INSECTS
Symptom: Brown turf that becomes loose enough to lift like a mat.
Culprits: White grubs, a catch-all name for root-chomping beetle larvae, including june bugs, Japanese beetles, and masked chafers. To be sure that's what you've got, cut a square foot of infected turf and roll it back, looking for pale, half-inch- to inch-long C-shaped bugs. If you find more than six, treat the turf.
Solutions: Grubs are the biggest threat to lawns, and pesticides formulated with imidacloprid are proven effective. For an organic fix, spread powdered milky spore or lay down beneficial nematodes-microscopic worms that will feed on the grubs if they're present. With nematodes, timing the application with their life cycle is critical, so be sure to follow the directions on the box exactly. Both milky spore and nematodes can be ordered from some garden centers or online (gardensalive.com).

Symptoms: Irregular-shaped patches of brownish-yellow grass.
Culprits: Chinch bugs, gray-black, quarter-inch-long insects that suck moisture from grass and are most likely to attack St. Augustine and zoysia grasses in the South and Kentucky bluegrass in the North. To spot them, bury an empty coffee can, with both ends removed, at the edge of the affected area and fill it with water. The bugs will seek out the moisture, then float to the top. If you see more than 10 after 20 minutes, you should address the problem.
Solution: Chinch bugs live on the surface, among thatch, so dethatching will reduce their numbers. To eradicate them completely, look for an appropriate insecticide with a pyrethroid ingredient. Longer-term, overseed with chinch-bug-resistant grasses.

Symptom: Patches of thin lawn with blades chewed off at the base.
Culprits: Sod webworms and tropical sod webworms, hairless cream-to-gray spotted caterpillars that grow into small, buff-colored moths at maturity. The tropical species that thrive in warm southern climates cause the most harm. To check for webworms, mix two tablespoons of mild detergent with two gallons of water; pour it over the infested turf. Any larvae will float to the top.
Solutions You can try flooding your lawn to drown them. Or choose an appropriate insecticide; in an organic product, look for the ingredients azadirachtin or spinosad. With extreme cases of tropical webworm infestation you may need to replace the turf with a resistant grass mix.

TIP: If dogs regularly make a pit stop of your lawn, keep a hose or water bucket nearby. Dog urine is high in nitrogen, which can "burn" turf, creating a good-sized yellow patch. The best fix is immediate action: Flush the area ASAP with water to dilute it. Once badly burned, grass won't come back on its own-you'll have to rake out the dead stuff and reseed.

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