Managing Sclerotinia sclerotiorum (Lib.) de Bary in Sugar beet: One Pathogen, Three Diseases!!!

Sclerotinia sclerotiorum is an emerging pathogen of sugar beet (Beta vulgaris L.) where it causes leaf blight, seedling damping-off, and root necrosis. The continuous spread of this pathogen's damaging impact across sugar beet-producing states in the nation necessitates proactive management measures to reduce the risk of potential outbreaks. This study assessed inoculation methods and validated cross-infectivity with host crops grown in rotations, evaluated fungicide efficacy against seedlings damping-off, root necrosis, and Sclerotinia leaf blight. Trials were conducted twice using completely randomized designs. Reactions to treatments were measured as lesion sizes and by quantifying damping-off incidence. Results indicated that all S. sclerotiorum isolates can cause disease in sunflower, soybean, sugar beet or canola, independently of the crop they were originally isolated from. Sunflower and canola were the most susceptible crops. Crystal M837 cv. showed reduced susceptibility to leaf blight which seems to be the most common of the three diseases caused by S. sclerotiorum on sugar beet. Also, plant growth stage at the time of inoculation plays a significant role in sugar beet susceptibility to root infection. Fungicides Quadris, Proline and Priaxor reduced the severity of seedling damping-off, and root necrosis, but the latter two provided the most effective control of Sclerotinia leaf blight (P =0.05). This study gives a first look and offers vital information about fungicide efficacy, cross-infectivity, inoculation methods, leaf stages and varietal susceptibility to S. sclerotiorum in sugar beet, providing valuable insights in the development of an integrated fungicide management program for effective control of S. sclerotiorum, a potential threat to the sugar beet industry.