A new species of parasitic wasp found attacking soybean gall midge

by Robert Koch (Associate Professor & Extension Entomologist), Gloria Melotto (Graduate Student, Entomology) and Amelia Lindsey (Assistant Professor, Entomology)

 

It is not very often that new species of insects are discovered in Midwest field crops. However, there has been some excitement lately among those who study soybean insects in the region. Our investigations into potential management options for the soybean gall midge have led to the discovery of a new species of parasitic wasp associated with this pest in Minnesota soybean fields. We recently published a scientific paper describing this species and giving it the scientific name Synopeas maximum.

Image 1: Adult parasitic wasp (Synopeas maximum) and soybean gall midge (SGM) larva on a penny for size reference (photo credit: Gloria Melotto).

Image 2: Close up of adult parasitic wasp (Synopeas maximum) (photo credit: Elijah Talamas)

In general, species in the genus Synopeas are tiny wasps that parasitize (feed on) a group of flies called gall midges, of which soybean gall midge is a member. These wasps lay their eggs into the eggs or larvae of the gall midges. After the wasp eggs hatch, the wasp larvae feed within and eventually kill the gall midge. Such wasps can be important for biological control of crop pests.

The “maximum” part of the new wasp's name builds on the names of soybean (Glycine max) and the soybean gall midge (Resseliella maxima). Because this species of wasp was so recently discovered, we still know very little about its biology and potential to control soybean gall midge populations. In additional research we confirmed that this wasp does indeed parasitize soybean gall midge and we’re exploring how its rates of parasitism of the soybean gall midge vary within fields and over the growing season.

The soybean gall midge itself a recently discovered species of pest attacking soybean in Minnesota, South Dakota, Iowa, Nebraska and Missouri. This pest can cause significant yield reductions to soybean (especially on field edges) and its known range is expanding in the Midwest. Unfortunately, management tactics for soybean gall midge remain limited, with insecticides providing relatively low and inconsistent levels of control. Our hope is that by improving the understanding of the parasitic wasps and other predatory insects that feed on soybean gall midge, we will be able to develop management recommendations for promoting populations of these beneficial insects in fields and the natural pest control they contribute.

 Additional collaborators on this research were Elijah Talamas (Florida Department of Agriculture and Consumer Services) and Jessica Awad (State Museum of Natural History, Stuttgart, Germany). This research was partially supported by the Minnesota Rapid Agricultural Response Fund.