Clearwing moths are a family of pests that attack many fruits trees, as well as currants and gooseberries. These pests are often mistaken for burly wasps.
There are several different clearwing moth pests and they attack a wide variety of ornamentals and edibles. They include:
Clearwing moth identification and lifecycle
One of the most obvious ways to identify adult clearwing moths is to look at their wings - they are clear. Mostly, anyway. Adults only live for one week, so you don’t get many chances to see them. Front wings tend to be narrow and rear wings are stubbier and wider. Their yellow and black bodies look similar to yellowjackets. This mimicry continues with a behavior commonly seen in wasps, in which both species will periodically run while fluttering their wings. Unlike wasps, clearwing moth adults can also be red, orange, or even dark blue, depending on the species.
As soon as females emerge from their pupal cases, they emit pheromones to attract males. After mating, females lay tiny pale pink to reddish eggs in rough areas of the bark, in wounds, and in cracks and crevices created where branches and twigs fork. One to four weeks later, larvae emerge and the damage begins. Clearwing larvae are 1” to 1-1/2” long, with white to pink bodies and dark heads. They look very similar to American plum borer larvae. Larvae will feed heavily until they are ready to pupate.
Most clearwing moths pupate under bark. The peachtree borer pupates in the soil. Clearwing pupal cases also look a lot like American plum borer pupae, as well as carpenterworm pupae. American plum borers (Euzophera semifuneralis) tend to be found where main scaffold branches join the trunks of ash, olive, and sycamore trees. These pupal cases are thin-walled and brown, and they look very similar to those of bark beetles, longhorned beetles, roundheaded wood borers, flatheaded wood borers, and metallic wood borers. These pupal cases are often found, after they have been vacated, protruding from bark or on the ground under a tree.
Basically, anything burrowing in your trees is bad news.
Damage caused by clearwing moths
Clearwing moth larvae start burrowing into bark, cambium or heartwood of their host tree as soon as they hatch. This burrowing creates galleries that weaken the tree and make it more susceptible to other pests and diseases. It also interrupts the flow of water and nutrients throughout the vascular tissues. Branch die off can also occur. All this burrowing can make bark look gnarled.
Where these galleries occur can help you identify the species. Peachtree borer larvae are most commonly found within a few inches of the soil. Ash borer larvae prefer being 5 to 10 feet up.
In some cases, no controls are needed. Sycamore borers and western poplar clearwings apparently don’t do enough harm to require management. The other species, however, can serious harm your trees.
Since healthy trees are better able to withstand attack, proper feeding and irrigation go a long way toward minimizing clearwing damage. Whitewashing tree trunks and exposed branches reduces sunburn injury. If your soil is compacted, apply a thick layer of mulch or install a ground cover to help aerate the soil. This will help keep your trees healthier, just make sure the mulch or ground cover are kept a few inches away from the trunk to prevent fungal disease. Also, avoid injuring trees with lawn mowers, weed wackers, and other landscape equipment and tools, and remove tree stakes as soon as they are no longer needed.
Pheromone lures can be used to monitor for these pests. Just keep in mind that using pheromone lures attracts pests. These lures interfere with mating, so they can reduce clearwing populations, but this method requires an intensive, ongoing program of pheromone use. It’s probably not worth the effort for backyard trees. You can also buy pheromone traps for peachtree borers and ash borers. If using pheromone traps, be sure to follow the manufacturer’s directions exactly.
Monitoring trees every week for signs of burrowing and pupal cases is an easy way to protect your trees. You may see partially emerged pupae, which can be crushed or skewered with a piece of wire. Gumming around the base of the tree may also indicate peachtree borers.
Beneficial insects, such as braconid wasps, will kill or parasitize clearwing moths and their larvae, so avoid using broad spectrum pesticides and insecticides. Also, you can buy certain nematodes (Steinernema carpocapsae and S. feltiae) to kill peachtree borer, redbelted clearwing, sycamore borer, and western poplar clearwing. Again, follow the directions exactly for the best results.
If a truly valuable tree has a bad clearwing infestation, you should call a licensed pest control applicator. They have access to chemicals that you do not. Most over-the-counter clearwing controls are not effective.
You can grow a surprising amount of food in your own yard. Ask me how!