Elucidating factors to improve biological control of Halyomorpha halys by egg parasitoids

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Halyomorpha halys Stål (Hemiptera: Pentatomidae), also known as the brown marmorated stink bug, is an invasive species from Northeast Asia, which has now spread to 47 USA states and invaded several other countries. In the USA, H. halys is an economically important pest of fruit, vegetable, field, and nut crops, and it feeds on ornamental plants. A sustainable means of controlling this pest is needed. Here I focus on elucidating features from bottom-up forces (alternate host identity, host plant identity, and habitat type) which may influence top-down forces such as parasitism by H. haly’s key natural enemies, Hymenoptera egg parasitoids. Naturally laid eggs of insects were collected from a tree nursery in 2020 and from diverse habitats throughout Maryland in 2021 to investigate H. halys parasitoids’ alternate insect egg hosts, host plant and habitat associations, and which factor(s) (host plant identity and/or host egg identity) are important to egg mass discovery, or to egg parasitism rate. Effects of host insect feeding guild (herbivore vs predator) and host plant origin (native vs non-native) on parasitism were also examined. One new overwintering insect host and four new in season hosts for Anastatus spp., and five new in season hosts for Telenomus cristatus were found. A diverse array of plant species, particularly native Acer and Quercus species, were found to support alternate host insects. Halyomorpha halys related parasitoids were reared from eggs collected in all habitat types. Host egg order and egg feeding guild affected Anastatus spp. egg unit discovery efficiency and egg parasitism rate. Host plant identity and plant origin affected egg unit discovery efficiency and egg parasitism rate by all H. halys parasitoids. These findings support the importance of having a diverse community of alternate prey and informed plant selections to support parasitoids and their biological control of H. halys and other insect pests.