Evaluating the use of predatory plant bugs (Hemiptera: Miridae) as biological control against the invasive South American tomato leafminer (Tuta absoluta) in California tomato fields

The South American tomato leafminer Tuta absoluta (Lepidoptera: Gelechiidae, now Phthorimaea absoluta) 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 T. 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 T. 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 T. absoluta populations and investigate (1) their preference for T. absoluta compared to alternative prey options, (2) their potential to cause damage to host plants, and (3) the factors influencing their spatial and temporal distribution throughout the growing season. One predatory mirid species, Engytatus varians, was consistently present across our sample sites in the first of two sampling seasons, and behavioral experiments to determine its biological control potential, as well as continued sampling, are ongoing in the 2024 growing season. The results of this work will lay the foundation for proactive biological control procedures in the case of an eventual T. absoluta invasion in the U.S.