I notice on a lower branch the leaves had holes. I applied dormant oil early April, but the spout of the sprayer did not have the nipple device to enable an even spray. It only sprayed in 2 directions. It was difficult to spray the tree well. The tree is a mature tree. It needed more pruning, but I did what I could to not shock the tree. I can not send a picture as they say the file is too big
Thank you for contacting the Toronto Master Gardeners.
There are a number of insects that could be eating the leaves of your tree. Caterpillars, sawflies, leafminers, beetles, worms and other insect larvae attack various species of trees consuming their leaves. Hand picking leaf-eating pests such as caterpillars will help control these pests, however this isn’t fesible if your tree is very tall.
You might consider applying Bacillus thuringiensis specifically targets leaf-eating caterpillars without harming beneficial insects, wildlife, humans or pets. Bacillus thuringiensis is a microbe that is naturally found in the soil. This microbe forms proteins that are toxic to certain larvae. There are many types of Bt. Each targets different insect groups.
Keeping your tree healthy is your first line of defense. The yearly addition of organic compost along with a layer of mulch ( making sure to keep the mulch away from the tree trunk) and regular watering will keep your tree happy and healthy.
The Toronto master Gardeners along with the City of Toronto have put together a number of fact sheet on organic gardening which you might find of use.
Controlling Insects Without Pesticides: A Toronto Master Gardeners Guide
Improving Your Soil Organically: A Toronto Master Gardeners Guide
How to Control Plant Diseases without Pesticides: A Toronto Master Gardeners Guide
Organic Fertilizers: The Basics: A Toronto Master Gardeners Guide
You may also be interested in the following articles on Horticultural oil and Continuing to protect apple trees from apple scab and fire blight.
Lastely OMAFRA has an online gardeners’ handbook on fruit apple, crabapple, pear
References:
https://homeguides.sfgate.com/spray-leaf-eaters-trees-46530.html