Leaf Gall Mite on Box Elder
Aceria negundo
On new spring growth of Western Box-elder, Acer negundo, at Washington Park, northern Gila Co., Arizona, USA. 14 June 2015. Habitat is mixed riparian, oak and conifer woodland. These wart-like galls are located on the upper surface of the leaf.
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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. The mites 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 each gall.
Box elder can be found at a wide range of elevations in Arizona, 1200m to over 2200m. These mites initiate their galls in fresh new growth, the timing of which is highly dependent on elevation. A worth while project would track these mites by temperature and elevation as a proxy for how they might respond to changing climate.