Relatively new to the United States, the European pepper moth is poised to cause significant damage to gardens and commercial agriculture.
Each time an invasive plant or pest is brought into an area, there’s no telling what might happen. Resident predators or local diseases may make short work of the interloper. Then again, the insurgent may find a rich, predator-free environment perfectly suited to a population explosion. We don’t know, yet, which way things will go for the European pepper moth, but it’s probably a good idea to know what we’re up against, just in case.
Plants damaged by European pepper moths
It’s difficult to get excited about something that hasn’t directly caused damage in your garden, so here’s the list of just some of the plants harmed by the pepper moth:
If that list doesn’t get your attention, I don’t know what will. Also on the list of favorite foods are roses, African daisies, azaleas, orchids, and many other flowers and ornamentals.
Damage caused by pepper moths
The moths themselves don’t cause any harm to plants. Like other moths and butterflies, it is the larval stage, or caterpillar, that feeds voraciously on leaves, roots, buds, fruit, and flowers. Pepper moth caterpillars may girdle young seedlings, causing what looks like damping off disease. Later larval instars may burrow into stems unnoticed, until the the stem collapses. Leaf damage starts out looking crescent-shaped, similar to damage by the Fuller rose beetle, or round, but the entire leaf ends up being eaten. Feeding is normally seen in the lower leaves, then moving up the plant until it is completed defoliated. Feeding on the roots can interfere with a plant’s overall health and vigor and feeding on buds, flowers, and fruit, well, there goes your crop. So, what does the European pepper moth look like?
Pepper moth identification and lifecycle
Also known as the European marsh pyralid, adult pepper moths (Duponchelia fovealis) have a wingspan of approximately three-quarters of an inch wide and a body less than half an inch long. The forewings are grayish-brown with two distinct yellowish-white transverse lines. The outermost line has a “finger” that points backwards.
At rest, the pepper moth holds its wings out to either side in a triangular shape. The head, body, and antennae are olive brown, and the abdomen features cream-colored rings. Legs are pale brown. Both sexes have long abdomens, but the male’s is unusually long, and he holds his curved upwards at rest.
Pepper moth eggs are really tiny (1/50 of an inch). The eggs start out whitish green or pale yellow, which turn pink, then red, as they mature. Just before hatching, the egg turns brown. Eggs are laid singly or in batches on the underside of leaves, normally near the leaf veins. Eggs can also be found on stems, at the crown, in the soil, on the tops of leaves, and even on greenhouse walls and furnishings.
Caterpillars start out salmon pink with a black head, and a line of grey and brown spots along each side. Some sections may feature a double row of dots. Using a hand lens, you can see a hair emerging from each spot. Just behind the head, you can also see a hard plate, which is the same color as the head. As they grow, the pink turns a dirty white color that can range from pure white to pale or even dark brown, depending on which of your garden plants they are eating.
These caterpillars can grow to over an inch long. Just before pupating, they may lose their spots. Pepper moth caterpillars create a cocoon out of soil, frass, and webbing. The cocoon can be 1/2 to 3/4 of an inch long.
A single female pepper moth can lay up to 200 eggs. Under optimal conditions (temperatures around 68°F), those eggs can hatch in 4 to 9 days. Over the next 3 or 4 weeks, the caterpillars feed ravenously. Then, pupation takes 1 or 2 weeks. Adult moths live to mate and procreate for a week or two and the whole process beings again. In greenhouse environments, 8 or 9 generations a year can occur. That ends up being a lot of pepper moths! In areas like California, where cold winters rarely occur, this pest could prove to be devastating.
These moths have an unusual flight pattern - both males and females fly fast and low, with their abdomens curved upwards. You may see individual moths, or they may swarm. Pepper moth caterpillars are photophobic, which means they do not like light. If you shine a flashlight on a pepper moth caterpillar, it will become agitated, moving rapidly side to side.
How the pepper moth got here
Pepper moths have been present in Europe for a very long time. In 1984, it became a greenhouse pest in Europe and Canada for the cut flower, vegetable, and aquatic plant industries. It is believed to have been spread globally through infested plants from those products. [Yet another example of why it is so important to quarantine new plants!] By 1988, the pepper moth had developed a taste for strawberries. In 2004, the pepper moth was found on begonia plants in San Diego, CA. It was again detected in 2010. By 2011, the European pepper moth had been found in seventeen California counties, as well as in fourteen other states. Departments of Agriculture in each of these states is monitoring for this pest. If you think you see one, please try to capture it and report it to your local County Extension Office.
Native to Europe, the pepper moth moth prefers fresh and saltwater marshes. You might think, since you don’t have a marsh in your garden, that your plants are safe. But most of us have a creek, reservoir, or some other body of water nearby, and a pepper moth can fly up to 62 miles.
Also, check the debris (detritus) that falls from container plants and around the base of the containers for signs of eggs or pupae. You can also lightly brush the soil around potentially infested plants for signs of pupae and cocoons.
How to control European pepper moths
At this point, the best biological controls are to spray Bacillus thuringiensis (Bt) or beneficial nematodes (Heterorhabditis bacteriophora and Steinernema spp.). Rove beetles seem to enjoy feeding on pepper moth eggs and caterpillars, and certain predatory mites and wasps also parasitize these pests, so avoid using broad-spectrum pesticides. Since pepper moths prefer moist, hidden areas, keeping your garden tidy and free of overly moist areas can reduce the chance of perpetuating the species in your neck of the woods.
Again, because this is a relatively new pest, with the potential for significant long term damage, if you see one, please report it. If you live in California, you can call 1-800-491-1899. If you live elsewhere, contact your local Department of Agriculture for reporting instructions. Knowing where this pest is can help in its eradication, which is really good news for your tomatoes, basil, figs, and cucumbers!
You can grow a surprising amount of food in your own yard. Ask me how!