Epidemiology of Phomopsis Seed Decay of Soybean in Illinois

Abstract

Phomopsis spp. were recognized by a SHORTT, B. J., A. P. GRYBAUSKAS, F.D. TENNE, and J. B. SINCLAIR. 1981. Epidemiology characteristic thick, white coating of of Phomopsis seed decay of soybean in Illinois. Plant Disease 65:62-64. mycelium with or without typical Phomopsis pycnidia. Phomopsis is by far In a 3-yr study of seed decay of soybean (Glycine max) caused by Phomopsis spp. in Illinois, disease the predominant cause of soybean seed incidence was highest in 1977, lowest in 1976, and intermediate in 1975. A low positive correlation decay in Illinois and can be distinguished was found between temperature and disease incidence, but no consistent continuum of disease from from other seed inhabitants by the color, north to south within the state was apparent. The highest incidence of Phomopsis seed decay texture, and growth habits of the mycelial occurred along major waterways in the wet years of 1975 and 1977. A high positive correlation was mat. Other pathogens of soybean seeds found between disease incidence and rainfall during pod fill, indicating that moisture, rather than were infrequently observed. Therefore, temperature or geographic area, is the dominant environmental factor in disease development. we believe that the experimental erro Maturity dates of cultivars interacted with changing weather conditions to affect disease incidence. we b asi ng our t ifications error In our studies, cultivars in maturity group II had the highest level of Phomopsis seed decay. from basing our identifications on gross Cultivars used in seed production in Illinois should be grown at latitudes where they will mature late fungal morphology is very low. in the season and escape conditions conducive to high incidence of seed decay. The data were collected from 2,708, 2,713, and 2,699 seedlots harvested in 1975, 1976, and 1977, respectively, and Phomopsis seed decay of soybean seed decay of certified soybean seeds were analyzed with the Statistical (Glycine max (L.) Merr.) is part of a grown throughout Illinois in 1975-1977. Analysis System prepackaged computer disease complex caused by species of