White worm/caterpillar infestation on tree leaves

Asked July 16, 2017, 9:03 PM EDT

Hello, All of a sudden, I have tree leaves being destroyed and I'm noticing some leaves are fully coated with white worm/caterpillars. I am hoping you can help me figure out what this is and how to get rid of these specimens. I'm afraid I will loose this tree. I am also not sure what type of tree this is? (Chestnut oak) ? Thank you, Melanie zevan

Lackawanna County Pennsylvania

8 Responses

I sent your question to Penn State entomology. I'll email you when I get an answer. Meanwhile, if you can, cut off the infested leaves you can reach and drop them in a bucket of soapy water.

Here is the answer from Penn State Entomology:

Those are hickory tussock moth caterpillars (Lophocampa caryae). They feed on a wide variety of hardwoods, including ash, oak, hickory, maple, elm, and walnut, as well as some shrubs and vines. The adults fly in May and June and caterpillars are present July through September. They can be gregarious when young (as in the photo), but will become solitary as they mature. The hairs cause irritation, so caution should be used if handling them.

If left untreated, the caterpillars will likely cause some defoliation of the tree, but unless the tree experiences defoliation multiple years in a row, it should recover with no lasting effects next year. Personally, I wouldn't treat the caterpillars unless the tree is stressed due to other factors and they are likely to push it over the edge (and if that's the case, those other stressors should be addressed as well).

If treatment is warrented, there are a number of products and active ingredients registered for treatment of caterpillars on landscape trees that are available at most garden shops/plant nurseries and big box stores (e.g. Walmart, Home Depot, &c.). A product that uses BT as the active ingredient would be very safe for the tree, humans, and beneficial insects as BT specifically targets moth caterpillars. Any insecticide that is used should be used according to the label rates and instructions.

thank you for a quick response. I appreciate it! This tree is stressed. As I continue to watch it.... many of the branches are sparse and towards the top where I can't reach it. I might have to use the products you recommended.

thank you,

Just be careful and follow the label directions. Pesticides are tricky. You don't want to breath them in or have the spray land on you. You can find the warning labels online for each product, and if you feel uneasy, I recommend you hire a landscaper to spray your tree.

Hello again and thank you for your help.
this afternoon, all of a sudden, I have sawfly caterpillars on my mugo pines. I dealt with this 4 years ago. I put soapy water over all of the mugs pines.
However, is there a way to prevent these caterpillars from ever arriving? Or do they prefer a lot of rain and humidity? (Like it's been this summer). Any advice is appreciated. I, obviously have lots of caterpillar issues.

Sadly you can't stop nature. There is a product called BT on the market that is a biological control for caterpillars. It's a commonly occurring soil bacteria and is available at garden centers. However insecticidal soap works just as well. Caterpillars are only around for a couple of weeks,
I don't know how big your mugo pines are, but I usually use a net cover during the time a certain pest is laying eggs. You can make one from a sheer curtain from Walmart. You have to make sure it covers the whole plant and is covered with boards at the bottom or tucked into the soil. Blueberry farmers use insect net on their bushes for similar reasons. You can search insect net online if a sheer curtain is too small. Also, check out the life cycle of the pest of the moment so you know when the moths are mating and laying eggs. Exclusion is always the best way to control any pest. They get acclimated to pesticides and fungicides, but not exclusion.

i had a difficult time finding a product that had bt in it. My local garden store and ace store told me they never heard of it. They told me that they carry 70 percent neem oil by Monterey. They to,d me that penn state recommends this product for caterpillars. So, is this good for me to use?
thank you for your help and time. Melanie

Neem oil, insecticidal soap, horticultural oil, all these products work by suffocating the pest. They will work on caterpillars as long as you thoroughly cover every branch and leaf top and underside. The product Penn State is recommending is BT which stands for Bacillus thermogenesis. a soil bacteria that is lethal to caterpillars when they ingest it. BT is used to control gypsy moths, a similar kind of pest. Bonide is a name brand that makes BT concentrate and sells it on Amazon. I have also seen it in Walmart from a different vendor.
Whatever you use, the spray has to reach every part of the tree, It takes a powerful spraying device to cover the canopy of a full grown tree. All the untreated branches will still be food for the caterpillars. I recommend you call landscaping companies that have a pesticide license and get several bids so you know what that will cost. Then you can weigh your options.