Landscape Message: Jun 10, 2016

Gypsy Moth:
Caterpillars are actively feeding on the leaves of hosts including oak
(mostly), maple, birch, poplar, willow, etc. Caterpillar numbers are
elevated in certain areas this year, corresponding to locations with
high numbers of egg masses laid last season. Therefore, caterpillar
presence is patchy across the landscape and not all locations are
experiencing high gypsy moth populations. Calls are flooding in,
describing caterpillars crawling over many outdoor surfaces: host tree
trunks, limbs, lawn furniture, patios, the sides of homes, sheds,
garages, etc. Spotted areas in towns including but not limited to
Sturbridge, Monson, Charlton, Northborough, Westborough, Plymouth,
Carver, Kingston, and Wareham are reporting frass (excrement) and
caterpillars "coating everything". Caterpillars are getting larger by
the minute, with many 3rd and 4th instars present. The heaviest feeding
from this insect will occur over the next few weeks, with caterpillars
growing ever larger until pupation begins in late June and early July.
Adult emergence will occur primarily in July when mating and egg-laying
will take place. At this point, Bacillus thuringiensis Kurstaki
may not be effective on larger caterpillars. The active ingredient
spinosad may be more effective at this time, however larger caterpillars
are more difficult to kill. This active ingredient should not be
applied to flowering plants as it is toxic to pollinators until it
dries. The continued hope is that the fungus, Entomophaga maimaiga, and
the NPV virus will catch up to the increasing populations of gypsy moth
in these areas and provide some relief. That remains to be seen.

Report by Tawny Simisky, Extension Entomologist, UMass Extension Landscape, Nursery, & Urban Forestry Program