SDSU Extension publishes the South Dakota Pest & Crop Newsletter to provide growers, producers, crop consultants, and others involved in crop production with timely news pertinent to management of pests, diseases, and weeds in South Dakota.
A few corn fields scouted in Brookings County were found with Fusarium root rot at low levels. Infected plants were wilting and upon splitting of the lower nodes revealed brown discoloration of the pith. Root and crown rots developing in corn after the seedling stage are usually caused by Fusarium spp. and can be enhanced by injury to the roots or crown, mainly by insect feeding.
This week we observed some true armyworm caterpillars in winter wheat fields. The caterpillars were still relatively small, which means they will continue feeding for some time. So far, the true armyworm caterpillars were still feeding on the leaves of the nearly mature wheat, but they have the potential to also clip heads off of the plants.
Several soybean fields scouted the week of July 15, 2019 were found with bacterial blight developing. The frequent rains experienced in most soybean growing counties have led to the development of this disease. Bacterial blight affected leaves are most evident on younger leaves in the upper canopy.
While looking at winter wheat at the new SDSU West River Research Farm near Sturgis, we came across some very large stinkbug populations in a few areas of the field. The stinkbugs we observed were the Say’s stinkbugs. Although stinkbugs have the potential to reduce wheat yields, this is attributed with feeding that occurs between the late boot and milk stage.
In South Dakota, one of the insects that is commonly observed in sunflower is the Dectes stem borer larva. At this point in the season, adults are beginning to become active with females laying eggs in sunflower plants.
Soybean gall midge have been reported in three counties in South Dakota in the past week: Clay, Union and Lincoln. Scouting for soybean gall midge can be as simple as finding wilting or dying plants along the edge of the field, or it can be rather difficult if the plants are currently asymptomatic.
Earlier this year, we observed a large emergence of overwintering bean leaf beetles throughout much of the state. We are again observing quite a few bean leaf beetles beginning to emerge. These emerging beetles are the result of overwintering beetles mating and laying eggs.
Tweets about European corn borer (Ostrinia nubilalis) caterpillars in the stems of conventional corn and feeding in the whorls of corn are crossing my Twitter feed. Unfortunately, there is a problem with some of these tweets. Not all of the caterpillars that are being identified as European corn borer caterpillars are actually European corn borer caterpillars!
While scouting soybean this week I noticed quite a few defoliating insects that were present in the field. So far, the feeding injury is minimal, but it is a reminder that we need to be diligent in monitoring leaves for defoliation and fields for these insect pests.