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.

Colorado potato beetle, Leptinotarsa decemlineata, wireworms and white grubs are important pests of potato that are challenging to manage. This study evaluated three endemic entomopathogenic nematodes (EPNs) (Steinernema carpocapsae 'NY01', S. feltiae 'NY04', and Heterorhabditis bacteriophora 'Oswego') as biocontrol agents against L. decemlineata, wireworms and white grubs in New York. The efficacy of individual EPN species and their combinations on L. decemlineata larval mortality was assessed via soil-based bioassays in the laboratory. Additionally, L. decemlineata survival and percentage of tubers damaged by wireworms and white grubs were evaluated in field trials in which combinations of pairs of EPN species were applied to the soil at least one month prior to initiating the experiment. Results from bioassays indicated that among the three EPN species, L. decemlineata late instars were most susceptible to H. bacteriophora 'Oswego'. Additionally, larval mortality was generally higher (14% on average) using pairs of EPN species compared to single species. Soil applications of pairs of EPN species prior to potato planting did not affect L. decemlineata adult survival either during the summer or following spring. However, tuber damage caused by wireworms and white grubs was reduced by 40% using a combination of H. bacteriophora 'Oswego' and S. feltiae 'NY04'. Overall, EPNs applied in soil have potential as biocontrol agents for soil-dwelling pests like wireworms and white grubs in potato, and their efficacy also may extend beyond a single cropping season, but do not seem to be an effective tool for L. decemlineata management in potato.