Leaf Gall Mite on Arizona Walnut
Observed in Reynold's Canyon, Sierra Ancha, Gila Co., Arizona, USA. 4 June 2010. Host plant is Arizona Walnut, Juglan major.
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Hundreds of kinds of galls, each a different shape, size, location and color, can be found on plants growing within the sycamore woodlands in canyons of Arizona. Each gall type and plant species combination are caused by a different organism interacting with the host plant. This one can occasionally be found on foliage of Arizona Walnut. I believe this one is inhabited by gall mites. They are very small and can be seen only in fresh galls that are carefully opened and examined with high magnification - 15x minimum. The colony within the gall was initiated by a mated female mite while the leaf was just emerging from the bud. Several generations and possibly many dozens of mites are now contained within the blister. The blister formed from the underside of the leaf where a minute pore may be visible.