Nosema maddoxi (Microsporidia: Nosematidae) in brown marmorated stink bug, Halyomorpha halys (Hemiptera: Pentatomidae), populations in the United States

Abstract

In 2017, Nosema maddoxi Becnel, Solter, Hajek, Huang, Sanscrainte, & Estep (Microsporidia: Nosematidae) was described as a pathogen of the brown marmorated stink bug, Halyomorpha halys (Stål) (Hemiptera: Pentatomidae). This study focused on the phenology, distribution, and prevalence of N. maddoxi infections in H. halys populations in the United States. Collections of H. halys from three sites in 2018 were evaluated for the seasonality of N. maddoxi infections. Prevalence of infection in spring, after H. halys adults overwintered, averaged 37.5 ± 18.9% (peaking at 60.0% in one site) followed by lower infection prevalence during two summer collections (9.7 ± 4.1% and 7.3 ± 2.4%). Collections of H. halys from 31 sites in 11 states in 2017 and 2018 were evaluated and N. maddoxiwas found in every state sampled, averaging 18.9 ± 4.3% infection (range: 0.0–52.0%). Prevalence of low-intensity infections was higher than high-intensity infections in both the phenology study (low-intensity infections = 69.3%, high-intensity infection = 30.7%) and the distribution study (low-intensity infections = 62.4%, high-intensity infections = 37.6%). Internal melanized tissues within infected H. halys adults are visible as brown spots through the abdominal cuticle and this physical sign can help indicate N. maddoxi infection: 74.2% of H. halys with these spots were infected; however, 30.0% of H. halys adults that did not have spots were infected. Based on this study, this pathogen is widely distributed throughout H. halys populations in the US, and infection prevalence is variable among sites and is seasonal, with the highest infection levels occurring when H. halys adults are aggregated.