In South Dakota, a lot of soybean fields are naturally beginning to change colors as soybean senescence has started. This is going to greatly affect how we determine whether or not fields are infested with gall midge larvae.
We are still receiving confirmations of gall midge in South Dakota and the number of counties where this pest is present continues to increase. However, as soybean begins to senesce, using discoloration around field edges will no longer be viable for finding infestations.
Several soybean fields scouted in a number of counties have plants dying or dropping leaves prematurely and are being mistaken for early senescence. Close examination of these plants indicates that stem canker is causing the premature plant death.
While scouting fields for gall midge this week I have been noticing a lot of holes in soybean leaves. The majority of the defoliation is due to the second-generation bean leaf beetle adults.
Gall midge are still being found in more counties in South Dakota. However, as we previously mentioned not all of the fields that the gall midge larvae are found in are exhibiting clear signs of infestation.
We are continuing to confirm more counties where gall midge larvae are causing issues in soybean fields. While scouting this week, we have noticed a trend that soybean near groves or shelterbelts tend to have higher likelihood of being infested.
August is often the time of year when we often start to let our guard down when it comes to crop scouting. Unfortunately, many diseases in soybeans show up in the mid to late season.
Soybeans scouted last week were found with white mold and sudden death syndrome. These two diseases develop starting at the soybean flowering growth stage and can occur throughout the rest of the soybean growing season.
Last week, we mentioned that gall midge larvae are being found more frequently this year in soybean. We also noted that where they are present, they seem to be causing a lot of issues with soybean development.
Soybean aphid populations are continuing to persist and increase in South Dakota. Hot spots can be observed from the Southeast to the Northeast corners of the state. For this reason, scouting should continue and extra attention should be given to fields that are close to the 250 aphid/plant threshold.