Credit: Whitney Cranshaw, Colorado State University, Bugwood.org
Credit: F. Peairs, Colorado State University, Bugwood.org
Credit: Jeffrey Hahn, University of Minnesota
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Two-spotted spider mite Microsphaeria penicillata
White to yellow stippling on foliage; leaves can be off-green
Heavy infestations will cause leaves to turn white, yellow and ultimately grayish bronze; premature leaf drop may occur
Webbing may be present, especially when heavily infested
Mites usually appear in late June to August; they are more prevalent in hot, dry weather
Adult spider mites are small (approximately 1/50 inch long) and are hard to see; they are yellow to dark red with dark spots (need magnification to see)
Non-selective herbicide injury (Round-up, Kleen-up, and other glyphosate products)
Yellowing, wilting, browning leaves and eventual death of foliage and plants
Damage usually appears first in new tissues
Shrubs sprayed during the summer or fall may not have noticeable injury until the following season when leaves appear as stunted, narrow, strap-like, and chlorotic
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Credit: M. Grabowski, University of Minnesota
Credit: M. Grabowski, University of Minnesota
Credit: Paul Bachi, University of Kentucky Research and Education Center, Bugwood.org
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Verticillium wilt Verticillium dahliae
Leaves on one to several branches turn red to yellow, wilt, die and fall off
Dark olive to gray streaks are often visible in the sapwood if the bark is peeled back
Symptoms may appear in several branches or in the entire shrub
Symptoms are often most obvious in late summer and autumn but can occur throughout the growing season