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.
Diagnostic samples of agronomic crops from the past week have included common rust, southern rust, Physoderma brown spot, gray leaf spot, thrips feeding injury, potassium deficiency, and soil compaction symptoms on corn; leaf streak on orchardgrass; Pythium damping off/root rot on hemp; Phyllosticta leaf spot and potassium deficiency on soybean; angular leaf spot, frogeye leaf spot, Pythium root rot, black shank, soreshin, Fusarium wilt, tomato spotted wilt, weather fleck, boron deficiency, manganese toxicity, symptoms related to low soil pH, sunscald, and transplant shock on tobacco.
On fruit and vegetable crops, we have diagnosed black rot, anthracnose, and Phomopsis fruit rot on grape; Phytophthora root/crown rot on blueberry and raspberry; bitter rot, cedar-apple rust, and plum curculio injury on apple; potyvirus on bean; anthracnose and powdery mildew on cucumber; common rust, northern corn leaf blight, and gray leaf spot on sweet corn; Pythium and Rhizcotonia root rots and bacterial leaf spot on pepper; powdery mildew on squash; Phytophthora crown rot on rhubarb; Septoria leaf spot, bacterial leaf spot, bacterial speck, early blight, Pythium root rot, southern blight, Fusarium wilt, root knot nematode, tobacco mosaic virus, and tomato spotted wilt on tomato; anthracnose and Phytophthora fruit rot on watermelon (Figure 1).
Figure 1: Visible white sporulation of Phytophthora capsici on rotting watermelon fruit. This pathogen can cause crown rot as well as fruit rot of all cucurbit crops under warm, wet conditions. (Photo: Brenda Kennedy, UK)
On landscape and turf samples, we have seen Pythium root rot on candytuft; Pythium and Rhizoctonia root rots on catharanthus; bacterial leaf spot on zinnia; Phytopthora crown rot on liriope; anthracnose on ash, birch, and oak; Cercospora leaf spot on cherry; cedar-quince rust on hawthorn; spot anthracnose and powdery mildew on dogwood; Phyllosticta leaf spot on maple; Cercospora leaf spot and an anthracnose-like leaf spot on ginkgo; Phytophthora crown rot on taxus; Rhizosphaera needle cast on spruce; Pythium root dysfunction and layering on bentgrass; summer patch on bluegrass; and brown patch on fescue.
By Julie Beale and Brenda Kennedy, Plant Disease Diagnosticians
Kentucky Pest News 