Effect of Crop Rotation and Metham-Sodium on Verticillium Dahliae

The fungus Verticillium dahliae Kleb. survives in soil for long periods, in the form of microsclerotia (MS) (Green 1969; Wilhelm 1955). In Israel the fungus was introduced into the Negev area with infected potato tubers (Krikum et al 1974). Following expansion of potato growing in the Negev, this pathogen became established in many fields in the region. The ordinary practice there is to grow potatoes only once every 3-4 years. Nevertheless, the fungal population increased and induced serious losses in potato yields although potato cultivars tolerant to V. dahliae (‘Desiree’and ‘Spunta’) have being used. In addition to the use of potato cultivars tolerant to V. dahliae, treatment of soil with metham-sodium (MES) was found to improve potato yields (Krikum et al 1974). This fungicide is used against V. dahliae because of its effectiveness, low cost, and ease of application to soil via the sprinkler irrigation system (Ben-Yephet et al 1983).