnips; and perennials such as alfalfa, Fig. 4-Five-year-old native wildflower kura clover, white clover, red clover, border seeded without native grasses. sainfoin, and the perennial vetches. Many An easy option for restoration for of these same plants also provide positive pollinator habitat in your orchard is to benefits for improving soil health. establish permanent narrow strips of native Buckwheat is one of the best cover wildflowers within the tree rows or along crops for attracting bees and beneficial fence rows and wider strips along orchard insects. It grows rapidly smothering other boundaries (Fig. 4). If you want strips to and is easily killed by mowing also include grasses, use bunch grasses before the seed matures (it can be invasive like orchard grass, timothy, or our native otherwise). Flowering vines and plants little bluestem or prairie dropseed. These with weak stems are usually better cover strips can provide undisturbed areas for crops than plants with erect stems because solitary bees to dig underground tunnels they can smother and suppress growth of for nesting. Mixes with eight or more native other plants with less above ground wildflowers usually provide a sequential biomass. Last summer, Steve Kirk source of pollen and nectar. observed six different species of Consider including milkweeds in native bumblebees working our hairy vetch plots wildflower strips as milkweeds are the sole on the same day. It is important when managing for pollinators to use a mix of species to assure flowers are present throughout most of the growing season. In a nut- producing orchard, cover crops should be chosen that are not blooming when insecticides need to be applied to control insects such as the pecan weevil. If that’s not possible, plan to mow the cover crop just before spraying insecticides or spray late in the day when bees are least active. Avoid the use of systemic insecticides, Fig. 5-Blackberries growing and producing especially the neonicotinoids, as these fruit under a row of hickory trees. 9 source of food for the monarch butterfly. can do custom mixes designed to address Missouri has 18 species of milkweed, half your specific soil or grazing needs. If of which have seed commercially available. mixes include legumes, use the correct They are adapted to a wide range of soil rhizobial inoculum at the same time to conditions, so one or more species should maximize nitrogen benefits. Several be adapted to our orchard . companies have developed their own A third option for improving pollinator inoculum with a broad mix of rhizobial habitat is planting flowering shrubs and strains that are likely to nodulate both small trees within the tree rows. If pruned seeded forage legumes and native to remove lower lateral branches, we legumes. Look for inoculums that also should be able to harvest nuts from under contain beneficial mycorrhizal fungi to these trees and shrubs. If soils are not well boost growth of most cover crops. drained and are low in organic matter, Valuable sources of information I found on shrubs will need to be selected that the web include Center Seeds (Minster, tolerate the accumulation of juglone in OH; http://www.centerseeds.com) which is black walnut orchards. If you use other nut a network of dealers with seven locations or fruit trees, they can also be a source of in Missouri, Green Cover Seed (Bladen, additional revenue from the orchard. NE; http://greencoverseed.com), and Pollinator-friendly species tolerant of Walnut Creek Seeds (Carroll, OH; juglone and their bloom time include http://walnutcreekseed.com). witchhazel (Jan-Mar), redbud (Mar-Apr), plums (Mar-May), service berry (Mar-May), PRIMARY REFERENCES USED pecan (Apr-May), black raspberries (Apr- Belcher, E. 2014. The cover crop specialists Jun), peaches, cherries, pawpaw (Apr- guide. Center Seeds. Clark, A., ed. 2007. Managing Cover Crops May), sassafras, elderberry (Jun-Jul), and rd willow (Apr-May), but not apples, Profitably. 3 edition. Sustainable Network, Beltsville, MD. 246 p. blueberries, grapes, or blackberries (Apr- Dumroese, R.K., and Luna, T. 2016. June). Growing and marketing woody species to Under the Conservation Reserve support pollinators. Tree Planters’ Notes Program, the USDA Service Agency 59(2): 49-60. plans to enroll nearly 270,000 acres of Finney, D. M. and Kay, J.P. 2016. private lands in a special pollinator-specific Functional diversity in cover crop initiative. In addition, the USDA NRCS increases multifunctionality of an agricultural plans to fund up to $4 million in cost-share system. Journal of Applied . DOI: programs to establish and improve habitat 10.1111/1365-2664.12765. under the Monarch Butterfly Habitat Johnson, H. and Liebig, M. 2015. Cover Development Project. Crop Chart. USDA-ARS Northern Great Plains Research Laboratory. SOURCES FOR COVER CROP SEED http://www.mandan.ars.usda.gov. Agronomic crops that can be used as MCCC. 2014. Midwest cover crops field cover crops like wheat, rye, oats, guide. ID-433. MCC Council. 161 p. SARA. 2015. Cover Cropping for Pollinators , and clovers can usually be and Beneficial Insects. purchased from a local farm supplier. New Research and Education. 16 p. seed companies have started that Van Sambeek, J.W. and Garrett, H.E. 2004. specialize in seed bred for use as soil- Ground cover management in walnut and other improving cover crops like the Daikon hardwood plantings. Pp 85-100 in USDA FS radish and sunn hemp or as cover crops Gen Tech Rep NC-243. that can also be grazed like grazing corn. These companies have prepared mixes or

10 Table 1. Compatibility, shade tolerance, 90% of cropland) has led to selection for and nitrogen source for some common -resistant weeds and the need cover crop species. to develop of crops resistant to multiple

. If applications are

not done correctly, volatilization and drift

from these plantings pose significant risk to adjacent nut orchards and other crops. The new concern is use of , a

e to bees e benzoic acid that is readily absorbed by

both foliage and roots of broad-leaved

Shade tolerance Shade source Nitrogen builder Soil Valu value Grazing Cover crop Compatibility plants with a half-life of about 14 days in Alfalfa D D A A A A the soil. It quickly translocates throughout Annual ryegrass C C F A F B a plant where it acts as an -like Bluegrass B B F B D A growth regulator. It has been used to Buckwheat -- D D C A F control broadleaf weeds in corn, sorghum, Cereal rye B B F A F C pastures, and turf as well as woody plants Cowpeas -- C A D A C in non-crop areas. Unlike glyphosate, Crimson clover B B B B A A dicamba is easily volatilized from leaf Crownvetch A A A -- B D surfaces on hot days. We understand Field (winter) peas -- D B C C B more than 100 complaints have been filed Hairy vetch B B A B B F against Monsanto Company because of Oats B D F C F A volatility and drift issues of dicamba to non- Orchard grass C B F B F B target plants. Monsanto Company has denied any Radish -- D D A A C liability because of off-label use of dicamba Red clover B B B C B A by growers and applicators. One case Redtop B C F B F B involves more than 270 pecan trees that Soybeans A -- C D C -- were injured or killed following spraying of Sweet clover B B A A A C an adjacent cotton field. Missouri’s largest Tall fescue F C F B F B peach grower, Bader , Inc. in the White clover C B A C A A Missouri Bootheel, claims more than 7,000 Winter wheat A C F C F B peach trees showed damage in 2015. The A=excellent, B=very good, C=good, D=fair, number grew to 30,000 trees in 2016. The F=poor, and an – means data not available. University of Missouri is developing plans to determine susceptibility and characterize symptomology on a wide range of New Threat to Our Nut landscape plants including apple, walnut, Orchards pecan, and oak. As Bill Reid suggested a few years ago, know what your neighbors (Jerry Van Sambeek and Michele Warmund collaborated on are planting and, if their plans include this article) Roundup and dicamba-ready soybeans In 2017, we can expect to see and cotton, let them know our nut orchards increasing planting of soybeans (Roundup are highly susceptible to dicamba drift and Ready 2 Xtends) and cotton (Bollgard II that they need to be using the newer, XtendFlex) resistant to glyphosate more-expensive non-volatile formulations (Roundup) and dicamba (Banvel, Diablo, and nozzle technology (XtendiMax or Vanquish) in Missouri. Heavy reliance VaporGrip). These formulations minimize on glyphosate-resistant soybeans, corn, the formation of small droplets readily and cotton (some estimates as high as carried by the wind. They were not 11 available in 2016 but should be available in 2017.

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