Is the soybean more susceptible to ASR in later reproductive stages?
The developmental stage has little to do with the susceptibility of the soybean to ASR; ASR can infect seedling-stage soybeans. However, ASR does not develop and sporulate as rapidly on soybeans in the vegetative stages as on soybeans in the reproductive stages. Therefore, fungicide application will not be cost effective and not be recommended until the soybean begins to bloom (R1). In 2005, ASR incidence and severity progressively increased as the crop aged.
