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

Peanut stem rot caused by Sclerotium rolfsii is becoming increasingly severe. Although butylidenephthalide exhibits great antifungal activity against S. rolfsii, 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 (t_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.