A cherry tree assault

unwanted windows in my cherry tree leaf

Something has been eating the leaves of my sour cherry tree (picture below). The tree is still in a pot, scheduled to be planted in a deer-proof fortification this fall. It has been happily growing since I bought it a few months ago. The damage is unsightly, but hopefully not detrimental to the tree. It looks like windows have been installed haphazardly through the leaves exposing the fractal-like veins of each leaf – very reminiscent of the leaf miner damage that has destroyed this summer's chard. The difference is I caught the cherry assaulters red-handed. They look to me like little translucent caterpillars with the colouring of a fresh bird dropping. I took mug shots and sent them to be identified by a master gardener and an entomologist.

The gardener identified them as Western Tentiform Leafminers (Phyllonorycter elmaella), a leafminer big enough to see that prefers apple and cherry trees. They have a distinctive adult form with orange and white stripes – I haven't noticed these, however I have not been looking.

The entomologist identified them as Pear Slugs (Caliroa cerasi), which is not actually a slug but a sawfly. This one also likes munching on fruit trees – including sour cherries like mine. The adult form of these look like a flying ant and I'd have to look really close to tell the difference. Since I assume all flying ants are coming to eat my house, I flatten them on sight.

To me the larvae forms of both the Western Tentiform Leafminers and Pear Slugs look exactly the same! When I noticed these caterpillars on the cherry tree, I picked them all off and squished them, so I can't hold onto one and see what it turns into. Any idea what these pests might be?

pest mug shots