Evaluation of endemic entomopathogenic nematodes for managing Colorado potato beetle and tuber-damaging pests in potato

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.