Integrating trissolcus japonicus (Ashmead, 1904) (hymenoptera: Scelionidae) into management programs for halyomorpha halys (stål, 1855) (hemiptera: Pentatomidae) in apple orchards: Impact of insecticide applications and spray patterns

Abstract

Halyomorpha halys (Stål, 1855) (Hemiptera: Pentatomidae) is an invasive species in the United States, where it has caused significant damage to specialty crops, including apples. While integrated pest management techniques have been developed for H. halys in apple, including spray application techniques, it is unknown how these techniques affect foraging, adventive Trissolcus japonicus (Ashmead, 1904) (Hymenoptera: Scelionidae), and its offspring. In this study, egg masses (unparasitized and 2 and 7 day parasitized pre-treatment) were placed in apple orchards in treated and untreated locations that received full block insecticide applications or reduced application techniques, including border row or alternate row middle applications. Bifenthrin, thiamethoxam + λ-cyhalothrin, clothianidin, and methomyl were evaluated. Egg masses were retrieved 24 h after spray applications. For 2 and 7 day parasitized pre-treatment, adult T. japonicus emergence was recorded from each egg mass. For unparasitized egg masses, T. japonicus females were given 24 h to forage and oviposit on post-treatment egg masses with female survivorship, and adult emergence from egg masses was recorded. Female survivorship was significantly lower on post-treatment egg masses retrieved from areas receiving bifenthrin applications. Emergence from post-treatment egg masses was affected by thiamethoxam + λ-cyhalothrin, bifenthrin, and methomyl in some treated areas, whereas less impact was observed on 2 and 7 day pre-treatment parasitized egg masses in general. These data provide further insights into H. halys management and the potential impact of T. japonicus in sprayed orchard agroecosystems.