Sunflower Diseases in Some Growing Areas of Thailand

Abstract

Sunflower diseases found in Nakhon Ratchasima, Khon Kaen, Nakhon Pathom and Chon Buri during Mar, 1987 – April, 1988 were leaf spot and leaf blight including lesion on stem, branch, head, sepal, petal and bract infected by Alternaria spp, while the rest of them were leaf spot caused by Septoria sp. “downy mildew by Plasmopara sp., rust by Ureds sp., base and root rot by sclerotium sp.” and head and dry rot of seeds by Cladosporium sp. However, there were other different symptoms which causal agents have not yet been identified such as, yellow and leaf blight similar to a mineral deficiency, mosaic, yellow, and distortion by virus or mycoplasma, and root – knot by nematode, and the last symptom indicating here Phomopsis blight. Among these pathogens, Alternaria spp. And Septoria sp. were observed to be the most destructive one causing substantial loss to sunflower at Suwan Farm, Pakchong in Nakhon Patchasima. It was also noticed that more than one species of the Alternaria spp. infected sunflower in the test plots at Suwan Farm such as, A. Zinnaie and A. helianthi.