Forest tent caterpillars

Forest tent caterpillars are eating basswood leaves in Father Hennepin State Park, near Isle, and on an island in Borden Lake, just west of Lake Mille Lacs. Their numbers had increased in l997 so that defoliation of 70 to 90% of the deciduous trees occurred in June. This year, a May 8th check of the Isle population revealed larger numbers of caterpillars, many ¾ of an inch in length. They are still clustered on branch tip leaves, but will soon disperse and defoliate various deciduous trees. Heavy defoliation is predicted at both locations.

Typically this insect survives in detectable numbers in basswood stands around lakes. The l997 field surveys revealed only a few other forest tent caterpillar populations.