Along with mosquitoes, yellow jackets and horseflies that swarm, each in their own season, a relative of the scorpion lurks in brush and foliage, waiting for its next meal. In addition to being a nuisance pest, ticks can carry two illnesses, Lyme disease and Rocky Mountain spotted fever. Not all insect repellents work against these nasty little arachnids, but a few can save the summer for a gardener.
Because their shells do not grow as they do, ticks go through several "molts" where they shed old body coverings and grow new ones; from larvae to nymph to adult. At each stage, the growing tick needs a host to provide nourishment. Ticks are most active during the spring and early summer, but ticks feed until temperatures drop below 40 degrees F in fall; larvae attach mainly to small animals but nymphs and adults feed on larger prey: dogs, deer and humans. Adult females lay eggs in their second year of life and die after reproducing.
Repellents turn ticks away by means of some unpleasant quality or they make them ill. Two ticks are the primary targets of repellents: the wood tick, "Dermacentor variabilis,"also called dog tick, and the blacklegged tick, "Ixodes scapularis," which is also called deer tick. Three other types of ticks, lone star tick, brown dog tick and winter tick, afflict dogs, deer and other animals but are not common human pests. The wood tick can transmit Rocky Mountain spotted fever and tularemia (rabbit fever) to humans. The deer tick carries Lyme disease. Both may also transmit ehrlichiosis, a bacterial disease.
Ticks jump from foliage to attach to legs as their potential host passes by. They then crawl upward to find a sheltered attack site, often on the head or neck. Bites may not even be noticeable; gardeners should wear long sleeves and slacks tucked into socks when working in areas with long grass, brush and shrubs to protect against ticks. Sprays should be applied to clothing or skin in a well-ventilated area according to label directions; all sprays are not the same.
N,N-diethyl-m-toluamide, marketed as DEET, is the most effective and commonly used broad-spectrum repellent available. Over 200 products, including many sprays containing DEET, are currently registered with the Environmental Protection Agency. According to a study by the Connecticut Agricultural Experiment Station (CAES), DEET is more effective against wood ticks than deer ticks. It should be sprayed on clothing, particularly shoes, stockings and pant legs. Repellents containing 20 to 40 percent DEET were found to work as well those with higher DEET concentrations.
CAES also lists about half a dozen products that include permethrin, a synthetic pesticide that also has repellent properties. Sprayed on clothing, its ability to kill ticks may last through several washings. Products typically contain 0.5 percent permethrin and are marketed as sprays in lawn and garden or camping stores.