Combined use of 1,3-dichloropropene with dimethyl disulfide and chloropicrin for managing potato powdery scab and weed

Soilborne pests especially Spongospora subterranea f. sp. subterranea, which causes powdery scab, are posing serious threats to potato production in China. The combined impacts of 1,3-dichloropropene (1,3-D), chloropicrin (Pic) and dimethyl disulfide (DMDS) were assessed in controlling powdery scab and weeds for soil fumigation under field conditions. Two field trials found that 1,3-D + DMDS + Pic (1:3:2) at 30 g a.i. m^-2 effectively controlled Chenopodium glaucum and Digitaria sanguinalis with excellent control efficacy for plants and fresh weight (85.6-98.7%), considerably decreased disease prevalence and index of powdery scab with good control efficacy (86.9% and 86.5%), gave high yields (4.87 and 2.94 kg m^-2), and increased economic benefits (7.12 and 3.24 ¥ m^-2). The combined treatment yielded comparable results as Pic treatment in reducing disease index of powdery scab but was more effective than DZ treatment. Application of all soil fumigant treatments gave better results than the untreated plots in controlling weeds, reducing disease index of powdery scab, and increasing yields. This is the first report of soil fumigation for potato soilborne pests especially powdery scab control in China. Overall considering control efficacy, economic benefits and fumigant dose, the fumigant combination 1,3-D + DMDS + Pic could be utilized in integrated pest management programs of potato for controlling powdery scab and weeds in China.