SD43: Proactively evaluating the biological control potential of a native predatory mirid against the South American tomato leaf miner

The South American tomato leafminer Pthorimaea absoluta (Lepidoptera: Gelechiidae) is a highly invasive and destructive tomato pest. Although it has yet to enter the United States, it has been prevalent in European tomato-growing regions for the past two decades, and an eventual U.S. invasion is considered likely. Insecticide application has been the primary control method employed against P. absoluta, but concerns about insecticide resistance and sub-lethal effects have driven the adoption of alternative control measures. In Europe, the use of predatory mirids (Hemiptera: Miridae) as biological control against P. absoluta has proven successful; however, these mirids are often phytophagous and may themselves cause damage to plants in the absence of suitable prey. Here, we seek to identify any native or introduced Californian mirid species that have the potential to control P. absoluta populations and investigate (1) their propensity for P. absoluta predation, and (2) their preference for P. absoluta compared to alternative prey options. One predatory mirid species, Engytatus varians, was consistently present across our sample sites during the 2023 and 2024 sampling seasons, and here we show via behavioral experiments that E. varians has the ability to consume P. absoluta and does so even in the presence of alternative prey. The results of this work will provide a framework for establishing proactive biological control procedures in the case of a P. absoluta invasion and will give insight into the distribution and behavior of novel predatory mirid populations in California.