The leaves on my apple tree are skeletonized and covered with lots of webs and white cocoons. What 's causing this?
These are all the hallmarks of the apple ermine moth which makes its home throughout the interior of B.C. and this year is making its home in your apple tree.
The first sign of trouble comes in early spring when the larvae start burrowing through the inside of the leaves, causing that distinctive skeleton effect. As the season progresses, they make their way out of the leaves and start spinning webs as they build themselves the cocoons they'll reside in while they transform into moths. Those moths then lay the eggs that will overwinter in your garden so that the larvae can pop out again next year and cause problems all over again.
Often you can keep ermine moth populations under control by diligently hand-harvesting affected leaves as soon as you see them. Obviously this is easier to do with smaller trees.
If you lose control and the insects start to take over your tree, you may need to take decisive action. Several biological controls are registered to subdue ermine moths and their larvae, so head down to your local garden centre and pick up the one that’s best for you.
You’ll also save yourself a lot of headaches from these and other pests by developing good maintenance practices. Although we like to think that all leaves make good compost, any leaves that come off trees with insect or disease problems should not be composted. They need to either be gathered into a pile and burned, or placed in garbage bags and removed from your property.
Whatever you do, never, ever leave infested leaves on the ground over winter. That’s just playing with fate.
If you have any questions or comments, please send them to me at vanessa@gardenmuse.ca.
Posted on September 2, 2011.
