I have a young jackmontiei silver birch Half the leaves have been eaten by the sawfly caterpillars before I blasted them off with water. I want ensure that next year I stop them before they eat the leaves. What is the best time to spray the tree with specific incecticide ?
Saw Fly Eradication
Certified GKH Gardening Expert
If you can obtain a product called Bayer Tree and Shrub Granules there, I would highly recommend giving the tree a treatment of the granules in early spring when the tree is first starting to leave out. The systemic insecticide in the granules should take care of the problem. You could follow that up with spraying the foliage down with some Bayer Advanced Complete Insecticide or insecticide of your choice about four weeks later.