Minnesota Plant Pest Survey Results

The following observations and maps have been made available courtesy of the Minnesota Department of Agriculture. To access the entire Minnesota Pest Report newsletter go to http://www.mda.state.mn.us/pestsurvey/pestreports/pestreport.html

Soybean Aphid Watch

Soybean aphid numbers continue to increase slowly. Aphids appear to be increasing primarily in southeastern Minnesota where fields are now commonly found with 25 - 50% of plants infested with aphids. However, very few plants have been found with more than 100 aphids per plant, even in fields with the majority of plants infested. No fields sampled by the MDA in 2004 have been anywhere near economic levels (250 aphids/plant on 80% of plants). Moreover, soybeans are completing pod set throughout southern Minnesota.

Bean Leaf Beetle

Bean leaf beetle numbers were generally low this week with the exception of a field in Washington County (EC) where 120 beetles were found in 30 sweeps. The field in Washington County was responsible for much of the increase in the statewide bean leaf beetle average this week though even with that field omitted the average climbed to 2.8 beetles per 30 sweeps. Bean leaf beetle should only be a concern if damage is occurring to pods or if significant defoliation is occurring.

Grasshoppers in Soybean

Relatively high numbers of grasshoppers can be found in a few soybean fields but generally numbers are not high. The greatest incidence of defoliation damage can be found in southern Minnesota where in many fields the majority of plants have some defoliation. However, in only two fields (Lincoln County - SW) was the severity of the defoliation rated as greater than 25% (i.e., the average plant in the field had greater than 25% of the leaf surface defoliated). The source of defoliation is not determined in these ratings.

Few European Corn Borer in NW

Some univoltine European corn borer have appeared in the NW, but numbers are low with < 50 % of plants damaged in all sampled fields. Corn ears are becoming noticeable in the south as plants reach the blister stage of development.

Corn Rootworm Numbers Steady