When you see a handsome parachute-shaped tree with millions of fern-like leaves, chances are you are looking at a mimosa, Albizia julibrissin.
It is one of the most beautiful flowering trees you will find. In midsummer, it is covered with fragrant pink-tipped silken tassels.
The tree is fast-growing, hardy, and does well even in poor soil. No wonder it is so widely planted as far north as Boston and all over the South, except in the aridest regions.
The graceful, airy shade of the mimosas, their fragrant flowers, and how they attract hummingbirds make even the necessary spraying against webworms worthwhile.
The Arrival of Troublesome Pest
About three years ago, the mimosa webworm began to appear here in Dandridge, Tennessee. We noticed a few dead leaves on our trees and found what looked like spider webs holding clusters of dead leaves together.
When we pulled the webs apart, we found they contained hundreds of tiny, slender worms.
More worms began to appear on our trees—generally on the newest and tenderest leaves—and we feared they would cover the whole tree in time.
I consulted a Department of Agriculture bulletin. It said that the worms rarely killed trees, but they did permanently disfigure them. Since then, I have seen several trees destroyed by the worms.
Effective Methods of Control
Our county agent advised me to mix 3 tablespoonfuls of a 50 percent DDT wettable powder with each gallon of water and spray the trees thoroughly with this.
There are other insecticides to use, like arsenate of lead and malathion, but DDT was his first choice.
Our trees are large, so we used an elongated sprayer with a drum and pump. You can sometimes borrow these from the county agent’s office or rent them from a local garden supply center.
If you have only two or three medium-sized trees, you can use a hand sprayer and reach the high branches by standing on a step ladder.
Call a professional tree surgeon if you can’t do the work yourself. It’s worth his fee to keep your trees free of this pest.
We learned that the best times to spray are when the leaves are just beginning to come out, when they reach a full leaf, and after the flowers are gone.
We pay particular attention to new growth after trimming the tree. We once noticed webs in winter when the bark had split due to rapid growth, and we sprayed the trees again.
It looks as if we have met the enemy, and he is ours—our trees are healthy and green, and although we occasionally find a webby clump of leaves, the worms are dead.
Limited Impact on Other Plants
One consolation is that the webworms do not seem to touch anything else in the yard.
I have picked off several webbed mimosa leaves from the nandinas, boxwoods, ilex, and mahonias, but none of these plants has ever shown any ill effects from them.
44659 by Jean Bible