Now is the time for the arrival of azalea caterpillars for this year. Azalea caterpillars, Datana major, are among our most attractive caterpillar species. These are one of our largest and most colorful caterpillars. They are light green right after hatching. A little older and they get yellow and black stripes from head to tail. As they grow the caterpillars change from yellow with black stripes to black with yellow patches. The largest stages are shiny black with rows of yellow spots.
They feed primarily on Rhododendron spp. but they have also been found on blueberries. They do not feed on other plants in the landscape. There is one generation of this pest each year. Adults lay eggs on the underside of azalea leaves where the small caterpillars feed gregariously.
For such a bright creature they can be awful hard to see. The easiest way to find them is to look across the top of azalea bushes for twigs with no leaves. It will look like someone grabbed a twig in their fist and stripped all the leaves off. Once you find this feeding damage poke around and you will spot the caterpillars. Usually, these (and other caterpillars) are noticed by the damage rather than by noticing the actual critters or eggs. Thus, by the time they are noticed azalea caterpillars may have consumed a lot of foliage. Scout for these caterpillars by scanning shrubs for bare twigs then look closer to investigate. You may also see collections of frass on leaves that indicate caterpillars feeding. If you find a group of them just prune the branch out. Azalea caterpillars and many other species curl into a “C” shape when they are scared. This must scare off some predators but don’t be frightened. Azalea caterpillars don’t have any sharp spines or hairs (but they may regurgitate some yellow juice on your hand).
There is no reason to treat with an insecticide for this pest. On an average azalea, you could pick off and destroy all the caterpillars in few minutes. Plants can be pruned to remove damaged branches or branches full of caterpillars.
For more information on this or any gardening question call the Extension Master Gardeners Monday, Wednesday, or Friday from 1-3 PM at 252-237-0113 or email any time at firstname.lastname@example.org.