Azalea caterpillars or Labor Day worms?
Published 4:17 pm Thursday, August 3, 2023
It’s that time of year again and the usual suspects are beginning to appear. Last week I went over a pest that we see this time of year that does detrimental damage to pecans. This week I am looking at another one. This very colorful worm (a.k.a. caterpillar) on your azaleas is an azalea caterpillar (Datana major). They are very destructive little critters! In large enough numbers, they can defoliate an entire bush. Often, they are not noticed until the damage is already done.
The azalea caterpillar hatches around mid to late-August, earning the name Labor Day worms. The eggs are on the underside of the leaf and packed in as a tight cluster of white eggs numbering 80 to 100. The eggs will hatch and the young caterpillars will emerge having a yellow body with black stripes and a red head. As they grow, they will molt to a black body with yellow dots, the red head may or may not, turn almost purple. The way to distinguish caterpillars from other insects, like sawflies, is by the three sets of legs near the head. The azalea caterpillar will raise its head and curl its tail when disturbed to form a shape like the letter “C”. There are a few others that do this but not many.
Upon eating their fill of your azalea, they will crawl down the plant and burrow into the soil to pupate. It is here that they will spend the winter. In late spring they will emerge as adult moths and begin the process all over again. Do not worry about handling these caterpillars, they are completely safe. They may however, regurgitate yellow juice onto your hand.
In a homeowner situation it is really best to pick the caterpillars off of the bush and smash them or place them in a bucket of soapy water. You can pick them off by hand if there are just a few or, you can shake the bush to remove them. If the infestation is really bad, you may need to go to a product containing B.t. (Bacillus thuringiensis). This is a natural, organic product that will control the young caterpillars. It is marketed under names such as DiPel. Spinosad is another organic approved insecticide that will work on caterpillars and some beetles. There are insecticides that will work such as Carbaryl (Sevin), Acephate (Orthene), and pyrethrin-based insecticides that end in -thrin. These insecticides are much more harmful to the beneficial insects on the bush, so beware of aphid or spider-mite spikes after using an insecticide. This is due to killing all of the beneficial insects that are predators of these pests.
Azalea caterpillars will only feed on rhododendron species for the most part. There has been documentation of feeding on blueberries however. So, if you have other azaleas, rhododendrons, or blueberries be sure to check them all.
NC State Extension provides unbiased, research-based, University information to you the consumer or producer. If you have not visited your local Cooperative Extension Center, you may be pleasantly surprised by all of the information, workshops, and programming we offer! We will have a fall veggie class coming up on September 9th and veggie sale on Saturday September 16th, call our office or look on the Beaufort County Master Gardeners Facebook page for more information. If you are interested in the Extension Master GardenerSMVolunteer (EMGV’s) program training, now is the time to call our office or visit the website (beaufort.ces.ncsu.edu) for more information. We will be having a training that will begin in the latter part of September. We will meet on Tuesdays at the Beaufort County Center from 9:00-12:00 beginning on Tuesday September 19th. If you are interested, please send in your application.
If you have a question to submit, please email to Gene Fox at firstname.lastname@example.org. Having trouble with growing in your home landscape, call the Extension office and speak to an Extension Master GardenerSM Volunteer Greenline, Mondays and Wednesdays between 10:00 and 12:00 at (252)946-0111.