Answer: There is not a good way to control webworms if you can't reach them with a spray. They have natural enemies, such as wasps, which will help keep their numbers down, so try not to destroy these allies in the war. I don't suggest you top the tree as it will disfigure it and only put off the problem for a few years. In the mean time, much production would be lost.
You might try to rent a sprayer or check for a local person who would agree to spray your tree for a small fee. If you do spray, select a product with B.t. This is a natural caterpillar control and is much safer to use. It also won't harm your beneficial organisms.
Thanks for the question!
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