Efficacy, Residue Risk, and Soil Ecosystem Safety of Butylidenephthalide for the Control of Peanut Stem Rot

Peanut stem rot caused by <i>Sclerotium rolfsii</i> is becoming increasingly severe. Although butylidenephthalide exhibits great antifungal activity against <i>S. rolfsii</i>, its appropriate application strategy is unclear. Greenhouse experiments suggested that butylidenephthalide was suitable to be preventatively applied by root drenching at 400 mg/L for three times with an interval of 7 days. In field trials, butylidenephthalide exhibited an efficacy of 51.75% after 21 days and increased the peanut yields by 9.89%. Butylidenephthalide rapidly dissipated in soil and plants (<i>t</i>_1/2 = 2.28-3.41 d), with no residues detected in edible peanut kernels or haulms at harvest. Butylidenephthalide showed a strong uptake and accumulation ability in plants from the soil (root concentration factor/bioconcentration factor > 1) and a moderate upward conductivity from roots to the above-ground parts (TF_stem+leaf = 0.95). Butylidenephthalide exhibited low earthworm toxicity and stimulated bacterial/actinomycete populations while suppressing fungi in soil. Overall, butylidenephthalide showed a favorable efficacy, no residue risks, and high safety on the soil ecosystem in the control of peanut stem rot.