The oak leaf itch mite, Pyemotes herfsi, is cousin to the straw itch mite--a predatory mite often associated with stored grain and stored grain insects, and known to bite people who come in contact with infested grain (if you've never heard of this or straw itch mite, check out the Mallis Handbook of Pest Control). It was first reported in the U.S. from Kansas in 2004, a year when the mite was unusually abundant and resulted in thousands of biting complaints from people working and playing outdoors. That same year the mite was found in Nebraska, Missouri and here in Texas.
The mite's normal home is inside of leaf galls found on trees, and it is best known from marginal leaf curl galls caused by a midge (Macrodiplosis erubescens) on oaks. It may be equally at home in other types of galls on different trees. The problem with this mite seems to occur mostly in late summer and fall, when mites are prone to dropping from trees. Although the mites are principally predators on insects, if they come in contact with skin they will bite, leaving a painful, itchy welt. For more information on the mites click here for a Nebraska fact sheet.
|Bites from the oak leaf itch mite are typically seen on the neck|
or shoulder region of people who have been outdoors under
trees with galls.
These mites are very small (0.2 mm-long) and difficult to find. Bites, when they occur, tend to be around necks and shoulders, implying that the mites bite when they land, and do not crawl much on the skin before biting, like ticks or chiggers.
Complaints about mystery bites are one of the most common and frustrating calls for PMPs. But if the complaints come from a client who has been spending time outdoors, and especially under trees that are shedding their leaves, this is one critter to keep in mind.