Ants

Why do ants go up into the trees and shrubs?

Ants go up into the trees and shrubs to collect the honeydew which is secreted by aprids feeding on the tree leaves

Aphids

What type of damage is done by aphids feeding on plants?

The aphid is a small soft bodied insect which sucks sap from the plant. As the aphids feed they secrete a sticky honeydew solution that drips down on to whatever is under them.

What type of plants are infected with aphids?

They really aren't very particular about what type of plant they select to feed on. The honeysuckle bushes, snowball bushes and elm trees always seem to have their share of aphids.

Should aphids be sprayed for?

Guess that's pretty much a personal choice. If the aphids cause the plant leaves to roll or if their honeydew drips onto the deck, sidewalk or car spraying will be needed. Most of the common insecticides will control the aphids.

Why are ants usually active where the aphids are feeding?

The ants collect the honeydew secreted by the aphids and carry it back to their nests.

Ash Flower Galls

What cause the dark colored clusters in ash trees?

Male ash trees have ash flower galls. They are caused by insects feeding on the male flower clusters on the trees in early spring.

Ash Plant Bugs

What cause small white spots to appear on the leaves. In some cases the whole leaf will turn brown and crispy?

This type of damage is caused by the ash plant bugs. They are a sucking insect which draws sap from the plant leaves

Should they be sprayed?

Guess that depends on the amount of damage they are doing and the size of the tree. On a young tree with a limited number of leaves it may be beneficial to spray with malathion or diazinon.

How long will they continue to be a problem?

Even though we only have 2 generations a year in this area it seems as if they are an on and off problem through out much of the growing season.

How do they overwinter?

They overwinter as eggs on small twigs and branches in ash trees. They hatch shortly after the leaves emerge in the spring of the year.

Birch Borers

How do the borers kill birch trees?

The adult borer lays her eggs into the bark of the tree. The larvae hatch out and bore into the area between the bark and wood of the tree. As they feed they work in a spiral pattern eventually girdling the tree.

What can be done to control the borers?

The only time they can be controlled is after the adult emerges in late spring and before she lays her eggs. Usually that occurs during the month of June. During this period of time we recommend 3 applications of Lindane or Dursban at about 3 week intervals starting in mid June.

Why do birch trees do poorly in this area?

The birch is well adapted to areas of partial shade, light acidic soil and good rainfall. Just the opposite of the conditions we have here in the Red River Valley. The adversity of our growing conditions stress the trees, which are then attacked by the birch borer. Birch are considered a relatively short lived tree here.

Cankerworms

What damage is done to plants by cankerworms?

Cankerworms feed on elms, ash, apple and many other plants. People usually don't notice the worms until they reach a fairly large size and are really eating the leaves off the trees.

Can we spray to control cankerworms?

Yes, but spray as soon as you know that you have a problem. The smaller the worms are the easier they are to control and the less damage they will do.

What chemicals can be used?

Several insecticides such as Malathion, Sevin and Methoxychlor will give good control. The bacterial insecticide Bacillus thuringensis sold as Dipel or Biotrol also does a good job and has the added advantage of being non toxic to everything except cankerworms and similar worms.

What can be done for trees, if the cankerworms strip off all their leaves?

Trees which are completely defoliated usually leaf out again within 2-3 weeks after the worms stop feeding. If conditions are dry we suggest additional watering to help the trees releaf.

Why would tanglefoot keep the cankerworms from feeding on the trees?

The female fall cankerworm crawls up into the trees to lay her eggs just after the first frost in the fall. Since she can't fly and must climb the trunk to get up into the tree a barrier of tanglefoot will prevent this from happening.

How is the tanglefoot applied to the tree trunk?

It's best to smooth down the ridges of bark before applying the tanglefoot. The band of tanglefoot should be 4-6 inches wide, 1/16 of an inch thick and 5-6 feet above ground. When smoothing down the bark be careful not to damage the live bark underneath. Apply a continuous band of tanglefoot to the scraped bark using a putty knife or old paint brush.

How often should the tanglefoot be applied?

After the initial application you should add more tanglefoot in the spring just after the ground thaws out and about Labor Day in the fall if the tanglefoot has lost its stickiness.

Forest Tent Caterpillar

Are they similar in appearance to the cankerworms?

They are both caterpillars, but fairly easy to tell apart. The forest tent caterpillars are black in color with distinct dark hair. The more mature larvae have a broad band of blue on each side.

What type of damage is done by the forest tent caterpillars?

They feed on tree leaves just like the cankerworms.

What kind of trees do they prefer?

They prefer green ash, birch, apples, mayday trees as well as many other trees and shrubs.

Do they form a tent or web in the tree?

No, even though they are called a forest tent caterpillar they don't congregate in a tent or web. They cluster together in masses when resting or during unfavorable weather conditions.

What can be used for control?

Same time and spray as cankerworms. Use Dipel, malathion, etc.

Honeysuckle Aphids

What type of damage is done by the aphids?

The aphids are sucking insects which draw sap from the honeysuckle shrubs and cause the new growth to be distorted and stunted.

What can be done to control the aphids?

Since the Honeysuckle aphid is a continuous on going problem with the honeysuckle it takes a very intense spray program to effectively control the aphids.

What type of chemicals will give the best control?

Usually we recommend using Orthene or another systemic insecticide for the best control. Insecticides such as malathion control aphids but will not penetrate the rolled up distorted leaves.

Will the aphids kill the honeysuckle shrubs if not controlled?

It would take an awful lot of aphids on a honeysuckle to kill it, but they sure keep the shrubs looking sick.

Leaf Miners on Birch

What is causing the birch leaves to turn brown?

The browning of the birch leaves is caused by a small worm eating the inner green areas in the leaves. A small fly lays her eggs directly into the leaf. The eggs hatch and the larvae feed on inner leaf tissue.

Can anything be done to control the insect now?

No, once the egg has been laid into the leaf control is difficult. The key to control is to apply a spray such as Lindane to control the sawfly adult before she lays her egg or apply a systemic such a Orthene when the mines are still small. Control can be applied just as the leaves are expanding or when the first mines are observed.

Can the leaf miners damage the tree?

Usually the damage is just cosmetic. The University of Minnesota has found that up to 40% of the tree can be defoliated without being seriously injured.

Maple Leaf Galls

What causes the small red & green bumps on the leaves?

The growths on the leaves are called galls. They are caused by a small mite feeding on the young leaves just as they develop in early spring. Galls will not kill or damage the tree but are just unsightly.

Can anything be done for them now?

No, the insect which caused the problem is long since gone. If it is a severe problem this year, the trees can be sprayed with lime sulphur before they leaf out next spring and twice with Malathion after they start leafing out. This will help reduce the insects and in turn reduce the number of galls. 

Spider Mites

What type of damage do spider mites cause plants?

Spider mites are tiny plant pests which suck sap from plant needles or leaves. They multiply rapidly and can even kill large evergreen trees if not controlled.

Which plants can get infected with mites?

Almost any plant can have mites but some of the most commonly infected plants include: evergreens, potentillas, marigolds, raspberries and many different houseplants.

How can we tell when plants have mites?

Spider mite infestations can be detected by holding a piece of white paper under a suspect branch or leaves. Tap the branch lightly. If mites are present they'll fall onto the paper and appear as tiny crawling specks.

How can they be controlled?

Mites can be controlled by applying an insect such as malathion or kelthane or by physically washing them from the plants with a strong spray of water. Treatment must be repeated weekly for at least 3 weeks.

This page was last updated August 2002

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