Tuesday, November 3, 2015

Euonymus Leaf Notcher Moths

A male Euonymus Leaf Notcher Moth (Pryeria sinica), an exotic wasp mimic

     On October 29, 2015, one of our Arlington Regional Master Naturalists, Alison Sheahan, posted a photo and description of numerous moths that appeared in her yard on the master naturalist Google Group. This led to some of speculation as to what these were, since they looked fairly unusual with their clear wings and it was a strange time of year for moths to come out, especially in such large numbers (30-50 of them). They did not fit the description any of the moths I was aware of and so I decided to investigate a bit more.
     It then occurred to me that they might be an exotic species of moth I had read about in an invasive species alert a couple of years before. I asked if I could take a closer look at them and confirm my suspicions. A few days later I visited and was quite sure of what they were, but took some photos and collected some voucher specimens to send to some professional entomologists for confirmation. I then proceeded to ask our Extension Agent for assistance in getting in touch with their entomologist contact and to see what protocols needed to be followed in case they were the invasive pest in the original alert. The visit to our Extension Office provided a nice teachable moment since a Master Gardener class was taking place. This led to an opportunity to talk about invasive species, EDRR (Early Detection, Rapid Response), and how observant citizen scientists can help in detecting potential issues such as these moths could be. The entomologist eventually confirmed my suspicions.

Euonymus Leaf Notchers mating. The males have feathery antennae.

     Euonymus Leaf Notcher Moths were first discovered in North America in 2002 in a Fairfax, Virginia yard where they were causing great damage. The caterpillars were feeding in large numbers. and defoliating the Euonymus shrubs. It took a while before entomologists were able to figure out the exact species, an exotic moth Pryeria sinica. These sporadically showed up in several places in suburban Maryland over the next couple of years, leading Maryland to describe them as invasive species of concern.
     They can apparently survive our winters (they're originally Asian in origin), feed and reproduce in large numbers, are not eaten by many predators, and prefer to feed on various Euonymus species of shrubs, a group of plants used extensively in the landscape industry. They could therefore possibly cause great economic damage. Since we have native Euonymus (Strawberry Bush) and since they can also feed on the very widespread Bittersweet on occasion, their invasive potential is great. They seem to prefer Japanese Euonymus (Japanese Spindle-tree Euonymus japonica), which is what we found them on, but they appeared to also be on the Burning Bush Euonymus shrubs there as well.

Female Euonymus Leaf Notcher laying eggs and an egg mass with protective hairs (modified scales) from their own bodies

     There were several dozen flying that day (November 3) in the warm weather, mating and laying eggs. These moths appear to be wasp mimics, perhaps getting a measure of protection by looking like these stinging insects with their clear, scale-less wings. Euonymus plants have acyanogenic compounds in their leaves protecting them from getting eaten. I think the moths sequester these from when they fed on them as caterpillars and so are somewhat toxic as well. Their body "hairs" (modified scales called setae) likely are defensive as well. When they lay their eggs, they place hairs from their bodies on top to help protect them (see photo). Several moth species that have urticating, protective hairs also cover their eggs and cocoons with them.
     These are daytime flying moths, who come out in great numbers when few other moths or their predators are active. Since they have reduced mouth parts, I'm guessing they don't even feed as adults (it's the caterpillars who feed gregariously and notch the leaves giving them their names).
     Euonymus Leaf Notchers mate near or on their host plants. The females I think send out pheromones which attract the males and other females in large numbers. That is likely why the males have such feathery antennae, to detect the pheromones, and why they were so many together in one location. The females then lay egg masses (about 150 eggs at a time) near the top of pencil-thin Euonymus twigs where they will remain overwinter, hatching in late March or early April.

First instar caterpillars (newly hatched and not molted their first time yet) hang out communally, usually on the underside of the leaf.

     The caterpillars feed communally at first, leaving tell tale notch marks, or completely stripping the plant when in large numbers. They hide under the leaf and can wander far in search of food (as I discovered when a couple got underneath the screen I had them and wandered down the hall).

Multiple instars (molts) of caterpillars.

     Here's a short video of them:

     Some literature suggests just crushing the eggs or snipping the infected twigs off. That's what we did, but returned in the spring to see what we missed. There were hundreds, with us coming back a couple of times to try and eradicate them as their leaf damage gave them away. I'm raising a few to get photos of their complete life cycle, but well over a hundred have been killed, hoping we can contain or eliminate this threat before they spread.
     While their numbers were still low and since they are not strong fliers, it was a good time to get them, before they got established. But we missed some obviously and will have to keep our efforts up. That is one of the reasons for Early Detection and Rapid Response as a way to deal with new invasives. We may be able to prevent them from getting a good foothold, especially if we get the neighborhood and our local folks to keep an eye out for them. I've since heard that they've also just been discovered in Great Britain. Maybe someone will read this and be able to recognize this invasive moth if it moves into their community regardless of where they live.
     All this began when an informed master naturalist was curious about something new that she had never noticed in her yard before and asked her colleagues to help identify them. It just goes to show that keeping an eye out and taking interest in what is around you might lead to hopefully some timely actions.

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