What’s that caterpillar hanging from the tree?
Your clients may be asking you about these critters. They are the larvae (caterpillars) of either oak leafrollers or oak leaftiers, two different species of moth. Leafrollers are from the genus Archips and leaftiers are from the genus Croesia.
This larval or caterpillar stage is one part of the moth’s life cycle. The adult stage is a yellow to light tan colored moth with a wingspan of 12-25 mm. Moths lay their eggs on the small branches of host trees in the late spring. These eggs hatch early the following spring when the oak leaves began to grow. Larvae feed and grow for about one month and then drop to the ground to pupate. Moths emerge within two weeks. Females live for a few days and lay up to 100 eggs. Then we see nothing more of these insects until the following spring.
What is important about them? They can cause widespread and severe defoliation (loss of leaves) of the trees they feed upon, but this rarely happens in Florida. The common scenario is several years of light to moderate defoliation, then insect populations collapse and we are unaware of these insects for a number of years. They can also be a nuisance to humans, but they are harmless.
Is there any control for the caterpillar? Natural controls (predators, parasites and diseases) usually keep these caterpillar populations at low levels. Mockingbirds and other birds feed on the caterpillars, and wasps appear to be the best control. For high-value trees or where caterpillar populations are especially damaging try using a biological control spray of Bacillus thuringiensis var. kurstaki. An insecticidal spray containing carbaryl (Sevin®) can be used as a last resort (this should be applied by a pest control operator). The ideal time for applying an insecticide is just before the insects begin their last week of voracious (heavy) feeding.