Spatial and temporal dynamics of soybean gall midge (Resseliella maxima) parasitism by Synopeas maximum

BACKGROUNDSoybean gall midge, Resseliella maxima Gagne (Diptera: Cecidomyiidae), is a pest that impacts soybean yield in the Midwest United States. While biological control using parasitoids may be a promising approach for managing this pest, it is crucial to have a deep understanding of parasitism dynamics to ensure effective implementation. We investigated R. maxima parasitism using a combination of three methods: rearing of field-collected hosts, dissection, and molecular assays.RESULTSWe confirmed parasitism of R. maxima by the recently described wasp Synopeas maximum Awad & Talamas (Hymenoptera: Platygastridae) and used our combinatorial approach to observe the spatial and temporal relationships between R. maxima and its parasitoid in the field. The number of R. maxima adults was greater in symptomatic plants on field edges than the field interior, but such a pattern was inconsistent for parasitism rates. Parasitism rates were generally highest early and late in the season, and lower in the middle of the season when the number of R. maxima was highest.CONCLUSIONIn Minnesota, overall season-long parasitism rates of R. maxima were low (< 2%). To facilitate a wider investigation of the biological control of R. maxima, we designed a protocol for high throughput DNA extraction and quantitative polymerase chain reaction (qPCR) that can be used across a broader geography. Further research should evaluate how parasitism rates by Synopeas maximum could be promoted in production fields. (C) 2023 Society of Chemical Industry.

Automated summary

The study investigated the relationship between soybean gall midge and its parasitoid using a combination of methods. It was found that parasitism rates of the midge varied seasonally and were generally low. To facilitate further research on biological control of the midge, a protocol for high throughput DNA extraction and qPCR was designed.