Apple rust mite
Aculus schlechtendali (Nalepa)
The vermiform adult has two pairs of legs at the front of its body (A). Brownish yellow in color, they are invisible to the naked eye, requiring a minimum magnification of 15X to be observed.
Most fruit-growing states and provinces in eastern North America.
Attacks apple mainly. Yellowish brown leaf discoloration occurs under very populated conditions (hundreds per leaf), sometimes accompanied by silvery-white blotches (B). Browning of the lower surface and drying out of the leaves occur as well (C; healthy foliage on left; damaged leaves, right). May occasionally russet fruit.
Preserve mite predators. Monitor populations on leaves during the summer with a 15X magnifying glass. Miticides can be used if populations are very high (greater than 200–500 per leaf), but lower numbers are valuable as prey for predator mites.
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