Q: I recently noticed in the crook of a few of my trees white webs with lots of tiny worms squirming inside. Do you have any idea what this is and what to do about it?
A: You undoubtedly have tent caterpillars. Each one is basically a “stomach with legs”. Their existence is dominated by the urge to eat as many leaves as possible in the shortest time period. Cherry limbs (and entire trees!) can be completely defoliated in a few days – but the damage is not permanent. The caterpillars will soon drop from the tree and change into pupae in the ground. In a month or so, small moths will hatch under the tree. At the end of the summer, they will lay a mass of eggs on small twigs in nearby cherry trees. The eggs will hatch and start the cycle over again next year!
No control measures are really necessary unless the webs mar your landscape or the caterpillars are dropping onto a deck or patio. Destroying the “tent” with a long stick exposes the critters to birds, weather and other predators. Spray an organic pesticide containing Bacillus thuringiensis, which will kill many worms and stop their feeding. Some commonly available products are Thuricide, Dipel, and Caterpillar Attack.