Advanced control of codling moth (Cydia pomonella) using the beneficial nematode Steinernema carpocapsae in apple and pear orchards in the Pacific North West

The most significant insect pest in apple and pear trees in the Pacific Northwest (PNW), USA is the codling moth (Cydia pomonella). In the PNW, codling moths generally produce 2-3 generations per year, but have been observed to produce up to 5 generations in some hot spots. During early larval stages, codling moth larvae burrow into apples and feed on the fruit, resulting in lost crops and lost income for growers. Growers have limited options for controlling this pest at the larval stage. This challenge is compounded for growers maintaining an organic orchard. Few biological control options are available, and the ones currently on the market tend to target 1st instar larvae and adults. A promising means of decreasing codling moth populations is entomopathogenic nematodes (EPNs), specifically the species Steinernema carpocapsae, which was originally isolated from codling moth larvae. These microscopic round worms, also known as beneficial nematodes, can fill in the gap left by other biocontrol agents, by attacking the mature and overwintering larvae in the soil and the base of tree trunks. A few years ago, successful trials were conducted in apple orchards in Germany and the United Kingdom, where beneficial nematodes reduced fruit damage by nearly 75%. In 2019, field trials in the PNW during spring, summer, and fall resulted in codling moth larvae mortality of 89%, 74%, and 90% respectively. Results demonstrated that beneficial nematodes are a powerful tool for apple growers to incorporate into an integrated pest management system.