I received an e-mail message yesterday from our "BYGL Early Warning System" (a.k.a. Larry Hanks, Pampered Properties, Lexington, KY) reporting that overwintered eastern tent caterpillar (ETC) (Malacosoma americanum) moth eggs began hatching yesterday afternoon in Georgetown (Scott County), KY. Larry has been reporting his egg-hatch observations for around 20 years and this is the earliest he has ever observed this important life-cycle event.
ETC spends the winter in shiny, blackish-brown egg masses wrapped around twigs on their host plants. A close examination will reveal that the eggs are encased in a structure that resembles bubble-wrap. The accumulated Growing Degree Days (GDD) that predicts ETC egg hatch is 92 and full bloom of Callery pears is a pretty good phenological indicator. Pears are blooming in Greater Cincinnati; however, I have not yet seen egg hatch in our part of the state. We are currently experiencing a dramatic dip in temperatures that's forecast to last through much of next week. I don't know what effect this will have on egg-hatch or the caterpillars.
ETC caterpillars are accomplished and prolific tent-makers producing highly visible silk nests in the forks of branches. They begin producing silk nests immediately upon hatching from eggs. Look closely for the tiny, hairy first instar caterpillars clinging to small, silk nests that surround their egg mass. The caterpillars prefer to feed on trees in the family Rosaceae, particularly those in the genus Prunus, such as cherries. They also occasionally feed on ash, birch, maple, and oaks. The caterpillars are covered in short; grayish-white hairs and they have a distinct, unbroken white stripe down their backs.
The caterpillars are capable of causing serious stress to their host trees; newly planted trees are particularly vulnerable. Leaves lost to caterpillar feeding this spring must be replaced using energy stored from last season. Small nests can be eliminated digitally using five-fingered "smash and/or smear" techniques. Less hands-on methods include applications of the naturally occurring bacterium, Bacillus thuringiensis (Bt), applied to early instar stages, as well as standard insecticides labeled for general caterpillar.