The following plant disease highlights from the University of Kentucky Plant Disease Diagnostic Laboratories represent recent sample submissions from field crops, fruit, vegetables, and ornamentals.
Diseases and other problems diagnosed on agronomic crops during the past week have included gray leaf spot, Diplodia leaf streak, southern corn rust, anthracnose, bacterial stalk rot, and stinkbug injury on corn; common leaf spot, Lepto leaf spot, Rhizoctonia crown rot and web blight, and summer black stem on alfalfa; leaf streak on orchardgrass; powdery mildew and Cercospora leaf spot on red clover; Phytophthora root rot and soybean cyst nematode on soybean; angular leaf spot, black shank, soreshin, Fusarium wilt, frogeye leaf spot, bacterial soft rot, tomato spotted wilt virus, scald (from saturated soils), low pH symptoms, and potassium deficiency on tobacco.
On fruit and vegetable samples, we have diagnosed black rot on grape; crown gall on blueberry; scab, bacterial spot and brown rot on peach; Rhizoctonia root/stem rot on bean; Pythium and Rhizoctonia root rots on Brussels sprouts; bacterial spot and southern blight on pepper; bacterial spot (Figure 1), early blight, Septoria leaf spot, leaf mold, tomato spotted wilt virus, spider mite infestation, ripe rot, and blossom end rot on tomato. Numerous cucurbit diseases were also diagnosed, including: Pythium and Rhizoctonia root rots (cucumber, melon); Alternaria leaf blight (melon); bacterial wilt (melon); Cercospora leaf spot (cucumber); powdery mildew (cucumber, watermelon); watermelon mosaic virus, bacterial soft rot, poor pollination, Choanephora rot and downy mildew (squash).
Ornamental and turf samples included aster yellows on coneflower; bacterial blight on daisy; Pythium root rot on chrysanthemum; powdery mildew, Cercospora leaf spot, and bacterial blight on peony; Rhizoctonia root/stem rot on zinnia; anthracnose on iris; Cercospora leaf spot and southern blight on dahlia; Botryosphaeria dieback on sumac; Cytospora canker on willow; spot anthracnose on linden; anthracnose on oak; Rhizosphaera and Stigmina needle diseases on spruce; brown patch on fescue; anthracnose on bluegrass; Pythium root dysfunction, take-all, anthracnose, and Pythium blight on bentgrass.
By Julie Beale and Brenda Kennedy, Plant Disease Diagnosticians