Tuesday, August 23, 2011

Three-leaf Sumac and eriophyid mites

Lower Leaf Surface
Upper Leaf Surface
 If you have a three-leaf sumac, Rhus trilobata, and it takes on a purple cast as seen in the above photo it most likely has an infestation of eriophyid mites. These tiny carrot-shaped creatures feed on the leaves and cause them to change color. With some trees, they cause the leaves to curl or roll. They are very hard to see as they are one-fifth of a millimeter in size (twenty-five millimeters in an inch).

A spray of plain or soapy water usually is sufficient to wash these six-legged critters off the leaves. Be sure to wash both sides of the leaves paying more attention to the underside. See http://www.coopext.colostate.edu/TRA/PLANTS/erio.shtml  for more info on these mites.
The orange carrot shapes to the left of the pin, the black line, are the mites.

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