Zoysia Grass Insect and Pest Problems

A thick zoysia grass lawn is the perfect home for a variety of insects and pests. Some feed on grass blades, some feed on grass roots, and some happily feed on each other. In most cases, zoysia grass grows faster than the average insect population can eat and we don't have to worry. In fact, a certain level of insect feeding can actually stimulate growth. Problems arise, however, when insect pests increase in populations large enough to damage the zoysia grass. Luckily, lawn insects can be treated fairly easily with a soil insecticide or with natural products like BT (bacillus thuringiensis) and Milky Spore. The best time for a once a year insect treatment is in late July or early August.

Insect damage is often defined as an irregularly shaped patch of discolored or brown grass in a lawn. If you take a drive around town, you will pass many lawns that could fit that definition. The problem is that only about 1 percent of those lawns have an insect problem. Lawns are finicky and irregular patches of brown grass pop up for different reason. One of the most common is drought. You might think your lawn is evenly watered but even a slight rise or a different soil texture can alter the amount of water that penetrates the soil. When you think you have an insect problem, look for another cause first. Then, wait to see if the troubled lawn area expands. Only then should you worry about treating with a soil insecticide. Following is a list of insects that might cause problems in a zoysia grass lawn. You may never see any of these bugs.

WHITE GRUBS: The most common and problematic insects on zoysia grass lawns in the South are white grubs. White grubs are the larval, soil inhabiting form of several different beetles. The most notorious beetle in the South is the Japanese Beetle, known for its voracious feeding on Crape Myrtle, grapes, ornamental cherry trees, and almost anything green. Japanese Beetles lay their eggs in lawns and grassy areas beginning in July. The eggs hatch as white grubs in late July and begin a two month feeding frenzy on grass roots. As soil temperatures cool in October, the white grubs tunnel down 4 to 8 inches into the soil where they pass the winter. As the soil warms in the spring white grubs move to the surface, feed briefly in April/May, and then pupate. White grubs can be controlled with a granular soil insecticide applied in early August according to the label directions. Milky Spore is a natural product that contains Bacillus popilliae, a disease that kills white grubs. Milky spore will not kill every white grub, but spores will remain active in your lawn for many years.

BILLBUGS: billbugs are black, hard shelled beetles with a curved snout like a short elephant trunk. You may see them moving around in the spring as they prepare to lay their eggs. The eggs hatch into legless white grubs to feed on zoysia grass roots during the late spring and summer. Damage usually appears as circular areas of brown or yellowing grass. Billbugs can be controlled with a soil insecticide approved for use on zoysia grass.

There are several types of larval worms that may arrive to feed on zoysia grass leaf blades. They include cutworms and sod webworms. Unlike white grubs, larval worms can have several life cycles during a given growing season are less predictable in their arrival. In addition, they are night feeders and hide in tunnels beneath your lawn during the day. Sod webworms leave a spidery web on grass blades that you notice early in the morning. Cutworms leave patches of cut grass. Larval worms can be controlled with a soil insecticide approved for use on zoysia grass. BT (Bacillus thuringiensis) is an effective natural product.

ARMYWORMS: Armyworms feed in masses throughout the day and night. They move quickly and can literally devour a lawn. Keep a lookout beginning in the late spring and through the growing season. Young larvae eat the edges of grass blades while the mature larvae eat the entire blade. Armyworms usually affect an entire subdivision/area at a time, so listen to your neighbors and state agencies for "armyworm alerts". The worst outbreaks of large populations usually occur from July through October. If they arrive on your lawn, immediately apply a soil insecticide approved for use on zoysia grass. Baccilus thuringiensis or BT is an effective natural product.

MOLE CRICKETS: Mole crickets are a major concern in the lower South in sandy soils. They occasionally damage zoysia grass, although they are most destructive to Bermuda grass and saint Augustine grass lawns. These horrendous burrowing crickets tunnel through the soil at night, loosening the sandy soil and disrupting grass roots. Mole crickets are active throughout the growing season but are most common when night air temperatures remain above 60 degrees. They can be controlled with a soil insecticide labeled for control of mole crickets and approved for use on zoysia grass.

CHINCH BUGS: Chinch bugs occasionally attack zoysia grass although they are most destruction to Saint Augustine and Centipede grass lawns. Damage usually appears as irregular patches of yellowing or wilted grass and is most common in July through September. To confirm their presence, but the top and bottom from a coffee can and pound it several inches into the yellow grass. Fill the inside of the can with several inches of water and maintain the water level for five minutes. The chinch bugs will float to the surface. If you find any, apply a soil insecticide labeled for control of chinch bugs and approved for use on zoysia grass.

FIRE ANTS: Fire ants are disheartening. I have tried almost every chemical available, and a number of home remedies and have had only average results. There are numerous entomologists working on the problem, so hopefully they will find a good cure soon.

If moles are tunneling through your lawn, they are probably after white grubs. Treat for white grubs in late July/early August and the miles will probably go away.

There are always more insects or pests that may plague your lawn. You might hear or read about ground pearls, nematodes, mites, viruses, and a long list of other potential problems. In general, don't worry. Just keep an eye on things and treat problems when you find them. Your lawn is tougher than you think.