Leafminers are small larval stages of insects that feed on the tissue between the upper and lower surfaces of leaves on many trees and shrubs. As a Tree Service in Central PA, we often see leafminer damage on Hollies, Boxwoods, Birches, and Arborvitae just to name a few. The host plants may show no symptoms of decline for several years, however, repeated leaf loss year after year, could be fatal. These insects damage plant tissues that are essential for performing photosynthesis, the process in which plants create food sources. Leafminer damage also makes its host plant more susceptible to secondary insect and disease issues. Obviously the more stresses a plant has, the more likely it faces an early death.
Their name is derived from the “mining” activity that they cause, tunneling around inside the leaves. Identifying leafminer activity is an easy thing to diagnose once you know what you’re looking for. Leaf mines can vary in their shape and appearance based on the specific leafmining insect. Damage patterns can be serpentine, blotches, tentiform (bulges), or a combination of all of these. The mined areas discolor and dry out at most times and can cause premature leaf drop.
Insect control for trees and shrubs varies based upon the specific insect. Since the larvae are inside the leaf tissue, the best chance of control is achieved by a systemic material that will circulate through the inner parts of the plant, meeting the feeding leafminer. Spray treatments can also help for certain pests as some can be absorbed through the leaf tissues.
Timing of application is important as well, so research your specific leafmining insect and host plant to know when is the best time for these treatments to your trees and shrubs. A tree service with Certified Arborists will know the best course of action for your landscape health and can custom-build a tree and shrub program that will treat for these insects both in a preventive and curative nature.