As late summer approaches, ominous webs have begun to pop up across neighborhood trees. These silken nests are the homes of the fall webworm! Fall webworms (Hyphantria cunea) are a species of moth that spend their larval stages in webs within plant material. If you haven’t heard of them, now is a good time to learn, because as autumn approaches they will be more prevalent.
Fall webworms are fuzzy caterpillars that cluster together and weave thick webs on the tips of plant branches. From birth until their final metamorphosis, fall webworms spend their lives in their web community. Within the web, they are protected from natural predators, can eat leaves safely, and can regulate the nest temperature to an ideal 100+ degrees Fahrenheit!
Few trees are off limits to these hungry caterpillars. In fact, there are over 100 tree species that can host the fall webworm. The trees in our area most affected are:
- Pecan trees
- Hickory trees
- Walnut trees
- Oak trees
- Ash trees
- Fruit trees (apple, cherry)
How to Identify
Aside from its namesake webbing on the tips of your foliage, there are several ways to identify the fall webworm. If you are brave enough to approach the spooky webs, you can examine the pests up close to determine if they are in fact fall webworms.
In its caterpillar stage, the fall webworm has several appearances. In their first few stages of life, the caterpillars are usually a translucent yellow-green color.
After a few molts, they have two main appearances – pictured to the left. There are the off-white caterpillars that can have black or yellow spots along their back or black caterpillars with orange-red spots along their back.
Both sub-species can have either black or red heads! Perhaps the most distinguishing feature are the long hairs protruding off their bodies in every larval stage.
Once they undergo metamorphosis, the fall webworm emerges as an elegant snowy-white moth. The wings of an adult moth can be completely white or speckled with brown spots. Generally speaking, the all-white variations appear most often in northern states, and the spotted variation appears in southern states. These moths are nocturnal and don’t utilize the webs anymore, so they are hardly a nuisance compared to their younger selves.
Pest That Are Similar To Fall Webworms
Before you decide to take any action, it is important to identify a pest correctly! There are a few other bugs with similar characteristics to the fall webworm that you should look out for.
Eastern Tent Caterpillar: yes, there is more than one caterpillar spinning webs in trees. The eastern tent caterpillar builds its webs deeper into trees, close to the trunk or in the nooks of branches. The caterpillars are black with yellow and white details; once they emerge as moths they are completely brown, rather different from the fall webworm. Luckily, the season for eastern tent caterpillars has just passed – they are active from April to June. As their season ends, fall webworm season begins!
Spider Mites: these tiny arachnids are almost impossible to spot, but their thin wispy webs are more recognizable. Due to their small size, spider mite webs won’t engulf your tree, a few leaves will suffice for them!
Ways to Treat
As frightening as their nests may seem, fall webworms are not a major threat to healthy trees. This means that most homeowners do not need to apply any treatments! While fall webworms do like to snack on leaves, trees often have enough energy stored up for fall and the caterpillars have little impact on them. Additionally, any leaves that the webworms defoliate would just fall off as autumn arrives a few weeks later.
On the other hand, if you have smaller ornamental plants, fall webworms may pose more of a threat. While we do offer treatment for serious infestations, this treatment is rarely warranted. Instead, we recommend these other non-pesticide approaches to safely remove the webs if you need to.
- Hose down the web! All you need is a regular ole garden hose to knock the webs out of trees! This won’t kill the caterpillars that were in the web, but it does allow birds to take them out for you – and gets the web out of your tree.
- Poke holes into the web to allow natural predators in! Birds, wasps, and other predatory insects have trouble penetrating the thick webs, so using a stick to poke openings into the web allows them to eat the caterpillars.
- Use a stick to take the web down! If you have a long enough stick, you can wind the web up and directly take the caterpillars out of the tree. Check out this video to see how.
Whichever method you choose to go with, please do not utilize any fire or flame devices to aid in removal. This procedure is far more detrimental than it is beneficial – you can put yourself and your yard at risk.
Remember – fall webworms are a fairly neutral bug, and control isn’t required. If you spot their webs this season, the best thing you can do is to keep your trees healthy to survive the upcoming fall! Give your trees a health boost with a fall bio-stimulant!
Are your trees healthy enough to
withstand the fall webworms?
Get a Fall Bio-Stimulant today!