WILT AND ROOT DISEASES OF ASCLEPIAS-TUBEROSA L

Chlorosis and wilting, followed by weak flowering or death, have been occurring in Asclepias tuberosa plants grown in Israel. Roots have bee n rotted and tuberous roots have shown dark lesions, sometimes with sc lerotia. A binucleate Rhizoctonia sp, was detected on 39% and Pythium intermedium on 23% of diseased samples. Other organisms were less prev alent. Wilting began 7 days after seedlings were inoculated with P. in termedium or the binucleate Rhizoctonia sp. or both, with disease inci dence ranging from 25 to 65% and disease severity index ranging from 0 .30 to 0.85 (scale of 0 to 3). Healthy tuberous roots inoculated with the binucleate Rhizoctonia sp. exhibited dry rot within 4 to 7 days, a nd irregular black sclerotia of the pathogen were present 2 weeks late r. This is the first report of either a binucleate Rhizoctonia sp. or P. intermedium occurring in A. tuberosa.