MCMINVILLE, Tennessee – Winter cover crops, specifically a ryegrass/crimson clover mix, appear to protect susceptible deciduous trees from the flatheaded appletree borer, while also effectively managing weeds, according to results of a Tennessee State University study. The results could be useful for orchards, nurseries, urban landscapes and agroforestry producers in managing the significant economic pest.
In a Southern Sustainable Agriculture Research & Education (SSARE) On-Farm Research Grant, researcher Karla Addesso and her colleagues found that the winter cover crops camouflage the tree trunks from the pest, making it less likely to lay eggs. Larvae can girdle the trunks as they begin tunneling into the trees. The $14,997 grant-funded project looked at red maple trees, but Addesso said that the practice is useful for any tree susceptible to the pest.
“We chose to use red maple because it is a preferred host of flatheaded appletree borer and can cause substantial damage. Red maples are a high value commodity in the woody ornamental nursery,” said Addesso. “But the borer will also attack apples, dogwoods and many other smooth barked deciduous trees. This research could be applicable to any tree producers/orchards where the flatheaded appletree borer is located.”
In the study (OS14-084), “Incorporating a Cover Crop into Field Grown Nursery Production to Manage Flatheaded Appletree Borer with the Simultaneous Benefit of Improved and Sustainable Weed Management,” the presence of cover crops reduced pest attacks by 95 percent. In addition to acting as a barrier, the cover crops also reduced the temperatures of the tree trunks, making the trees a less preferable egg-laying site.
“We do not know exactly when the beetles lay their eggs, but they are active from mid-May to the end of June or later. In the first year, we planted wheat and crimson clover based on our knowledge that wheat would be at the proper height by May 1st to block the base of the trees. The crimson clover was added as a nitrogen source,” said Addesso. “In the second year, we planted annual ryegrass and crimson clover, again with the knowledge that the ryegrass would reach an appropriate height by May 1st. This crop combination senesced faster than the wheat and appears to have been more effective at suppressing summer weeds.”
The current treatment practice for flatheaded appletree borer management in newly transplanted trees includes a soil drench of imidacloprid to protect trees from borer damage. However, there are concerns of the effects of the chemical on pollinators.
Addesso said that using cover crops to help manage the pest leads the way for an alternative management practice. Research results found that the presence of cover crops aided to prevent leaching of imidacloprid from the root zone of the trees.
In addition, the cover crops helped suppress weeds, and the presence of cover crops did not cause any unusual secondary pest pressure on the maple trees. Researchers tested for the presence of ambrosia beetle, maple twig borer, maple leaf tier, spider mites, broad mites and potato leafhopper.
Not only do cover crops provide benefits to nurseries and orchards, farmers practicing agroforestry can also take advantage of the alternative system.
“If a farmer is interested in growing a winter grain, he or she can incorporate a wheat or rye and harvest the middles while leaving the rows to protect the newly transplanted trees. The middles are not necessary for protecting the trees, but do act to suppress winter weeds and prevent erosion, which are additional benefits,” said Addesso. “I would probably not recommend releasing livestock to feed on the cover until after July 15 to be sure the trees remain camouflaged through the flatheaded appletree borer active period. After the threat of flatheaded appletree borer has passed, livestock can be grazed in the field as well.”
Research will continue a third year with other cover crops, such as winter rye, and biofumigant crops such as mustards, and to improve management of the cover crop to minimize competition with the tree crop. In addition, Addesso and her colleagues plan to collaborate with researchers in other states to further pursue the ecology and management of the flatheaded appletree borer, as well as its close relatives.
Additional project participants included nursery owner Benji Moore, USDA research horticulturist Donna Fare, and TSU research associate Jason Oliver.
Published by the Southern Region of the Sustainable Agriculture Research and Education (SARE) program. Funded by the USDA National Institute of Food and Agriculture (NIFA), Southern SARE operates under cooperative agreements with the University of Georgia, Fort Valley State University, and the Kerr Center for Sustainable Agriculture to offer competitive grants to advance sustainable agriculture in America's Southern region. This material is based upon work that is supported by the National Institute of Food and Agriculture, U.S. Department of Agriculture, through Southern Sustainable Agriculture Research and Education, under sub-award number: OS14-084. USDA is an equal opportunity employer and service provider. Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture.
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