Overgrown weeds create habitat for chigger mites

A caller's daughter recently developed blister-like chigger bites after being in sagebrush. Mice, rats, rabbits, ground squirrels and other mammals, and even birds and reptiles, can host chiggers. When people go through areas where there are or have been infested animals, chigger mites can hitch a ride, then feed.

"Chigger mites are about 1/20 inch long, usually bright red, have hairy bodies and travel rapidly. The larval stage has three pairs of legs whereas the nymph and adult stage have four pairs of legs. They are usually encountered in late spring and summer in areas where weeds have overgrown. They lurk on grass stems, leaves and shrubbery, usually in damp, shaded spots close to the soil. The preferred feeding locations on people are parts of the body where clothing fits tightly over the skin such as around the belt line, waistline and under socks, or where the flesh is thin, tender or wrinkled such as the ankles, in the armpits, back of the knees, in front of the elbow, or in the groin" (Chiggers, HYG-2100-98, by William F. Lyon, Ohio State University).

Chigger larvae do not burrow into the skin, nor suck blood. To feed, they find a hair follicle or a skin pore on the host and inject enzymes that break down skin tissue, allowing the chigger to suck up the dissolving tissue. They can feed for 24 to 96 hours. Bites are slightly larger than mosquito bites and intense itching can last for up to two weeks. Any welts, swelling, itching or fever will usually develop three to six hours after exposure. Scratching a bite may break the skin, resulting in secondary infections. Chiggers are not known to transmit any disease in this country. After feeding, chiggers drop from the host.

Adult chiggers are harmless to humans and arebeneficial predators on other insects and mites. It is only the first larval stage that feeds on vertebrate hosts. To prevent chigger bites, keep weeds on your property cut down and mow the lawn often. Wear pants tucked into socks or boots. Use insect repellent on skin and clothing following label directions when going into areas of heavy grasses, weeds or brush. Avoid sitting or lying on lawns or in patches of vegetation. Keep moving and stay on roads and trails when out hiking. Wash field clothes in hot soapy water before wearing them again. Expose clothes after washing to hot sunshine to reduce lingering chiggers. Be chigger prepared!

• JoAnne Skelly is the Carson City/Storey County Extension educator for University of Nevada Cooperative Extension and may be reached at skellyj@unce.unr.edu or 887-2252.