Can cover crops reduce leafhopper abundance in vineyards?

economi(about 15%) ) was rarely ­ mechacally important and the ­ nisms leading to reduction were not clear. For example, l , there numwere few differences f in the ­ berr off leafhopperr predators or parasitoids on i the vines in cover cropped versus no coverr sigplots. However, r, there were ­ differnificant between-treatment ­ ences in vine growth. Plots with seasonwide maintenance off a cover crop and resident grasses had a reduction in vine vigor. assoLowerr vine vigor has been ­ ciated with lower leafhopper densities and, in our studies conducted from 1993 to 1996, , those plots with reduced vine revigor often had the greatest ­ leafhopduction in late-season ­ perr density. Cover crops have been used to at­ po­ tract beneficiall insects that will tentially suppress pest populations. Indeed, many grape growers are managing floor vegetation ti as one component off their integrated pest management (IPM) program (Mayse et al. . 1995; ; Costello and Daane 1998c), ), and some growers and re­ searchers have observed lower leaf­ hopper numbers after the addition off a cover crop to some vineyards. Still, the role off cover crops in vineyard IPM is not well understood, and their use to t help manage leafhoppers rs -