Striped and spotted cucumber beetles are important insect pests of cucurbits and vectors of the causal agent of bacterial wilt (Erwinia tracheiphila), the most serious disease threat of muskmelon in Kentucky (Hoffman, 1998; Rowell et al., 2002). Adult cucumber beetles and larvae also can cause damage by feeding on cucurbit roots, shoots, and flowers.
Synthetic insecticides such as imidacloprid, permethrin, and carbaryl can be used to control cucumber beetles in conventional vegetable production but are precluded from use in organic production (Rowell et al., 2002). Production of organically grown vegetables is increasing, and new effective organic management practices for cucumber beetles are needed due to the limitations of current practices, which include the use of rowcovers and the botanical insecticide, rotenone (Jolly, 1998; Lopez, 1998; Smith and Henderson, 1998). Rowcovers are only useful until flowering, when they must be removed to allow insect pollination. Rotenone is highly toxic to cucumber beetles, but residual effects only persist for 1 to 3 d because it is not stable in sunlight (Ware, 1994). Also, rotenone is as toxic to humans as many synthetic insecticides, and many organic growers are reluctant to use it (Rowell et al., 2002; Ware, 1994). Pyrethrin is an organic insecticide that is less toxic to humans than rotenone (Rowell et al., 2002) and may be an effective insecticide for cucumber beetles. It is a contact insecticide that causes insects to leave protected areas, exposing them to the insecticidal spray.
Several other organic methods may reduce populations of cucumber beetles. Caldwell and Clarke (1998, 1999) reported that cucumber beetle densities on squash (Cucurbita pepo) were five times less with aluminum-coated plastic (Al-plastic) mulch than with black plastic mulch. No insecticidal treatment was required with Al-plastic, making it cost-effective. Numbers of cucumber beetles in watermelon have been reduced using Al-plastic in place of black plastic mulch, but the results were not statistically significant (P > 0.05; Andino and Motsenbocker, 2004). Companion plants may be planted near cucurbits to attract insects that prey on cucumber beetles. These beneficial insects include pennsylvania leatherwings (Chauliognathus pennsylvanicus) and tachinid flies such as Celatoriae diabrocitae and Celatoriae setosa (Platt et al., 1999). Companion plants thought to attract beneficial insects include buckwheat, cowpeas, and sweetclover (Bowman et al., 1998; Platt et al., 1999). Other types of companion plants are thought to repel cucumber beetles, including radish, nasturtium, and tansy (Rodale Press, 1978). Cucumber beetle numbers in cucumber (Cucumis sativus) have been reduced using corn (Zea mays) and broccoli (Brassica oleracea var. italica) companion plants (Bach, 1980a, 1980b); however, beetle numbers in squash were increased when plots were edged with tomato (Solanum lycopersicum) plants (Bach, 1988). Thus, beetles may be affected differently in various polyculture plantings.
The objective of this research was to examine the use of companion plants, Al-plastic, and pyrethrin as organic methods for managing cucumber beetles in the production of watermelon and muskmelon.
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