Thank you for taking my question.
Four years ago we planted two young apple trees in our full-day sun backyard (clay soil) in Barrie Ontario. I think they are being infested by some kind of caterpillar, because usually there are webby stringy bits on the trees. This year, both trees had lots of healthy looking blossoms but they’ve since withered and I see the leaves have been chewed. I have no idea what is chewing them, as I don’t actually see any creatures on the tree. I’m hoping you might be able to tell me what is wrong and how to fix it. I’ve attached a photo below. In case it’s not obvious, I am a less-than-novice gardner !
Unfortunately, fruit trees particularly apple trees are susceptible to a wide variety of insects and diseases.
Some problems are cosmetic while others can destroy the fruit crop or the tree itself. Commercial orchards use an extensive spray program to control insects. It is illegal for homeowners to use these pesticide products in Ontario, so it’s very difficult to control these pests. You don’t say whether or not these insects affect the fruit as well.
Eastern Tent Caterpillars may be the culprit. Their eggs may have hatched and the tiny, black fuzzy larvae can be seen inside webby tents found in tree branch crotches. To destroy the larvae, remove and destroy the tents during daylight hours in the first week or two after their appearance. Since the young larvae come out of their tents to feed at night, apply the biological insecticide B.t on the foliage during the evening. Larvae will turn black and die approximately 3-5 days after eating the B.t. residue on the foliage.
It could be that Gypsy Moth eggs are hatching, too. B.t. can be helpful to control their larvae also. You can install a burlap skirt at the base of the tree to create a shady, protected area for larvae to hide during the day. Every day, inspect the burlap skirts and underlying bark crevices in early afternoon and remove/destroy larvae. Sticky bands around trunks during the June/July flight period will help prevent females from laying eggs above the bands and will attract males to the sticky surface.
The following two articles were previously posted on the Toronto Master Gardener Website: