Transmission and Vectoring of Fusarium spp. and Aspergillus spp. by Brown Marmorated Stink Bugs (Hemiptera: Pentatomidae) in Zea mays

Brown marmorated stink bugs (BMSBs) (Halyomorpha halys) are an invasive and highly polyphagous species native to Asia that was first detected in Allentown, Pennsylvania in 1997. Corn losses from stink bug feeding are mostly quality losses, mainly aborted kernels and malformed ears. Aspergillus flavus and Fusarium verticillioides are two plant pathogens that negatively impact Mid-South corn. A biological feeding assay, a corn kernel plating assay and a quantitative mycotoxin test from an ear caging field corn trial, and Mid-South stink bug collection survey were conducted. The objectives of these investigations were to determine if BMSBs can pass mycotoxigenic spores internally, if increased stink bug feeding causes increased pathogen presence and mycotoxin levels in field corn, and if this is an issue across the Mid-South. In the bioassay, results revealed that BMSBs can pass mycotoxigenic spores through their digestive system, but very minimally and are most likely being vectored externally. For the ear caging experiment, the corn kernel assay determined more Fusarium spp. colonies grew out compared to Aspergillus spp. colonies, but mycotoxin quantification revealed that fumonisin was the dominant mycotoxin in 2022 and aflatoxin was dominant in 2023. A statistically significant interaction between trial and treatment did exist for fumonisin and aflatoxin indicating environmental conditions, infestation timings and pathogen competition are the most likely reasons for the mycotoxin trends. The Mid-South survey required out-of-state cooperators to collect 25 stink bugs of the same species. In 2022, high numbers of Fusarium spp. and Aspergillus spp. were recovered from stink bug frass but saw sharp declines in both pathogens in 2023. Collection substrate, weather conditions and harvest timing likely contributed to the sharp decline in pathogen presence. From both the feeding bioassay and survey, it was found that BMSBs can minimally internally vector plant pathogens, meaning spores are most likely being vectored externally. From the ear caging experiment, increasing numbers of stink bugs were not statistically significant for increasing mycotoxin levels because the environmental effects heavily influenced pathogen and mycotoxin development in the field. The Mid-South survey had inconclusive results, however it does provide more opportunities for additional research in this phenomenon.