Integrating Onion in Crop Rotation to Control Sclerotium rolfsii. O. Zeidan, Extension Service, Hadera, Ministry of Agriculture, The Hebrew University of Jerusalem, Faculty of Agriculture, Rehovot 76100, Israel. Y. Elad, Research Associate, Y. Hadar, Lecturer, and I. Chet, Professor, Department of Plant Pathology, The Hebrew University of Jerusalem, Faculty of Agriculture, Rehovot 76100, Israel. Plant Dis. 70:426-428. Accepted for publication 24 August 1985. Copyright 1986 The American Phytopathological Society. DOI: 10.1094/PD-70-426.

Including onions in crop rotation reduced damage in crops susceptible to Sclerotium rolfsii. In peanuts grown after onions, disease incidence was reduced 62% and pod yield was increased 15–52% in field experiments. Onion cultivars showed distinct differences in their ability to reduce the incidence of S. rolfsii infection. Disease suppression detected 4 mo after planting onions in infested soil lasted for a year. Sclerotia buried in an onion field were 42% less viable than the control. Onion bulb extract or root exudates inhibited both sclerotial germination and mycelial growth. The inhibitory compound, with a molecular weight of less than 5,000, was heat-sensitive. Integrating onions in crop rotation in S. rolfsii-infested fields is potentially an inexpensive means of disease control.