Bugs and disease…….the big picture
I often get calls about young lawn trees with spots or holes on the leaves. I never get calls about the same thing happening in the woods………But I get it. When someone pays good money for a tree and takes care of it they get excited when holes show up in the leaves. Well, it’s usually not a very big deal. When you see the holes and no bug, he’s probably done the damage and moved on. Leaves are not the most critical part of the tree. They come and go every year. Healthy trees might even push out new leaves if they lose their leaves in the spring or early summer. Cosmetic leaf damage is normally a seasonal or occasional problem that the tree can easily overcome. However, repeated defoliation can be a problem as the tree is not producing food, but that’s a rare situation.
You can spray insecticide when you see bug damage but, as mentioned, chances are the bug is already gone. There are “systemic” insecticides that get inside the tree so these products won’t wash off with the rain and they’ll make the tree poisonous to bugs that come along. (This is typical of the pesticide used to control the emerald ash borer) Of course you don’t want to use a systemic insecticide on fruit trees or you’ll be eating poisonous apples! You also want to be sure the problem is a “bug”. “Mites” can be a problem on ornamentals but mites are not “insects” so they’ll require a special miticide. If the problem is a disease you’ll need a “fungicide” which might require repeat applications weekly as fungicides don’t persist very long and wash off in the rain. Fungal disease is typically more of a problem in the spring when it’s cool and wet. (ie. Apple scab on crabapples)
So is this all sounding a bit complicated? It can be……. so I wouldn’t get too concerned about the spots and holes in leaves. Better yet, choose plants that are resistant to common problems! Boring insects, on the other hand, will damage the trunk and this can kill a tree. There are also diseases that get into the trunk and branches that can kill a tree. Some of these can’t be controlled but other measures can be taken. Call me and we’ll deal with those cases individually.
One of the pest problems that has been common the last few years is bagworms. This is a bug that feeds on foliage, usually of evergreens, and can kill them if left uncontrolled for years. Unfortunately the evidence is normally just the overwintering structures that house the bug so many people think it’s a natural structure or even “pine cones”. Sprays need to be timed with emergence of the bug as spraying the “bag” won’t help. Systemic sprays are also helpful here. I’ll include a couple pictures here to illustrate the damage done by bagworms which often results in plant death.
This year has also produced a bumper crop of Japanese beetles. Japanese beetles can be worse in some years than others. They always prefer an acid soil so are typically worse in eastern Ohio. They also start as grubworms in the lawn so treatment of soil grubs can reduce the population of Japanese beetles. They like certain trees and shrubs better than others and simply skeletonize the leaves so it’s a temporary problem. But they can be abundant so I understand the concern. You can purchase a “trap” which is a bag that attracts the bug who enters the “one way hotel”. But it has been said that these traps just attract more bugs to your yard. Yes it will, but most of them end up in the bag so the population is reduced.
All this being said, I see more damage to ornamentals from deer, rabbits, dogs and lawnmowers! Yes, lawnmowers can kill trees! Nature is interesting and wonderful . Don’t stress about it. Enjoy it!