Pest Management and Orchard Floor Management Strategies to Reduce Pesticide and Nitrogen Inputs

View the project final report

• 1991 annual report

Commodities

• Nuts: pecans

Practices

• Pest Management: general pest management

[Note to online version: The report for this project includes graphical figures that could not be included here. The regional SARE office will mail a hard copy of the entire report at your request. Just contact Southern SARE at (770) 412-4787 or sare@griffin.uga.edu.]

The purpose of this study is to develop and test a pest management and orchard floor management system for use by pecan growers. The system utilizes winter legumes interplanted in the orchard to produce and manage native beneficial insect predators and parasites for early-season aphid control. The system also utilizes release of commercially available predators and parasites for mid- and late-season aphid control and control of lepidopterous pests. Legumes are managed to supply the pecan nitrogen requirement.

Beneficial arthropods were more abundant in orchards with legume ground covers compared to those orchards with grass ground covers. These beneficials were attracted into the orchards because of the large aphid populations feeding on the legumes. The high beneficial populations controlled aphids in the pecan canopies, eliminating the need for pesticide applications to control aphids. Benefits of releasing of green lacewings for mid- and late-season aphid control was unclear. Although green lacewing egg laying and pupae were increased by supplemental releases, parasitism of the green lacewing eggs and pupae was increased, thus populations of green lacewings were similar or lower than in orchards without supplemental releases. However, in both cases aphids did not increase to injurious levels because of high lady beetle populations and other aphid predators. Trichogramma releases to control pecan nut casebearer and hickory shuckworm were not successful. Although populations of these two lepidopterous pests were reduced, their damage was above acceptable levels. Legume ground covers produced abundant nitrogen which satisfied the nitrogen requirement of the pecans. Our results indicated that legumes supplied the equivalent of 130 to 165 pounds of nitrogen/acre to the pecan trees. An additional benefit of annual legume ground covers was a reduction in the number of times the orchard required mowing. Because the legumes formed a dense mulch when they senesced, orchards were only mowed twice compared to five to six times with grass ground covers. We estimate that legume ground could eliminate one to two pesticide applications, reduce mowing costs plus supply the nitrogen requirement; however, costs would be added for seed bed preparation and seed, with a net reduction in input costs of about $20 to $40/acre.

To demonstrate the advantages of utilizing winter cover crops of legumes in commercial pecan orchards to produce beneficial insects for the control of aphids and other pests on pecan trees.

To test and evaluate the use of certain commercially available beneficial insects for control of aphids and lepidopterous pests of pecan trees.

Evaluate selected legumes to reduce commercial nitrogen inputs for pecan production.