Glyphosate Combined with Manganese Phosphite Reduces Charcoal Rot Severity in Soybean

Macrophomina phaseolina is the causal agent of charcoal rot in soybean and causes yield losses. Glyphosate herbicide can immobilize micronutrients like manganese and iron, thus heightening plant susceptibility to diseases. Phosphites (Phi) are elicitors which also act as fungicides and can potentially contribute nutrients. The effects of glyphosate (Gly), manganese phosphite (MnPhi), and their combination (Gly + MnPhi) on the in vitro growth of M. phaseolina mycelium and the severity of charcoal rot in glyphosate-resistant soybean plants. Results showed that MnPhi had the lowest mean IC50 at 288 ppm, while the Gly + MnPhi had the highest mean IC50 at 406 ppm. Gly + MnPhi showed a 31% reduction in charcoal rot severity in the roots compared to the untreated control. Since both active ingredients in Gly + MnPhi can translocate to the roots, this treatment holds potential in controlling charcoal root disease.