Eggplant Solanum melongena L., is often colonized by two early season insect defoliators. The Colorado potato beetle (CPB), Leptinotarsa decemlineata (Say), and flea beetles Epitrix spp., emerge from their overwintering sites in early spring and seek out emerging host plants such as eggplant. During the 2009 and 2010 growing season, field studies were conducted to investigate the impact of inter‐planting eggplant into a crimson clover (CC), Trifolium incarnatum L., winter cover crop on populations of flea beetles, CPB and their associated arthropod predators. The experiment consisted also of two levels of insecticide usage such as an application of azadirachtins plus pyrethrins followed by several applications of spinosad or no insecticide sprays as subplot treatments. During both study years, significantly fewer (adults, larvae and egg masses) were found on eggplant inter‐planted into CC than in bare‐ground (BG) eggplant plots. Although flea beetle abundance was greater in BG eggplant during 2010, they appeared to be less influenced by the presence of CC than were CPB. Additionally, there was no apparent impact of insecticide treatment on CPB populations on eggplant inter‐planted into CC. However, there was a decline in CPB following treatments with insecticides in BG eggplant plots. This suggests that a winter cover crop such as CC can be used to help manage CPB in eggplant, however, using this tactic in tandem with insecticide sprays may not result in greater CPB management.

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The effect of using crimson clover (CC) (Trifolium incarnatum L.) as a companion plant on crop growth, marketable yield and insect feeding injury was examined using Eggplant, Solanum melongena L. as the neighbouring cash crop. There were two subplot treatments, which included applications of organic insecticides and no insecticides. Planting eggplant directly into CC did not improve most eggplant growth variables and resulted in a yield reduction during year 1. During year 2, when the CC was strip-tilled prior to transplanting the eggplant, several eggplant growth variables were more strongly enhanced in CC than bare-ground (BG) habitats. Eggplant in CC plots suffered less damage by insect folivores but yields were similar among treatments. There were no benefits of using organic insecticides with respect to increased marketable yields in CC treatment plots, but there was an increase in marketable yield in sprayed compared with unsprayed BG subplots. If properly managed, CC may help protect eggplant from insect feeding injury; however, this may not cause an increase in marketable yield.

Producers in the Mid-Atlantic region of the United States often use prophylactic pesticide sprays in their fields to increase wheat (Triticum aestivum L.) yields regardless of disease or insect pest levels. This study was carried out at two sites during each of two field seasons to evaluate th-e effects of pesticide applications (fungicides and insecticide) on insect abundance, beneficial arthropods, foliar damage and grain yield in winter wheat. Insecticide applications reduced densities of cereal leaf beetle (CLB) and CLB damage of flag leaves at the Queenstown and aphid at the Upper Marlboro study site compared to controls during 2009 and 2011 field seasons, respectively. However, insecticide application also reduced arthropod predators at Queenstown in 2009. Fungicide applications reduced leaf spot severity symptoms at Queenstown in 2009 and both sites in 2011. Grain yield was negatively correlated with the percentage of severely damaged flag leaves during the 2009 growing season when diseases and insects pressure was greatest. Nevertheless, yield increase associated with application of pesticides (fungicides) was observed only at one out of four siteÀyear combinations. Results from this study suggest that prophylactic sprays will not enhance wheat yields in the absence of high pest pressure.