Late season tree defoliators

A fall web worm will defoliate a tree in the fall, when a tree has already stored energy in its root system, doing much less damage than spring defoliators. There are a number of insects that consume tree leaves during the late summer and fall in our area.

Some of the more common varieties are the fall webworm, an insect that builds webs in trees in August and September, and the orange-striped oakworm, a fairly large caterpillar that congregates in large numbers on the ends of oak tree branches, consuming the host tree’s leaves.

Fall webworm (moth)

(Hyphantria cunea)
Credit: - Robert Webster

While unsightly, these insects usually do not harm large deciduous trees, although they could harm smaller trees, especially those trees that are newly planted.

Deciduous trees are those varieties that grow leaves in the spring and drop them in the fall. The advantage to this growth pattern is that the trees actively grow during the spring and summer, when conditions are favorable, and go into dormancy when it becomes cold outside.

This growth pattern also helps protect the plants from insects and other animals that would feed on their leaves during the dormant season.

The disadvantage of deciduous growth is that it requires large energy expenditure for the plant to create new leaves in the spring. For this reason, insects that defoliate trees in the early part of the season such as the gypsy moth, forest tent caterpillar and oak cankerworm can severely impact the health of a tree.

Late-season defoliators, on the other hand, attack a tree after it has already had a chance to grow and store energy in its root system to refoliate next spring, therefore not really impacting the health of the tree.

Article by FCFCDB member

Nature Notes for 9/27/2015