We continue to rate the General Condition of sugar maple by an annual evaluation of 2000 trees. Defoliation by the forest tent caterpillar has adversely affected tree health in some regions. For the first time in a decade, less than 90%
of sugar maple trees were healthy on our survey plots.

Forest Tent Caterpillar populations increased in 2006, with 343,000 acres of defoliation mapped by aerial survey. The damage generally increased from 2005 in southern Vermont and in the central Green Mountains, and decreased in the Champlain Valley.

Large numbers of caterpillars died from disease. Many others died in cocoons thanks to parasites, such as the native“friendly flies” that were so common in early summer. Still, the outbreak may continue in 2007.

Forest tent caterpillar moth counts are about the same as they were in 2005. In winter 2005-06, 209 sugarbushes were surveyed for forest tent caterpillar egg masses. Defoliation was redicted in two-thirds of them.

Although healthy maples can withstand several years of defoliation, some are declining in sugarbushes which have been defoliated two or three times. Dead trees are showing up in recently thinned sugarbushes, or on ridges, dry slopes or wet areas. Some unthinned trees on good sites have also died.

Saddled Prominent populations increased noticeably in the northern Vermont region which has not been affected by forest tent caterpillar. Defoliation was mapped on 1,340 acres in Essex, Orleans, and Caledonia Counties. Saddled prominent caused a lot of sugar maple dieback in the early 1980s. It does most of its feeding in July. Sampling in the spring can help predict whether or not the insect may be a problem.

The foliage of many sugar maple trees turned brown in September because they had been infected with the fungus disease, Anthracnose. Leaves were infected during earlier wet weather. Damage was worse on lower branches,
near wetlands and low-lying areas. The impact on tree health shouldn’t be serious, since the damage occurred so
late in the season.

Most Lecanium Scale populations crashed. Scattered sugarbushes still had a lot of these insects in 2006, with their honeydew and associated sooty mold. Sugar maple tree recovery seems good in areas with a lot of scale in 2005.

Weather Conditions continued to be good for sugar maple in 2006: a mild winter, no late frosts, plenty of rain, and
a warm fall. The rain had an upside…it helped trees recover from defoliation.

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