Integrating Trissolcus japonicus into management programs for Halyomorpha halys in apple orchards: impact of insecticide applications and spray patterns

Authors: LUDWICK, DALTON - Texas A&M Agrilife; PATTERSON, JESSICA - Shepherd University; LEAKE, LAYNE - University Of Missouri; Carper, Garland - Lee; Leskey, Tracy

Submitted to: Insects
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/20/2020
Publication Date: 11/26/2020
Citation: Ludwick, D.C., Patterson, J., Leake, L.B., Carper Jr, G.L., Leskey, T.C. 2020. Integrating Trissolcus japonicus into management programs for Halyomorpha halys in apple orchards: impact of insecticide applications and spray patterns. Insects. https://doi.org/10.3390/insects11120833.
DOI: https://doi.org/10.3390/insects11120833

Interpretive Summary: The brown marmorated stink bug (BMSB) is an invasive species in the United States that has caused severe damage to tree fruit, including apples. In 2014, an Asian egg parasitoid, the Samurai wasp, was discovered in the mid-Atlantic. Since that time, it has spread throughout a number of states including West Virginia. Here, we evaluated how best to integrate the Samurai wasp into management programs for BMSB. We found that some insecticides, particularly bifenthrin, affected adult wasp survivorship, and emergence from parasitize egg masses was affected by this compound as well as thiamethoxam + '-cyhalothrin, and methomyl. Eggs parasitized 2- and 7-days prior to an insecticide were less affected. Ultimately, using sustainable approaches such as border row and alternate row-middle spray application patterns provided unsprayed refugia for developing Samurai wasp in parasitized eggs, enabling greater emergence. Our results indicate that the Samurai wasp will have greater impacts in orchards that practice integrated pest management, enabling more wasps to be present and foraging for BMSB egg masses, likely leading to reductions in stink bug populations across the landscape.

Technical Abstract: Halyomorpha halys (Stål) (brown marmorated stink bug; Hemiptera: Pentatomidae) is an invasive species in the United States where it has caused significant damage to specialty crops, including apples. In 2014, an Asian egg parasitoid of H. halys, Trissolcus japonicus Ashmead (Hymenoptera: Scelionidae), was discovered in the United States with adventive populations now present in a number of states. While integrated pest management (IPM) techniques have been developed for H. halys in apple, including spray application techniques, it is unknown how they affect foraging T. japonicus and its offspring. In this study, egg masses (unparasitized and those parasitized 2- and 7-days by T. japonicus prior to the insecticide treatment) were placed in apple orchards in treated and untreated locations receiving conventional full block insecticide applications or reduced application techniques, including border row or alternate row middle applications. Materials evaluated included bifenthrin, thiamethoxam + '-cyhalothrin, clothianidin and methomyl. Egg masses were retrieved 24 hours after spray applications. For 2- and 7-day parasitized treatments, emergence of adult T. japonicus was recorded from each egg mass. For unparasitized egg masses, T. japonicus females were given 24 hours to forage and oviposit on post-treatment egg masses with female survivorship adult emergence from egg masses 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 + '-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.