Potato specialists at the University of North Dakato (NDSU) and the University of Minnesota recently published a bulletin in which they discuss several aspects related to the incidence and management of powdery scab of potatoes. According to Andrew Robinson, Neil Gudmestad and Francisco Bittara, the management of diseases caused by S. subterranea, the causal agent of powdery scab and root gall formation in potato, is difficult largely due to the nature of the pathogen. They recommend producers start with field selection and the adjustment of management practices. Planting clean seed into clean soil is a good beginning. Disease symptoms may increase or be exacerbated under waterlogged soil conditions and under excessive nitrogen levels. The amount of nitrogen also may increase the amount of inoculum returned by the pathogen to the soil. In addition, planting wheat prior to potatoes may increase the severity of symptoms.
In the U.S., fluazinam (Omega) is registered for the management of disease in roots and on tubers. Fluazinam applied in-furrow at planting may offer 20 to 40 percent disease suppression. Chloropicrin soil fumigation is effective at reducing S. subterranea inoculum in soil; however, it may exacerbate disease in roots and on tubers of susceptible cultivars. Read more