Master Gardener Sue Morris: University of Minnesota says avoid tree pruning amid drought

Drought-stressed trees should not be pruned. Soapy water works to destroy some insect pests if used properly.


Are you seeing drought-stressed trees in your yard or when driving around? I think we will be seeing the results of this drought in our trees for several years to come.

Some signs may not always show up right away. Most trees are experiencing some level of stress. How can you tell? Signs to look for are leaf wilting, curling, discoloration and early leaf drop. Some trees may produce abundant seeds.

Pruning is usually good for trees because it promotes their health and improves the size and form of the tree. However, the University of Minnesota is warning the public that stressed trees are more susceptible to disease and insects and pruning can increase that risk further so it’s a good idea to limit or avoid pruning this year.

Branches that are infected, dead or broken should be removed right away to avoid injury to the tree. It’s usually better to prune trees during the late winter or early spring when insect and disease activity is low.

Remember oak trees should not be pruned during spring and summer to avoid spreading oak wilt. I recently heard that you shouldn’t even prune dead branches off oaks during that time period.


Soapy water

Have you heard that a way to safely destroy insect pests in the garden is to drench with soapy water? It has been said that it will not harm beneficial insects.

Recently the University of Minnesota’s Yard and Garden sent out some tips on the proper way to use soapy water. It has been said that the soap washes off a protective coating on the insect’s body causing it to dry out.

Dish soap and water are often referred to as the holy grail for managing insects from aphids to beetles. Understanding how soap impacts insects and how to best use soaps means better insect management and healthier plants.

Insects susceptible to this method are small, soft-bodied insects (i.e., aphids, whiteflies, thrips and mites).

It is also occasionally effective on larger insects such as boxelder bugs. This means that soap is safe for pollinators and natural enemies. As long as you aren’t coating them in the soap, they won’t be bothered. Caterpillars and beetles are unlikely to be affected.

The soapy water needs to touch and coat the insect’s body in order to work.

You will need to turn over the leaves to reach those on the underside of leaves. The spray could also knock the insects off the plant if you use high-pressure spray.

In order for this to work, you must see the insects because residue soap won’t bother them if they eat it. You must have contact with the bug.


The University recommends we shop for the soap at the store instead of our pantry. You can buy ready-to-use insecticidal soap.

If you make your own, be careful so you don’t burn the plant you are trying to save. A 2 percent soap solution is right — 2 teaspoons of dish soap to a pint of water. High concentrations of soap in hot and humid weather when a plant is stressed is not a good thing.

Caution: Tomatoes are sensitive to soapy water.

Here is a word of caution from the University of Minnesota. Always follow the pesticide label directions attached to the pesticide container you are using. Remember, the label is the law. It is important to read the small print on those labels.

Related Topics: HOME AND GARDEN
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