You may have noticed a massive influx of caterpillars this time of year. The cottony, spindly webs adorning your trees may look like they are cause by the same pest, but their inhabitants are very different. The webworm, bagworm and tent caterpillar all start their lives in similar thready nests. These webs act as protection and insulation. The eastern tent caterpillar creates a large woolly web in the crotch of tree branches. These webs become more prominent as the tree defoliates. The voracious caterpillars will commonly defoliate your deciduous trees in their entirety. While this is an unsightly problem, healthy trees with usually produce a new crop of leaves the following season. However, if the tree’s health was already compromised, this could prove detrimental to its overall health. Without its leaves, the tree is unable to produce energy, and it may become susceptible to other invasive pests or disease.
The eastern tent caterpillar will overwinter in masses of shiny, black eggs. Beginning in March, caterpillars will emerge and explore their surroundings. They may spin a web in a nearby crotch as a single group, or combine multiple webs into a large colony. The caterpillars use the protection of this web to regulate their temperature. During the heat or rain they may retreat from its surface, emerging at night when its cooler to feed. The caterpillars will emerge black and hairy, with a white or light colored stripe running down its back. It will also have brownish or yellow striping down its sides. Fully grown at 2-2 1/2 in, the caterpillar will spin its cocoon. In about 3 weeks time, the adult moth will emerge to lay the next generation’s eggs.
The webbing of the eastern tent caterpillar will protect them from pesticide sprays. Early intervention is crucial. Manual removal of the nests is very helpful for controlling the following year’s population. However, not all webs are easily accessible. As the webs form higher in the tree, and in greater numbers, reaching them becomes unsafe and is no longer practical. Contact your arborist to discuss management sprays. Our licensed arborists will contain the infestation before your tree becomes critically defoliated. So as always,