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Oakworms

Two oak defoliators, orangestriped and pinkstriped oakworms, have caused scattered, heavy defoliation of white oaks and intermingled birch in Benton, Crow Wing, Morrison and Todd Counties during mid- to late-July.

Since oaks have set their buds for next year, tree stress will be minimal. The adult stages of these two defoliators are moths. A sharp increase in their numbers was observed in 1997. Parasites and predators generally help to terminate outbreaks, but field observations allow the prediction that these pests will cause heavy defoliation in l999 in Benton, Crow Wing and Todd Counties.

Two-lined chestnut borer

The "Oak Decline Saga" continues to be the I&D challenge of most concern in Region I during the 1998 season. New pockets of infested trees have been observed in Detroit Lakes. Bur oaks appear to be the targeted host trees now that the large red oaks have declined. The two-lined chestnut borer causes girdling of the crown branches and tree trunk. Look for leaf browning with or without wilting symptoms, starting first in one or two upper crown branches that eventually spreads to the rest of the tree. Years of repeated environmental stress intermixed with anthracnose, aphids and other agents of foliar loss can lead to attacks by TLCB. Especially affected are trees growing on high, droughty soils. Armillaria root rot is commonly found on declining trees. If you suspect TLCB in your oak trees, contact your local DNR Forester to get adequate information about prognosis and management guidelines for TLCB.