Plant diversity and its effects on populations of cucumber beetles and their natural enemies in a cucurbit agroecosystem

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Virginia Tech

Populations of striped cucumber beetles (Acalymma vittatum Fabr.), spotted cucumber beetles (Diabrotica undecimpunctata howardi Barber), western cucumber beetles (Acalymma trivittatum Mann.), Pennsylvania leatherwings (Chauliognathus pennsylvanicus DeGeer), Diptera (Order: Diptera), lady beetles (Order: Coleoptera, Family: Coccinellidae), hymenoptera (Order: Hymenoptera), and spiders (Order: Araneae) in a cucumber field and a bordering field of uncultivated vegetation were assessed using yellow sticky traps to determine: 1) the relative abundances of target insects across the uncultivated vegetation and the crop field, 2) relationships between target insects and plant species. In both years populations striped and spotted cucumber beetles and Pennsylvania leatherwings (only in 1995) increased significantly and Diptera decreased significantly in the direction of the crop. The strength of these relationships increased over the season to a peak in August in 1995 and July in 1996 and then decreased in September in both years. There were significant correlations between Diptera and sweet-vernal grass in 1995. In 1996, cucumber beetles were correlated with wild violet (Viola spp.) and white clover (Trifolium repens); Diptera with wild violets; and the lady beetle Coleomegilla maculata with goldenrod (Solidago spp.), English plantain (Plantago lanceolata), and marjoram (Origanum spp.) in 1996. This study demonstrated the potential value of increasing the diversity of a cucumber field to control insect pests (and thus reduce pesticide useage) as well as suggested specific plants that influenced insect populations.

community ecology, cucumbers, Pennsylvania leatherwing, Diptera, lady beetles, wild violet, clover, goldenrod