Exploring the use of the sterile insect technique for navel orangeworm (Amyelois transitella) control in California. An update on recent progress

High value speciality tree nut crops such as almonds, pistachios and walnuts constitute a significant component of the total agricultural revenue for the state of California. Navel orangeworm (NOW), Amyelois transitella (Walker) is a primary pest of tree nuts reducing crop yield and quality. Furthermore, females can introduce spores of Aspergillus flavuswhich produce aflatoxin, a known human carcinogen, during oviposition. Thus, there is l ittle tolerance for their presence within the industry with most growers aiming for crop damage to be less than 2 %. Current integrated pest management (IPM) practices against this pest rely on 4 key tactics – good orchard sanitation, timely harvests, well-timed insecticide applications and mating disruption. Another control tactic under investigation is the sterile insect technique (SIT). SIT releases large numbers of sterile insects into a target area as part of an area-wide integrated pest management strategy and has been used to suppress or eradicate insect pests since the 1950s. Since 2016, efforts have been under way to adapt the former USDA-APHIS Phoenix pink bollworm facility to mass rear and irradiate NOW. Research to date has focused on the performance of mass reared NOW, including investigating the effects of irradiation, transportation and release methods on their competitiveness and flight capacity. Here we report on some of the developments that have occurred during the last 12 months including investigating the use of UAVs to release NOW aerially.