Habitat Enhancement for Beneficial Insects in Vegetable and Fruit Farming Systems

Habitat Enhancement for Beneficial Insects in Vegetable and Fruit Farming Systems

Summary

Objectives
1.) Screen selected plant species, including cover crops, for attractiveness and habitat value to predators and parasitoids of key pests of cabbage and squash;
2.) Develop production systems for cabbage and squash using habitats altered to favor natural enemies of their insect pests;
3.) Evaluate these agroecosystems, including economic comparisons with monocropped systems.

Approach
Ten vegetable growers in Arkansas and Oklahoma, and three university professors whose responsibilities included both research and extension were involved in project design, on-farm and research center trials, evaluation and information sharing. Two of the Arkansas farms belonged to and provided educational demonstrations for nonprofit organizations. The other eight farms ranged in size form 12 acres to 220 acres, with 1/2 to 4 acres in vegetable production. All farmers grow a variety of vegetables, fruits, and flowers for local markets.

Plants were chosen for screening based on reports from similar trials and the experiences of participants. Native and non-native flowers planted in screening plots included Monarda citriodora, Ami magus, Cosmos bipinattus, Achillea millefolium, Asclepiad tuberoses, Lustrous pychnostachya, Gaillardia sap., Rudbeckia hairdo, Solidago sap., and Coreopsis sap. Herbs included bronze fennel, basil, cilantro, dill, and borage. Winter cover crops included crimson clover, hairy vetch, subterranean clover, white clover, alfalfa and rye. Records were kept on cultural activities, blooming period and insect activity. Researchers vacuumed insects off the plants and stored them for lab identification.

Results
Plants noted by many farms as being highly attractive to beneficial insects included basil, cilantro, dill (and all flowering plants in the umbel family), arrow, buckwheat and crimson clover. Other flowers noted by one to two farmers as highly attractive were anise hyssop, garlic chives, mints, goldenrod, asters and other native plants in the composite family, and a commercial mix that contained radishes.

Participants evaluated several strategies for incorporating habitat enhancing plants into cropping systems: companion planting, strip planting, and border or island planting. To evaluate the systems, cabbage was grown with and without habitat enhancing plants. The ratings were as follows:

Companion planting - a mix of different species of plants within a row or bed - was rated as difficult to manage due to varying cultural needs of species i.e. planting time, harvest time and methods of planting and harvesting.

Strip planting - alternate rows or beds of habitat plants and vegetables - were rated as most easily adapted to vegetable production systems. Farmers and researchers also managed cover crops as strips, tilling or mowing to kill winter cover crops before planting cabbage in the strips.

Border planting - fence rows, field edges, or islands of "habitat" plants - were also rated as reasonably adaptable.

In all systems, cooperators agreed that diversity is desirable. Plant species that bloom at different times of the year provide a more consistent supply of pollen or nectar. Cooperators also agreed that habitat plants should have additional value to the farmer as cut flowers, herbs, green manures or forages.

Farmers cited interaction with other farmers, learning new things, and contributing to knowledge about sustainable agriculture as important benefits from this project. Workshops with project researchers covering insect collection and identification facilitated information exchange between farmers and researchers. From planning sessions through year-end evaluation, all participants worked together as equals. On-farm field days hosted by the participants reached out to the larger community. All farmers stated that they have changed their farming practices and/or the way they view insect and crop interactions, as a result of this project. They continue to share what they learned with other farmers and with people who buy their produce.

Research results from Alabama indicated significantly lower numbers of diamondback moth larvae when cabbage was planted in strips between a fall-established planting of legumes as compared to cabbage planted in clean-tilled plots. White clover was superior to alfalfa, subterranean clover, crimson clover, and common vetch in terms of lowest cabbage damage rating.

December 1996.