These worms may be cankerworms but they may also be the larvae of the winter moth or gypsy moth. All of them can be stopped by spraying with Bacillus thuringiensis (aka Bt) as soon as the foliage emerges in the spring or while the worms are small. Once they get to be a certain size, only the hardcore insecticide sprays like Sevin, Malathion, etc. will take them out. I've had to use them on my japanese maples in the past. Your trees will be OK. They will put on a second set of leaves in another month or so. Just keep them watered well so they have enough energy to refoliate. It takes a lot out of them to put on a second set of leaves. If this defoliation takes place several years in a row, it can severely stress, stunt, or kill a small tree and possibly even a larger one. I would get a handle on the situation next year before the worms can do their damage.

Tree Oracle - thanks - I don't like to use insecticides, so will just keep picking off, and will get the Bt next year.

I have found that bt works on larger worms catapillers etc as well( maybe not mothra types ;>) ) it is safe to use and would recommend using it now unless you enjoy your current picking routine..I have used it on tent cats as well as many other plant eating worms and have found it effective but it's your choice...IMHO it's worth a try... David

Hi,
I just wanted to thank you for your good advice back in 06. Last year I moved in to a new house and noticed the problem all my native maples had. The Norway maples were defoliated by cankerworms. Back in the fall I started landscaping and planted trees. I read this post and made sure I was prepared for 07. Today I finally noticed the baby worms eating holes in my Japanese maple Âbloodgood and my Kwanzan flowering cherry. I sprayed them with BT today and I was wondering how often should I spray them? It doesnÂt say on the bottle. Should I spray them once a week until June?
Thanks,
J

I believe these are fall cankerworms on a water oak tree in my yard. I plan on picking them off by hand and disposing them.
How can I upload a picture of the worms on my oak tree?

I have these in my yard this year eating away at the trees. I read up on them and it appears that ichneumon wasps, or rather their larva, eat these guys for lunch. But how does one get ichneumon wasps? Plant daisies. The adults drink nectar from nice large flat flowers in the families Asteraceae and Apiaceae. ie. shasta daisies, blue fringe daisies, Queen Anne's lace, dill, fleabanes(Erigerons), coreopsis, cosmos etc etc etc . How do the wasps get rid of the worms? The mother wasps deposit their eggs on the worms and when the babies hatch they are on a traveling buffet (the larva eat the worm).
I also recommend asking the appropriate animal spirit to come to you. This may sound silly to some, but it works for me. Ask and you shall receive.

We are infested with cankerworms in parts of NC. Next year I will be "banding" every tree I can but meanwhile they are dropping from my will oak to my little Japanese maple. I may try pesticide bec we still have about 4 more weeks of worms dropping out of trees to forage (I won't even discuss the feces they produce). Has anyone tried some kind of light netting to cover their ornamental maples? Will it hurt them? Help protect? right now most leaves are brilliant and full but I can see the carnage starting. Every year the tree ends up damaged and struggling through the season while I cross my fingers.

My two fringe trees have been completely defolated this spring. Do you think they will be able to survive?

They have completely defoliated my 25 year old japanese maple! We sprayed with Captain Jack's dead bug last night.(spinosad)) Hope it works.