Green Worms - Knowledgebase Question

Watertown, Ma
Question by mmckr
February 24, 2011
Hello, last year in early spring I had green worms about a half inch long all over my Katsura Japanese Maple that ate all the new leaves on the tree. I wanted to know what I should use to prevent that from happening this year. Thank you

Answer from NGA
February 24, 2011


Those nasty green worms are the larvae of moths and you're right, they can defoliate a tree in a matter of days. The best approach is to spray your tree with Bt (bacillus thuringensis). Bt is a bacterium that acts as a stomach poison, targeting only caterpillars. The caterpillars have to consume the treated foliage so you'll see some damage, but not nearly as much as if you did not spray. The good news is that the pests are cyclic. Some years you won't see them at all and other years you'll see lots of them. So, spray your tree as soon as you see the pests and you'll take care of them - for this year, at least. Best wishes with your tree!

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