There are three basic categories of insects that damage grass. One is the insect that lives above ground and sucks the plant juice. The second is the kind that lives below the surface and feeds on roots. And the third is the insect that lives at the soil surface and feeds on the grass blades. The signs of symptoms of the first category is grass blades thinning out and turning brown. Whole patches of dead and dying grass in round to irregular shapes can appear. The most noticeable symptom of category two is that blades turn yellow and die in irregularly shaped patches. When a person grabs a handful of grass in these damaged areas, blades will come free and lightly out of the grass without any roots attached. Category three's symptoms are quite noticeable. Round bare areas can appear, with the grass chewed right down to root level.
LAWN INSECTS
Armyworms chew off the grass blades from below the surface and cause round, bare areas in a lawn. If there are many armyworms present, the grass will be chewed off right to the soil level. Armyworms are yellowish white and have an upside-down Y on their heads. For chemical control use acephate, diazinon, chlorpyrifos, or carbaryl.
Billbugs feed on grass roots and create small circular patterns of damaged grass that turns yellow and brown. Dead sections of grass will easily lift away from the soil. There are many different species of billbugs that attack different varieties of grass. For chemical control use diazinon.
Chiggers do not do much damage to a lawn, but they are an extreme nuisance to lawn owners. They are not insects, but are spider mites that lay their eggs in soil. After hatching,the larvae crawl onto grass blades and latch on to any passing person or animal. For chemical control use diazinon or chlorpyrifos.
Cinch Bugs damage lawns by sucking the juice directly from the leaves. Generally these insects are widespread and can be discovered upon close examination of grass blades that have turned yellow in distinct circular patches. They particularly enjoy St. Augustine grass, but Kentucky bluegrass and bent grass are also affected. For chemical control use propoxur, isophenphos, diazinon, chlorpyrifos, or NPD.
Crane Flies lay eggs that produce grubs which feed on grass blades. This causes patches of grass to disappear, usually from the edge of the lawn. Sometimes a brownish paste will cover an area with a large concentration. Crane fly grubs are brown-gray and about an inch long. For chemical control use diazinon.
Cutworms are extremely difficult to spot, not only because they live and stay far down in the root system, but because the appearance of the damage they cause is similar to that of so many other diseases and ailments. Cutworms eat the tender roots of the plant and this causes dead brown spots to form in round and irregular patches. If a person were to spill gas or use too much fertilizer in an area, the effect would be the same as the damage done by cutworms. For chemical control use acephate, carbaryl, diazinon, or chlorpyrifos.
Root-Feeding Nematodes feed on lawn roots and cause grass to grow slowly and to respond poorly to watering and fertilizing. Often the grass looks stunted and yellowed with dead and dying areas. Sometimes this problem is confused with fertilizer burn, soil deficiency, and poor aeration. The grass roots may be swollen, stunted, bushy, and dark in color or missing altogether. There are many thousands of kinds of nematodes, but only a few damage lawns. Complete diagnosis will require the assistance of a competent nematologist. Likewise, for control, only a professional should complete any kind of necessary application.
Sod Webworms live in the grass root system, but they surface to devour leaves and stems with an insatiable hunger. Dead patches from one to two inches in diameter appear among otherwise healthy, normally growing grass. Many birds feeding regularly on the lawn can indicate a high concentration of this insect. Sod worms are not as easy to spot as cinch bugs, but they can be discovered by examining a few two-inch clods of grass taken from various portions of a suspect area of lawn. For chemical control use carbaryl, chlorpyrifos, diazinon, acephate, isophenphos, propoxur, NPD,or trichlorfon.
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