Mulching Effects on Nutrient Contents of Potato Foliage and Colorado Potato Beetle Fitness.

Application of organic mulches has repeatedly been shown to reduce infestation with Leptinotarsa decemlineata (Say) (Coleoptera: Chrysomelidae), the Colorado potato beetle (CPB). In order to determine if the nutritional status of potatoes as affected by mulch could explain the mulch effects in potatoes against CPB, we determined potato leaf nutrient composition in unmulched control plots and plots mulched with grass-clover or triticale-vetch and assessed mulch effects on CPB damage and development in the field during 3 years and under controlled conditions. In mulched plots, foliar Mo, Cl, and K contents were consistently higher than those without mulch, and leaf damage by CPB was reduced significantly. In addition, increased B contents were associated with undamaged plant material, while higher Zn contents were associated with leaves damaged by CPB. Under controlled conditions, CPB fitness was not affected by mulch application. Overall, reduced CPB damage could not be clearly attributed to altered foliar nutrient contents due to mulching. It is thus more likely that CPB reductions in mulched systems are due to mechanisms other than an altered nutrient balance.