Assessment On 1, 3-Dichloropropene And Dimethyl Disulfide As Soil Fumigants

Soil-borne diseases are a type of diseases that are caused by infection of pathogens in soil. The damages caused by soil-borne funi (Pythium ultimum, Phytophthora cactorum, Verticillium dahliae, etc.) and nematodes (Meloidogyne spp) become more and more serious after continuous crops cultivation for 3-5 years in general and cause severer impact on crop yield and quality. The yield loss caused may be 20%~40% generally, go up to 60% or even no harvest. With the rapid development of greenhouses and the high value crops in successive planting, soil-borne diseases become a predominant issue. The standard treatment for management of soil-borne pathogens, nematodes, and weeds in many high-value crop production systems has been preplant soil fumigation with methyl bromide (CH3Br; MB). However, MB is a substance of depleting ozone layer and listed as the controlled in the Montreal Protocol. It will be banned worldwide in 2015. Hence, the efficacious alternatives and alternativs technology has become one of the hotspot all over the world.The efficacy of 1,3-dichloropropene (1,3-D) and dimethyl disulfide (DMDS) as potential alternatives to methyl bromide to control nematode, soil-borne pathogens and weeds were evaluated in a laboratory dose–response study and field trials. The aim of the experiments were to assess the fesibility of 1,3-D and DMDS as alternatives to MB in China, promote the methyl bromide phasing out, and benefit Chinese growers.The laboratory dose–response study showed that the LD50 of 1,3-D to Meloidogyne spp. Fusarium spp. and Phytophthora spp. were 2.4309 mg/kg, 1.4058 mg/kg and 3.2753 mg/kg, respectively. The LD50 of DMDS to Meloidogyne spp., Fusarium spp., Digitaria sanguinalis (L.) Scop, Abutilon theophrasti Medicus were 5.3535 mg/kg, 3.7517 mg/kg, 10.1147 mg/kg and 17.1740 mg/kg, respectively. The results showed that 1,3-D and DMDS had good efficacy, as soil fumigants, in the control of nematode, soil-borne pathogens and weeds.The results of field trials showed that there were no significant differences between 1,3-D and DMDS applied by either shank injection or drip irrigation on nematodes and fungi in Qingdao, Qingzhou and Gu'an in 2006-2007. There were no significant differences between 1,3-D, at the dose of 16.8 g/m~2, or DMDS, at the dose of 80 g/m~2, and MB at the rate of 50 g/m~2 in control of nematodes and pathogenic fungi in soil. The treatments of 1,3-D and DMDS increased the yield of cucumber and tomato significantly compared to blank control. The field dosage of 1,3-D,16.8 g/m~2, and DMDS,80 g/m~2 are recommended. The results indicated that 1,3-D and DMDS can be used as potential alternative soil fumigants to methyl bromide for nematodes control in China.1,3-D soil column distribution experiments showed that 1,3-D could spread to 60 cm away from the application point in sandy soil. The effective range of 1,3-D to pathogenic microbes (Fusarium and nematodes) is between 15 and 20 cm from the application point in the soil. The volatilization study of 1,3-D showed that volatile rate of 1,3-D through plastic film with different specifications had great difference and the 1,3-D application concentration was highly related to the rate of volatilization losses.1.3-D capsule has good efficacyt on nematodes. 1,3-D and chloropicrin compound capsule has very good control efficacy on Meloidogyne spp., Fusarium spp. and Phytophthora spp.. 1,3-D has good efficacy on Meloidogyne spp. no matter it was applied as capsules or injection. The persistent period of 1,3-D capsules lasted for about six months in the fields.1,3-D plus chloropicrin in 2:1 volum ratio or DMDS plus chloropicrin in 1:1 volum ratio has good efficacy on soil-borne pathogenic fungi, root-knot nematodes and weeds.