Assessment of the potential of a reduced dose of dimethyl disulfide plus metham sodium on soilborne pests and cucumber growth

Methyl bromide (MB), a dominant ozone-depleting substance, is scheduled to be completely phased out for soil fumigation by December 30th 2018, in China. The combined effects of dimethyl disulfide (DMDS) plus metham sodium (MNa) were assessed in controlling soilborne pests for soil fumigation. A study was designed in laboratory for the evaluation of the efficacy of DMDS + MNa to control major soilborne pests. At the same time, two trials were conducted in cucumber field located in Tongzhou (in 2012) and Shunyi (in 2013), respectively, in order to assess the potential of DMDS + MNa in controlling soilborne pests. Laboratory studies disclosed positive synergistic effects of almost all four used combinations on Meloidogyne spp., Fusarium spp., Phytophthora spp., Abutilon theophrasti and Digitaria sanguinalis. Field trials found that DMDS + MNa (30 + 21 g a. i. m(−2)), both at a 50% reduced dose, effectively suppressed Meloidogyne spp. with a low root galling index (2.1% and 11.7%), significantly reduced the levels of Phytophthora and Fusarium spp. with a low root disease index (7.5% and 15.8%), gave very high cucumber yields (6.75 kg m(−2) and 10.03 kg m(−2)), and increased income for cucumber growers with the highest economic benefits (20.91 ¥ m(−2) and 23.58 ¥ m(−2)). The combination treatment provided similar results as MB standard dose treatment (40 g a. i. m(−2)) or DMDS standard dose treatment (60 g a. i. m(−2)) in pest control and yield, but was more effective than MNa standard dose treatment (42 g a. i. m(−2)). Usage of all chemical treatments gave better significant results than the untreated group of control. Considering the economic benefits, the DMDS plus MNa combination (30 + 21 g a. i. m(−2)) could be used for soil fumigation in cucumber production in China.