|
|||||
|
|
Some Aspects of Chemical Control of Soil-borne Pathogens |
|
| Authors: | AFH Besemer |
| Institution: | Plant Protection Service, Wageningen (Netherlands) |
| Abstract: | The effect of a soil fumigant on soil-borne pests and pathogens depends largely on a sufficient distribution through the top soil and the availability of the fumigant or the biologically active degradation products in the water phase. Nearly all the fumigants are dispersed in the soil mainly in the vapour phase and therefore the amount of air between the soil particles is very important. Consequently on light soils it is relatively easy to obtain an efficient control, but on heavy or wet soils and on soil types with a high humus content it is rather difficult to get reliable results. The concentration of the fumigant in the upper few cm. of the soil is often insufficient to get good control after injection of the material at 15–20 cm. depth. The effect may be improved by using a plastic cover or a «split plot>> application. The elimination of most of the fumigant, to avoid a phytotoxic effect is a cause for concern on wet soils and on soil types with a high organic content. Factors influencing the decrease of the fumigant residue in the soil are discussed. The soil fumigant application gives rise to important changes in the whole ecosystem in the soil. Information on the influence on non-target organisms is scarce. The application of dichloropropene and of chloropicrin may lead to a noticeable effect on the nitrificating bacteria. The soil application of fumigants may give rise to residues in plants of the parent chemical or, to a larger extent, to residues of metabolites e.g. Br |
| Keywords: | |