Published on 06/19/03

Scout your landscape for disease, insect problems

By Bob Westerfield
University of Georgia

The muggy heat makes working in the landscape less appealing than it was in the spring. But insect, disease and other plant problems need attending to.

To keep your landscape looking its best, be a Sherlock Holmes in your yard. Frequent visits to keep an eye on things is often all you need to detect problems before they get too big.

A trowel, a white index card and perhaps a hand pruner will help you with your landscape detective work.

First, visit your annuals or herbaceous perennials. These plants usually need the most immediate attention. Are they healthy, green and strong or spindly, yellow and weak? Perhaps they need a little fertilizer. Annuals, in particular, benefit from light, frequent applications.

Look closely

Be careful, though. Look closely. Yellowing of these plants can also mean too much water, and recent rains have kept the soil fairly wet.

Dig down a little to see how wet the soil is and how well it's draining. Heavy, wet soils can play havoc on many landscape plants and may be hard to remedy without renovating the bed.

Look at the blooms of these plants. Deadheading, or removing spent flowers, will help keep them blooming all summer. Check the blooms, too, for signs of insects or disease.

Look carefully at the foliage on all plants. Are the leaves spotted or riddled with holes? Are they speckled, bronze-colored or different from the way you remembered?

Leaf spots

Leaf spots can be caused by insects or disease. Usually, if it's disease, a yellow or purple halo will be around the dark spot. You may need to use a fungicide. Sometimes, improving the air circulation by lightly pruning will improve a plant's health, too.

Insect damage may appear as solid, blackish-brown spots, chewed areas or speckled leaves. Be sure to look at the undersides of the leaves. Many insects will feed and hide there.

Properly identifying the insect is the key in selecting the correct control. Remember, there are far more beneficial insects out there than bad guys. Beneficials do an outstanding job of keeping damaging insects at bay on their own.

Buy a good insect-ID book and learn how to tell the good bugs from the bad. Treat plants only when pests are causing more damage than you can live with.

Hard to see

Some insects are so tiny they're hard to see. This is where your white index card can help. If you see speckled or off-colored foliage and suspect insects but can't see any, shake the leaves briskly over the index card. You may see tiny red specks called spider mites.

Spider mites can build up heavy infestations quickly if conditions are right. To control these pests, use a product labeled for mite control.

Check azaleas for off-colored foliage, too. A common summer problem is lace bugs, which feed on the undersides of the leaves of azaleas, cotoneasters and other plants. They have many generations of offspring, so keep a watch and control this one all summer.

Chewing damage

Chewing damage on leaves often indicates another type of insect damage. This can be caused by many insects, including Japanese beetles, leaf beetles, snails and slugs.

Once you know which culprit is munching on your plants, select the appropriate control. Insects are usually easier to kill when they're young than when they're mature.

The University of Georgia Extension Service office in your county can help you figure out what caused your landscape problem and the best control measure.

County agents have special diagnostic tools and resources to help them solve almost any landscape problem. Be sure to describe the damage accurately.

Better yet, bring in a fresh sample. While you're at the county agent's office, pick up a few of their many brochures on insect and disease control in the landscape.

(Bob Westerfield is an extension consumer horticulturist with the University of Georgia College of Agricultural and Environmental Sciences.)

Bob Westerfield is a University of Georgia Cooperative Extension consumer horticulturist with the College of Agricultural and Environmental Sciences.