Oak Leaf Itch Mites - A Brief Informational Sheet
- Chao Wu
- Sep 24, 2015
- 3 min read
Note: The things you see clinging to the tree branches in the image above are cicada exuviae (shells). I am only using this oak tree picture as a coverphoto, not as a representation of leaf mites.
Oak Leaf Itch Mites (Pyemotes herfsi)
Developed for Kansas, which is seeing a large number of mites at this time.
Oak leaf itch mites (or oak mites) are a close relative of the straw itch mite (P. tritici) and are very difficult to see with the naked eye. Generally, individuals only reach about 0.2mm in length. Under the microscope, individuals are a brownish-red in coloration. The species’ existence was first recorded in Europe. However, they have since been identified in many countries of the Old World, along with a few countries in the New World. Ironically, one of the first outbreaks occurred in Kansas, followed by a second outbreak a few years later (1997 and 2004 respectively). Like mosquitoes, females are the ones that actually inflict the bite on humans. They inject a toxin from their saliva which allows for feeding. Interestingly enough, the species generally feeds on other insects, with oak midge larvae being the main host here in the United States. Outbreaks here in the US have generally been attributed to changes in oak midge larvae populations (Broce, Zurek and Kalisch et al.). The species favors moist, cool conditions (which is exactly what occurred in early summer this year in Eastern Kansas). In addition, there have also been reports that these feed on periodical cicadas (Magicicada sp.) as well. Due to the fact that the Brood IV 17 year cicadas emerged this year in Kansas, there may have been an increase in sustenance and numbers of mites. However, this is purely hypothetical and is not substantiated via research by me or anyone else.
Now, I would like to dedicate a short section on the life history of the species. Males emerge with the sole purpose of mating. After doing so, they die (without biting or feeding). Female mites, after mating, will find a gall (an abnormal grow on a plant due to insects and other organisms inside) and enter it to attack the insect larvae hidden within the gall. She then attaches, paralyzes and feeds on the larvae until her own offspring emerge, sometimes in as little as one week (PSU Entomology). Presumably, the offspring emerge as adults.
According to the CDC, the Kansan outbreak in 2004 caused 54% of the population of Crawford County (~19,000 individuals) to suffer bites. Bites generally do not itch for at least half a day to one day before itching. Due to their small size, those bitten often do not realize or “feel” the mite during the “biting” process. The result of the bites is rashes which are reddish in color and have a yellowish, blister-like circle in the center. Scratching may cause infection, so it is best to avoid it if at all possible. If infection does occur, make sure to keep the area clean with proper sanitization. Calamine, Benadryl and other itching lotions can also help soon the irritation. Seek professional help if the itching is too unbearable or if it appears to worsen over time. While the bites are generally non-lethal, it is important to be cautious to avoid exposure to more bites, along with secondary infections which may occur as a result of scratching.
Control of this species is difficult, especially since chemical treatment does not often enter into the galls the adult females are hiding within (PSU Entomology). Wearing insect repellent with DEET may be useful, but not necessarily 100% effective. Limiting yourself to areas underneath large trees and avoiding forested and wooded areas are also good ways to avoid bites (it might be nice outside, but maybe don’t read under the trees)! Also, removing any clothes you have worn outside to wooded areas and washing them can help decrease spread. Finally, I encourage all to take a nice long shower to wash off any lingering mites after a day trekking near any large trees, whether in your yard, on your campus or deep in the forest!
Chao “Jimmy” Wu
Student of Biological Sciences
Boston University
Email: jwmantid@yahoo.com
For More Information: http://www.cdc.gov/mmwr/preview/mmwrhtml/mm5438a3.htm
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