It is impossible to keep track of all the insects that live in a well-grown fescue lawn. The most common inhabitants are usually crickets, beetles, grasshoppers, millipedes, and worms. Some of these insects feed on the grass blades, some feed on grass roots, and some feed on each other. Usually, Fescue will grow faster than the average insect can eat and you don’t have to worry. There are, however, a few classes of insects that can increase in populations large enough to harm your lawn. These can also be treated fairly easily with soil insecticides and natural products like BT. 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 lawn. If you take a drive around town, you will probably pass countless lawns that fit that description. The problem is, only around ten in a thousand lawns will have an insect problem. Lawns are finicky and irregular brown patches pop up for different reasons. One of the most common is drought. You might think your lawn in 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, it is more productive to first look for another cause first. Then, wait to see if the troubled lawn area expands. Only then should you worry about treating with soil insecticide. Here is a list of problem insects.
White grubs: These are one of the most common insect pests for Fescue grass. White grubs are the larval, soil-inhabiting form of several different types of beetles. The most notorious beetle in the South is the Japanese Beetle. White grubs can be controlled with a granular soil insecticide applied in late July/early August according to the labeled directions. Milky Spore is a natural product that effectively kills the white grubs. The effective ingredient in Milky Spore (Bacillus popilliae) will remain active in your soil for many years – a good long term solution to white grubs
Billbugs: are black, hard-shelled beetled with a curved snout like an 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 that feed on fescue 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 Fescue grass.
Armyworms: Armyworms are another type of larval worm that 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 sub-division at a time, so listen to your neighbors and state agencies for "Armyworm alerts". The worst outbreaks of large populations usually occur from July to October. If found, apply a soil insecticide approved for use on Fescue grass. Damaged lawns can usually be revived with careful irrigation.
Chinch bugs: A notorious problem in the South. Infected lawns usually have irregular patches of yellowing or wilted grass in sunny areas. Chinch bug problems are most common in July through September. To confirm their presence, cut the top and bottom from a coffee can and bound it several inches into the yellow grass. Fill the insecticide of the can with several inches of water and maintain the water level for 5 minutes. The chinch bugs will float to the surface. Once you have located them, treat the area with a soil insecticide labeled for control of chinch bugs and approved for Fescue grass.
Mole crickets: Mole crickets are a major concern in the lower South in sandy soils. These horrendous burring 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. Damage usually appears as if someone cultivated areas of your lawn. They can be controlled with a soil insecticide labeled for control of mole crickets and approved for use on Fescue grass.
Moles: if moles are tunneling through your lawn, they are probably after white grubs. Treatment for white grubs in late July/early August is likely the easiest way to get rid of moles.