Combinations of reduced rates of 1,3-dichloropropene and dazomet as a broad spectrum soil fumigation strategy in view of methyl bromide replacement.

Almost no single commercially available or registered compound is able to replace the broad spectrum activity of methyl bromide. However, combinations of for long known fumigants or their generators, showing good activity in the control of specific groups of soil borne diseases or pests, show interesting broad spectrum activity and even synergism. Well-known combinations are 1,3-dichloropropene (1,3-D) and chloropicrin, applied by injection or through irrigation lines. A few decades ago, combination products containing 1,3-D and methyl isothiocyanate (MITC) were developed and commercialized but were not Longer supported. As 1,3-D is an excellent nematicide with other target groups depending on contact time and tarping, and dazomet as a MITC generator shows fungicidal, nematicidal, insecticidal and herbicidal activities, studies with combinations of both were started again. Laboratory trials with different combinations of 1,3-D and Basamid (97 % dazomet) in soil columns showed interesting results both with Basamid solved in 1,3-D, although limited by temperature, and with simultaneously applied products, even at half dose of each, or even tess. In a further stage, small greenhouse trials were performed with tomato and lettuce crop and could confirm synergistic activity through the evaluation of crop stand and harvest results. Other trial work was performed in collaboration between Certis Europe branches and local research groups in both Italy and Spain. There again it was demonstrated that the combination of 1,3-D (injectable as well as emulsifiable formulations) with Basamid are able to control different phytosanitary problems in different crops. In parallel with the above mentioned trial work, emphasis is also made on careful and appropriate tarping of the soil, preferentially by improved gastight barrier film. The latter allows dose reduction as well as improvement of the fumigation performance. Barrier properties of commercially available fumigation film are now studied for both 1,3-D and MITC. Finally, it is emphasized that appropriate application systems and machinery need more attention to achieve good results with this type of fumigants, i.e. less volatile and with less good diffusion capacity as compared to methyl bromide.