What is the appropriate time of year to spray for leaf miner and when is it too late to spray. I am in south Etobicoke.
It is difficult to address this question because we don’t know the type of leaf miner you’re trying to manage (or the host plant). Here are some links to Toronto Master Gardener posts about leaf miners. If these don’t capture the type of leaf miner you’re dealing with, please write back with more information and a photo if possible. You can also use the search function (“Find it here”) on the Toronto Master Gardeners homepage to search for your specific leaf miner.
Boxwood leaf miner? – Toronto Master Gardeners
Columbine Leaf Miner – Toronto Master Gardeners
Rose Leaf Miner* – Toronto Master Gardeners
Birch Leafminer: A Toronto Master Gardeners Guide – Toronto Master Gardeners