Combined use of chloropicrin (Pic) and 1,3-dicloropropene (1,3-D) is as effective as methyl bromide (MB) at controlling soilborne diseases in many trials and commercial uses. However, Pic and 1,3-D are both highly volatile and may pose strong exposure risks to humans and the environment. A gelatin capsule formulation containing Pic and 1,3-D has been developed to reduce exposure risks to workers and bystanders and improved application safety. We conducted two experiments in tomato and cucumber greenhouses located in Beijing and Qingdao, China, to study the efficacy of Pic plus 1,3-D gelatin capsules applied at different dosages and soil depths. Results indicated that both injection and gelatin capsules of Pic plus 1,3-D provided good control of soil nematodes and reduced disease index of Fusarium wilt and root-knot nematode. Plant yield of tomato and cucumber treated with gelatin capsules was similar to MB treatment. Based on our results, gelatin capsules applied at a soil depth of 15 cm provided better control of soilborne diseases and led to higher fruit yield compared to an application depth of 5 cm. In conclusion, a gelatin capsule of Pic plus 1,3-D is a promising and novel formulation, which not only shows good efficacy in controlling soilborne diseases, but also reduces potential exposure risks of fumigants.

    Sesquiterpenes in Eupatorium adenophorum are abundant in leaves and have great development potential as biopesticides. The toxicity of sesquiterpenes in immune cells and their corresponding immune functions are not fully understood. We evaluated the immunotoxicity of two cadinene sesquiterpenes 2-deoxo-2-(acetyloxy)-9-oxoageraphorone (DAOA) and 9-oxo-10,11-dehydro-agerophorone (ODA) by using histopathology and toxicology methods in vitro and in vivo in lymphocytes and natural killer cells in Kunming mice. The mice were given single doses of 75, 150 and 300 mg kg⁻¹ body weight (BW) of DAOA/ODA every day for a week. Serious damage to the thymus and spleen was found in tissue images with clear lysis reduction numbers and a loosened arrangement of splenocytes and thymocytes to the mice treated with 150–300 mg kg⁻¹ DAOA/ODA. Mice cytology was also affected with significant cellular alterations, increased splenocytes apoptosis rates (P<0.01), proliferation reduction (P<0.05) and natural killer cells activities reduction (P<0.05) when given 150–300 mg kg⁻¹ DAOA/ODA, the severities of which were dose-dependent. However, a 75 mg kg⁻¹ dose of DAOA/ODA showed no change in tissue or cytology after the 7 day treatment, and therefore was considered to be within acceptable safety parameters. Taken together, cadinene sesquiterpenes, as a type of toxic botanical component, have low environmental risks in small doses and should be further studied for their use as biopesticides.

The combination of 1,3-dichloropropene+dimethyl disulfide (1,3-D+DMDS), which forms a pre-plant soil fumigant, can provide a substitute for the environmentally unfriendly methyl bromide (MB). Three greenhouse trials were performed to evaluate the root-knot nematode and soilborne fungi control efficacy in the suburbs of Beijing in China in 2010-2014. Randomized blocks with three replicates were designed in each trial. The combination of 1,3-D+DMDS (10+30 g m−2) significantly controlled Meloidogyne incognita, effectively suppressed the infestation of Fusarium oxysporum and Phytophthora spp., and successfully provided high commercial fruit yields (equal to MB but higher than 1,3-D or DMDS). The fumigant soil treatments were significantly better than the untreated controls. These results indicate that 1,3-D+DMDS soil treatments can be applied by soil injection or chemigation as a promising MB alternative against soilborne pests in cucumber in China.