by Mark Grundmeier, Soybean Product Manager
Recently, Iowa State University Extension Entomologist Dr. Erin Hodgson delivered a presentation about the spread in 2020 of Soybean Gall Midge (SGM) to 19 more counties across five Midwestern states.
To recap, SGM was identified in 2011 in soybean fields in eastern Nebraska. Then in 2015 and 2016, it was discovered in South Dakota and Iowa, respectively. Widespread damage from SGM wasn’t noted until 2018, and also that year SGM was found in Minnesota. In 2019, SGM was found in Missouri. The scientific name of Soybean Gall Midge is Resseliella maxima.
Scouting for this pest can be very difficult as it is only about 1/10 of an inch long. Focus on the edges of soybean fields, beginning in those areas where you may have seen SGM damage the previous year. Look in your earliest planted soybean fields that are at the V3 stage or later for wilted plants that at first glance look like a disease problem. Then carefully check the base of the plant, giving a slight push to the plant base to see if it will snap off. If it does, split the base of the plant with a knife and look for the orange or white larvae. If you find Soybean Gall Midge, please report this to your local Extension Agronomist. Extension personnel are very interested in tracking the spread of this significant new pest.
Because farmers in Nebraska, South Dakota, Iowa, Missouri and Minnesota have been sharing their findings of SGM, Dr. Hodgson said she and her colleagues are making observations on the insect’s life cycle. Eggs are laid in soybean fields at from 2 to 4 inches deep. These eggs overwinter and emerge as adults the following year, flying into nearby soybean fields that are at that V3 stage or later where they will mate and lay eggs in soybean plants that have a wound or opening. These eggs hatch inside the plant with a total of three instars that will develop and feed on the inside of the plant. The third instar will be the largest and will usually be orange in color. These will eventually drop off the plant and burrow into the soil to later hatch and produce adults. This entire life cycle can take just 28 to 32 days.
Managing Soybean Gall Midge has proven to be very difficult as the larva are well protected by the plant and the presence of adults is extremely widespread through out the growing season. One researcher in Nebraska noted that adults could be found anytime between six and eight weeks in fields. While insecticides will easily control SGM adults, the timing of application over that period would be costly and tedious.
If you farm in the Missouri River area, please watch closely for Soybean Gall Midge and report your findings to your local Extension personnel. I would also appreciate a “heads up,” so I can make some observations of my own.
