Kansas State University


Extension Entomology

Tag: oak leaf itch mite

Oak Leaf Itch Mite

–by Dr. Raymond Cloyd

We are still receiving many inquiries regarding the oak leaf itch mite (Pyemotes herfsi) and what can be done to avoid getting bitten. This is the first time in Kansas that the oak leaf itch mite has been a problem in successive years (2015 and 2016), which is likely associated with the mild winters we have experienced. Below is information associated with the oak leaf itch mite:


  1. The oak leaf itch mite may have originated from Europe based on documentation from 1936.
  2. There have been four major infestations of the oak leaf itch mite in Kansas: 2004, 2009, 2015, and 2016.
  3. The oak leaf itch mite is associated with the oak marginal leaf fold gall (Figure 1), which is produced by a midge gall-maker (Macrodiplosis erubescens).




Figure 1: Oak Marginal Leaf Fold Gall

  1. Mated females of the oak leaf itch mite prey on midge larvae.
  2. Females enter galls through openings and inject a potent neurotoxin that paralyzes midge larvae.
  3. A single female can produce between 200 and 300 eggs. Females deposit eggs into a pouch or ovisac that forms at the tips of the abdomen (Figure 2). Millions of individuals can be produced within a short period of time.



Figure 2: Oak Leaf Itch Mite Female Ovisac


  1. In seven days, immatures develop into adults (7 day life cycle). As a result, the oak leaf itch mite has one of the highest rates of population increase.
  2. Oak leaf itch mites can be dispersed via wind for hundreds of miles.
  3. Cooler temperatures and moist conditions may result in increased populations.
  4. Oak leaf itch mites emerge from the galls and fall from oak trees (primarily pin oak) from late July through fall. As many as 370,000 mites per day can fall from oak trees (yikes!).
  5. The mites bite anyone under oak trees with bite marks appearing 10 to 16 hours after exposure.
  6. In order to avoid bites, refrain from any activity under pin oak trees. Bites typically occur in the upper body region where clothing is loose; such as the neck, shoulder, and chest because the mites drop from the canopy of infested trees. The scratching, in response the bites, may result in secondary bacterial infections.
  7. People are susceptible to oak leaf itch mite bites when: 1) raking leaves, 2) sitting under infested oak trees, and/or 3) handling pets (dogs or cats) that have been around pin oak trees.
  8. Thorough bathing after exposure to infested oak trees, and washing clothing daily will reduce the number of bites.
  9. Oak leaf itch mite overwinters in protected areas or within leaves/leaf litter on the ground.
  10. Repellents such as DEET (N,N-diethyl-meta-toluamide) are not effective in preventing bites associated with the oak leaf itch mite.
  11. Wearing a Tyvek® suit (Figure 3) is one of the best ways to avoid getting bitten by oak leaf itch mites.



Figure 3: Tyvek Suit To Avoid Bites From Oak Leaf Itch Mite.


18. We do not recommend burning any pin oak trees.

For more information regarding oak leaf itch mites contact the Department of Entomology at Kansas State University (Manhattan, KS).


Oak Vein Pocket gall: Back with a Vengeance!

–by Dr. Raymond Cloyd

We have received numerous inquiries (in fact…LOTS) regarding gall-like growth on the underside of pin oak (Quercus palustris) leaves. In some cases, many pin oak trees have extensive galling on nearly all the leaves, with the leaves twisted or distorted. In fact, one tree on the Kansas State University (Manhattan, KS) campus, located behind Umberger Hall, is nearly 100 percent infested with this gall. I really think the gall makes the tree more attractive J. The culprit is the oak vein pocket gall, which is caused by the gall-midge, Macrodiplosis quercusoroca. Galls are elongated, pocket-like swellings on the lateral veins and mid-rib of pin oak leaves (Figures 1 through 3). The gall-making organism is a small fly called a midge (Family: Cecidomyiidae). Adults are 3.0 mm long and resemble small mosquitoes (but they are not mosquitoes so do not worry). Female midges attack newly developed leaves that are unfolding – just before they are flattened. After the eggs hatch, small larvae or maggots migrate to the lateral and mid-veins, and subsequently begin feeding. After several days, tissue forms and surrounds each larva. Full-grown larvae are white and approximately 2.0 mm in length. Development is completed by mid-spring to early summer. The larvae eventually emerge from the gall, fall to the ground, and overwinter or enter diapause (a physiological state of arrested development) until the next spring. There is one generation per year. There are no control measures for this gall. Remember, this is not the gall-former that the oak leaf itch mite feeds on…that is the marginal oak leaf fold galler (Figure 4).

Figure 1. Oak Vein Pocket Gall
Figure 1: Oak Vein Pocket Gall

Figure 2. Oak Vein Pocket Gall
Figure 2: Oak Vein Pocket Gall

Figure 3. Oak Vein Pocket Gall
Figure 3: Oak Vein Pocket Gall

Figure 4. Leaf Marginal Fold Gall
Figure 4: Leaf Marginal Fold Gall

I want to acknowledge Matthew McKernan; Horticulture Agent (Sedgwick County; Wichita, KS) for keeping me abreast of the situation (and sending images) regarding the oak vein pocket gall in south-western Kansas.