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 diagnosed on agronomic crops during the past week have included southern rust, anthracnose, Diplodia and Fusarium stalk rots, Diplodia ear rot, and pollination problems on corn; anthacnose, Rhizoctonia and Ascochyta leaf blights, and rust on orchardgrass; anthracnose, sudden death syndrome, frogeye leaf spot, soybean cyst nematode, and potassium deficiency on soybean; black shank, angular leaf spot, frogeye leaf spot, brown spot (Figures 1 & 2), manganese toxicity, and frenching on tobacco.
Figure 1. Brown spot, caused by the fungus Alternaria alternata, is a common late-season tobacco disease in humid years. In this sample, extensive spotting had developed on lower leaves. (Photo: Julie Beale, UK)
Figure 2. Brown spot also causes spotting on tobacco stalks. (Photo: Julie Beale, UK)
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On fruit and vegetable samples, we have diagnosed Phomopsis fruit rot on grape; bitter rot on apple; Cercospora leaf blight, and Pythium and Rhizoctonia root/crown rots on bean; Cercospora leaf spot and powdery mildew on melon; downy mildew on pumpkin; anthracnose and vine borer injury on squash; early blight, Septoria leaf spot, leaf mold, Rhizoctonia foliar blight, and tomato spotted wilt virus on tomato.
Ornamental and turf samples included Pythium stem/root rot on petunia; Pythium root rot, Fusarium wilt, web blight, and rodent injury on chrysanthemum; downy mildew on impatiens; black root rot on holly; black spot on rose; anthracnose on birch; spot anthracnose on dogwood; anthracnose, Actinopelte leaf spot, powdery mildew, jumping oak gall, and bacterial leaf scorch on oak; elm yellows on elm; Cylindrosporium leaf spot on walnut; powdery mildew and summer patch on bluegrass; brown patch on fescue; basal anthracnose, Pythium root dysfunction, and heavy thatch buildup on bentgrass.
Additional Resources
For information about foliar diseases in tobacco, refer to following UK Extension publication: Burley and Dark Tobacco Production Guide (ID-160)
By Julie Beale and Brenda Kennedy, Plant Disease Diagnosticians
Kentucky Pest News 