Plant Disease Diagnostic Lab Highlights

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.

Recent diagnostic samples of agronomic crops have included Lepto leaf spot and alfalfa weevil injury on alfalfa; leaf streak on orchardgrass; powdery mildew on wheat; and frogeye leaf spot on tobacco transplants.

Figure 1: Red thread is right on schedule in home lawns this spring; the disease is most active in April and May in Kentucky. Circular patches of blighted foliage in bluegrass or fescue lawns appear light tan rather than red. The reddish (or pink) color of the causal fungus, Laetisaria fuciformis, is only visible under conditions of prolonged wetness (Photo: Julie Beale, UK).

On fruit and vegetable crops, we have diagnosed Phomopsis leaf blight, anthracnose (crown rot and fruit rot phases), Rhizoctonia fruit rot, common leaf spot, and the black root rot complex on strawberry; leaf curl and lesser peachtree borer injury on peach; fire blight and frogeye leaf spot on apple; Pythium root rot on cabbage; root knot nematode on cucumber; angular leaf spot on squash; bacterial canker, Pythium root rot, and powdery mildew on tomato.

On landscape and turf samples, we have seen Fusarium canker on rose-of-sharon; white peach scale, and Leucostoma and Botryosphaeria cankers on ornamental cherry; Endothia canker on beech; Rhizosphaera needle cast, Dothistroma needle blight, and spider mite injury on spruce; Diplodia tip blight and Dothistroma needle blight on pine; and red thread on bluegrass (Figure 1).

 

By Julie Beale and Brenda Kennedy, Plant Disease Diagnosticians

 

 

 

 

Posted in Plant Disease Diagnostic Lab