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Solutions to summer landscape and garden problems in central Oklahoma

Insect feeding can cause “Swiss cheese” holes in leaves. [PROVIDED/JULIA LAUGHLIN]
Insect feeding can cause “Swiss cheese” holes in leaves. [PROVIDED/JULIA LAUGHLIN]

We always begin to see different kinds of damage on landscape and garden plants in midsummer. Often the symptoms are only caused by our intense heat and lack of rain and many plants will recover fine.

It can be difficult to determine whether you have a disease or pest problem, or whether a symptom is just environmental stress.

Wilting is an obvious heat and drought symptom on garden plants and younger or smaller trees and shrubs, but heat also often can cause the leaves to “scorch” or “burn” on the edges of tree and shrub leaves. If the damage you are seeing is only marginal and on the very edges of leaves, it is probably just scorch and the plant should survive. Newly planted plants are most susceptible, but established plants also can show this sign of stress.

Another symptom of heat and drought on landscape trees and shrubs is the development of clear yellow leaves, which eventually fall from the plant. Usually, this is nothing to be concerned about unless you see the entire plant defoliating.

Mature landscape trees do not require watering since their deep and extensive root systems can handle the stress. Younger, newly planted garden and landscape plants will need a slow, deep watering once a week in absence of rainfall.

Heat and drought symptoms should not be confused with the various plant diseases we often deal with in the landscape, which can cause dark circular spots on leaves, blackened or powdery white tissue, or various other symptoms.

Some of the plant diseases that we are seeing right now include black spot on roses, powdery mildew on garden flowers and shrubs, and various leaf spot diseases on tomatoes and many ornamental trees and shrubs.

Insect damage on plants appears as holes in the leaves, usually leaving a “Swiss cheese” appearance or chewing damage on the leaf edges. Grasshoppers have been very damaging this summer and will chew on the leaves of almost any plant they encounter!

Insects also can damage plants in other ways like sucking juices from leaves (spider mites) or by forming bags (bagworms) or webs (webworms.) Crape myrtle bark scale is an insect that diminishes the appearance of infested plants by depositing a sugary substance called “honeydew” on the branches and foliage and causes the growth of black sooty mold.

If you think you have a problem on a landscape or garden plant but are unable to identify it, you can visit with your local nursery or garden center employee or we can help you with it here at the Extension Center. Email us pictures of your problem to

The OSU Extension Service also offers many fact sheets to help you identify problems and make safe and effective control measures, like Fact Sheet No. 7306, “Ornamental and Lawn Pest Control,” and No. 7607, “Diseases of Roses,” plus many more, available at .

In order to save money and time while also protecting wildlife, pollinators and the environment, you should never spray for insect or disease control unless you know exactly what your problem is and the correct treatment and timing for controlling it. Often the insect that was feeding already has finished its life cycle and moved on, and the timing is wrong to effectively spray for a disease. If you do choose to use a pesticide product, use the safest method available and always follow label instructions.

Email Julia Laughlin, Oklahoma County Extension Horticulture educator, at .

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<strong>Julia Laughlin</strong>

Julia Laughlin

<figure><img src="//" alt="Photo - Julia Laughlin " title=" Julia Laughlin "><figcaption> Julia Laughlin </figcaption></figure><figure><img src="//" alt="Photo - Insect feeding can cause “Swiss cheese” holes in leaves. [PROVIDED/JULIA LAUGHLIN] " title=" Insect feeding can cause “Swiss cheese” holes in leaves. [PROVIDED/JULIA LAUGHLIN] "><figcaption> Insect feeding can cause “Swiss cheese” holes in leaves. [PROVIDED/JULIA LAUGHLIN] </figcaption></figure>