Wednesday, November 5, 2014
Oak trees in and around Lawrence are reportedly dropping more than acorns and leaves this fall, and individuals who plan to spend time outdoors should be on the lookout.
Oak leaf itch mites — tiny eight-legged creatures that feed on insects in the tree canopy — drop from oak leaves in late summer and fall. The mites have been known to bite humans when they come into contact with bare skin.
Oak leaf itch mite bites typically result in a rash or raised welts similar to chigger bites. The bites are characterized by their location on the body, most often occurring on shoulders, neck and upper body because of the nature of their fall. They can be carried by wind, and may also bite hands and exposed arms of gardeners who are handling leaves or infested plant material.
Protection is the best bet for gardeners and outdoor enthusiasts who plan to spend time raking leaves or enjoying the fall weather under oak trees.
Wear tightly woven long-sleeved shirts and pants for outdoor activities. Limit the amount of time spent around possibly-infected oak trees.
Wash clothes and bathe immediately after outdoor activities are complete. Gloves may protect hands for those who will be handling leaves and plant material.
DEET-based repellents were originally recommended for protection as well, but have shown mixed results.
Insecticides are ineffective because mites remain protected inside leaf tissues until they drop and because of the mites’ short life cycle.
Individuals who get bit by itch mites can treat bites similarly to other insect bites. The US Centers for Disease Control and Prevention lists calamine lotion, oral histamines and over-the-counter hydrocortisone products for relief. Sensitive individuals may wish to seek medical treatment.
Itching may last a week or more depending on the person, and scratching bites may lead to secondary infection.
Oak leaf itch mites primarily feed on oak gall midges. Oak gall midges are named for the growth, or gall, that forms around the area where the midge is feeding on the leaf. One of the most common oak galls is known as the marginal leaf fold gall. As the name describes, these galls are characterized by a raised area along the leaf margin that looks like the edge of the leaf is folded over. Oak leaf itch mites enter the galls to prey on midges inside.
Fortunately, oak leaf itch mites only live for about a week. Unfortunately, they can have multiple generations in a year. Oak leaf itch mites are likely to be more prevalent in years when there are heavy gall populations.
The first reports of oak leaf itch mites in the United States were in Kansas and Nebraska in 2004. The mites have since been reported in much of the Midwest and as far east as Pennsylvania, and are believed to have originated in Europe. Like many exotic pests, they came into the United States on infested plant material. They have also been recorded in Australia, India, Egypt and Chile.
— Jennifer Smith is a former horticulture extension agent for K-State Research and Extension and horticulturist for Lawrence Parks and Recreation. She is the host of “The Garden Show” and has been a gardener since childhood. Send your gardening questions and feedback to Lawrence Living@ljworld.com.