Epidemiological Factors of Sugar Beet Powdery Mildew

Abstract

RUPPEL, E. G., and B. J. TOMASOVIC. 1977. Epidemiological factors of sugar beet powdery mildew. Phytopathology 67: 619-621. Susceptibility to powdery mildew (caused by Erysiphe sugar beet fields did not infect sugar beet in the greenhouse. polygoni) in sugar beet inoculated 2, 4, 8, 12, and 16 wk after Vegetative mycelia or conidia of the fungus remained planting increased with plant age. Of 33 plant species infectious in sugar beet leaf debris buried outdoors in soil for representing 19 genera in nine families, only Beta 60, but not 90, days. Infected leaf debris stored at room atriplicifolia, B. lomatogona, B. macrocarpa, B. macrorhiza, temperature, in a refrigerator at 3-4 C, or in a protected area B. maritima, B. patula, B. trigyna, and B. vulgaris (red beet, outdoors over winter was noninfectious when tested after 60 sugar beet, Swiss chard) were highly susceptible to the fungus days of storage. Erysiphe polygoni-infested seed yielded from sugar beet; B. patellaris was highly resistant. Atypical healthy seedlings, and inoculum prepared from infested seed infection spots occurred on senescent leaves on one was noninfectious to sugar beet. The brief life of the fungal Chenopodium capitatum and two Rumex crispus plants, but vegetative stage, the absence of the perfect stage, specificity the hyphae did not spread, sporulation was minimal or for the genus Beta, and the yearly sequential spread of the nonexistent, and the fungus ultimately disappeared. disease support the theory that overwintering of the fungus Powdery mildew conidia (Erysiphe spp.) from Amarathus mainly occurs in the southwest and that conidia are carried retroflexus, R. crispus, and Solanum sarachoides growing in northward and eastward by prevailing winds.