By Todd Lanigan, forest health specialist, Eau Claire, todd.lanigan@wisconsin.gov, 715-210-0150

Jack pine budworm, a native defoliator of jack pine and other conifers, caused defoliation of jack pine in the Town of Clearfield, Juneau County. Defoliation levels ranged from light to moderate, with some areas along roadways having higher levels of defoliation.

Jack pine trees defoliated by jack pine budworm.

The defoliation is mostly on jack pine and occurs between 32^nd and 35^th Streets along Highways 80 and 58. Defoliation also extends north past 32^nd Street, to 9^th Avenue in the west, and in the subdivisions east of Hwy 58 between 35^th and 32^nd Streets.

Most of the jack pine showed light to moderate defoliation. The open-grown jack pine along the edge of 32^nd and 35^th streets have the highest levels of defoliation. Jack pine budworm is a sun-loving insect, so defoliation along roadways is not unexpected. There was no evidence of defoliation in the adjacent red pine stand.

Jack pine needle closeup with hatched budworm egg mass (silver grey area).

An egg mass survey was conducted, and egg masses were found on jack pine needles. Based on the egg mass counts, there could be moderate defoliation to the jack pine in this area again next year. The severity of the defoliation will depend on how many jack pine budworm caterpillars survive the winter. Egg masses were also found in the adjacent red pine stand, so there may be some light defoliation there as well.