Archived Story

Serious tree problems usually involve bugs

Published 5:59am Monday, January 20, 2014

As we were saying… there are many conditions about trees that look bad but are totally harmless, and a few that you need to be concerned about.

You are out walking among your pine trees and see what looks like someone spit on a few of the twigs. Spittle bugs can be found on most any growing plant including trees.

You can dislodge them with a strong blast from the hose, a squirt of insecticidal soap or, on trees, horticultural oil.

You notice a line of big, black ants charging up the trunk of your tree.

You have carpenter ants feeding on dead wood. This can be very bad and it is a good idea to have an expert examine the tree; it can have a structural weakness.

The next wind storm can bring it down on your new Cadillac.

Our ash trees have enough problems with the Emerald Ash borer; however, they are also prey to ash flower gall. This eriophyd mite attacks the flowers of the tree causing them to become distorted and black.

Ugly but, unless you just can’t stand to look at them, treatment is not recommended.

Oak trees growing on sandy soil are at risk of death from the 2 lined Chestnut borer.

They prefer mature oaks growing on slopes.

They will attack all oaks but prefer red oaks. Adults emerge about mid-June, staying close to an already infected tree.

They lay eggs in the bark cracks on the trunk and larger branches, usually in sunny spots.

The eggs hatch in about 10 to 14 days and the thin, white larvae begin feeding on the cambium, the growing part of the tree.

This destroys the trees’ ability to move water and nutrients.

Late summer, the larvae complete their development and move back into the outer bark and build hibernation chambers to winter in.

They emerge in the spring as adults. It may take as long as 2 years to complete this cycle.

Symptoms of this borers’ attack usually show up in late summer when leaves of the infested tree wilt and turn brown but don’t fall off.

Treatment is not usually effective.

About all you can do is keep your oaks well watered and fed and be careful not to damage the roots, or changing the soil grade or drainage.

Another troublemaker is the pine bark beetle.  This beetle usually attacks drought stressed pines.

They like red, jack, Scots, Mungho and Austrian pine, but can come after white pines and spruces.

The beetle over winters in the duff layer of needles under the tree.

The tiny, ¼ inch long red-brown or black females lay eggs in the spring. The resulting larvae burrow into the bark of stressed trees, or freshly cut logs.

As in other tree damaging beetles and borers, they disrupt the water and nutrient uptake as they damage the cambium.

The tree will turn brown and die.  A sign of their attack is the pin head sized holes they leave in the bark as the adults emerge.

Control them by doing your thinning or pruning in the late fall or winter and removing any damaged branches and logs and burning them.

Keep the trees well watered and fed, as chemicals aren’t a practical control for the beetle.

We love our trees and don’t want them damaged. Now you know what to panic about and what to ignore.

 

Bev Johnson is an Extension Master Gardener in Otter Tail County.

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