Defoliation by larch casebearers

By Linda Williams, forest health specialist, Woodruff, (Linda.Williams@wisconsin.gov), 715-356-5211 x232

The two cigar-shaped, tan objects sticking to the newly expanding needles of this tamarack tree are larch casebearer caterpillars, feeding on the foliage.

The two cigar-shaped, tan objects sticking to the newly expanding needles of this tamarack tree are larch casebearer caterpillars, feeding on the foliage. Photo: Linda Williams

As tamarack needles begin to appear, so do some tiny caterpillars that feed on them. Larch casebearers defoliate tamarack trees early in the season, first causing the trees to look pale green or yellowish, or even brown if defoliation is severe. This year I have been able to find larch casebearers wherever I look, but so far, I haven’t found any high populations of the insect.

To look for larch casebearers, you’ll need to get close to the tamarack and look for small,  cigar-shaped, tan objects attached to the needles. If you look closely, you’ll see a head and tiny legs sticking out of one end of the “cigar”. If you see areas of tamarack being heavily defoliated this year, please let your forest health specialist know. Defoliated trees usually send out a second set of needles in July.

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