The Missouri Department of Conservation (MDC) is getting reports of oak leaf itch mite activity from around Missouri, especially western parts of the state and Kansas.
Unfamiliar with these creepy, scratchy crawlies? These nearly microscopic mites prey on midge larvae that form marginal fold galls on oak leaves. In late summer, as midge larvae exit the galls and drop to the soil for overwintering, mites also drop from the leaves in huge unseen "mite showers."
People who spend time under oak trees (especially pin oaks) are being bitten, but mites can also be carried long distances on the wind and can be blown through screens on open windows. Bites are similar to chigger bites but are typically on the head, arms and upper body, rather than on the legs and lower body, where chigger bites are more common.
Haven't heard about them before or recently? This mite was first recognized in the Midwest when it occurred at outbreak levels in 2004-06. It has been mostly absent since then, until reappearing in Kansas last year. MDC Forest Entomologist Rob Lawrence expressed his opinion in a recent email warning the severe freeze of April 2007 may have knocked them back. That freeze resulted in widespread killing of foliage that had flushed early that year, and likely either directly killed itch mites or killed one of their primary prey, the marginal fold gall midge. This gall has been difficult to find in recent years, but is likely recovering.
Why should one care, and why now? First, we've had a report in Jefferson City of classic bite symptoms from Sept. 28 after working under an oak tree, which was the end of our typical late summer temperatures. In the past, many reports come from mid- to late summer, as mites are dropping from trees. One of the more famous cases was most of the crowd watching a high school football game in eastern Kansas getting afflicted, the stands being near a number of oak trees. Studies have estimated the number of mites dropping from large pin oak can exceed 300,000 mites per tree per day.
So they are here, which brings us to the second reason to care. Fall leaf-raking season is just beginning. A second surge of reports generally come in during October and November after leaf drop, when folks are raking leaves and presumably stirring up mites again. The mites can continue to be a problem until we get colder weather. Reports of mite bites have occurred into December, coupled with mild days.
What to do? As with chiggers, spray-on insect repellents with DEET over areas most likely to catch them. Wear a broad-brim hat and treat it, too. Especially consider this if working under oak trees or with their leaves and brush. Not to state the obvious, but bathing - and changing and washing clothes - after exposure to mite habitats is highly recommended. Areas where periodical cicadas emerged earlier this year may be at risk of larger itch mite populations. However, MDC is getting many reports of itch mites in Southwest Missouri where periodical cicadas did not emerge. If you get bitten, Benadryl and calamine lotions are recommended to help relieve itching. Folks bitten in the past report the bites seem to take longer to go away than typical chigger bites; for many, about three weeks for the spots to completely disappear, and the first week being pretty itchy.
Lastly, be aware and share the news. A friend, coworker or acquaintance will appreciate knowing where the mysterious bites have come from (should they be unlucky enough to get them). After all, they are temporary and much less serious than shingles.