Scouting for second generation eggs should have either begun late last week or early this week. In general, second generation corn borer damage is reported as low across the Midwest this summer. Spider Mites Reports of spider mite damage are coming in from nearby states and from across Michigan. Drier areas are more susceptible to spider mite infestation and damage, and while some of the state has had adequate rain, other areas have not. Mites suck the contents out of plant cells, causing the yellowing of leaves, and in more severe cases, the browning or bronzing of foliage.
Infestations often start on dusty edges of fields.
It is thought that dust dries the leaf surface, protecting mites from disease, or that the dust helps provide a surface for the mites to anchor their webs. Whatever the case, if an infestation is identified early, spot treatments may be enough. A heavy rain may reduce the population a little, but don't depend on rain alone. The real key is high humidity, since pathogens that kill mites require high, sustained humidity to grow and spread through the population. A heavy rain followed by quick drying does not provide a long enough period for the diseases to spread and kill a significant portion of the mite population.