Noteworthy observationsLarge aspen tortrix
Small, scattered pockets of defoliation caused by the large aspen tortrix caterpillars occurred along the north shore from Cook County to Duluth and down into Carlton and Pine Counties. Moths had already emerged by June 21st .
Forest tent caterpillar
Forest tent caterpillars can be found throughout northern Minnesota. In most cases, only scattered clumps of trees have been defoliated but, in a few cases, areas up to two square miles have heavy defoliation. Most feeding was finished with caterpillars starting to spin cocoons by June 21st . The moth flight and egg laying will occur the first part of July. With the adequate moisture we have been receiving, heavily defoliated trees should releaf nicely in July.
Birch leaf miner
The first generation was still mining leaves in Duluth as of June 21st .
Mt. ash sawfly
Voracious larvae of the first generation were 1/3 to 5/8 of an inch long on June 20th in Grand Rapids.
Pale green weevil
First sightings occurred in mid-June. Although they only feed on the edge of leaves, they can cause significant damage to berry foliage.
Oak wilt disease has become active across much of the southeast. We are seeing early signs of root graft infections from active centers. Local news releases have gone out, financial assistance is available for cost share practices. See section on Community Forest Health Grants.
Oaks recover from anthracnose outbreak
The cool, wet weather that set the environmental stage for an outbreak of oak anthracnose across much of southeastern Minnesota came to an end in late May. With improved weather conditions the oaks had time to recover. New disease free healthy foliage has developed on the trees and they are on the road to recovery. Recovery shouldn't be a problem this year given the excellent conditions were now experiencing in this region.