ABSTRACT
The interactions between the various factors are so numerous that it is impossible to deal with every possible combination. The ever-changing environment resulting from the interactions of weather, site and farming system provides endless opportunities for the continued variation of pest, disease and weed populations. The ever-changing environment resulting from the interactions of weather, site and farming system provides endless opportunities for the continued variation of pest, disease and weed populations. If the climate and situation are particularly suited to certain commodities, then there is a sensible tendency for the production thereof to be concentrated in that area. This has a profound effect in two ways on the incidence and persistence of pests and diseases and the prevalence of weeds. Until efficient and reliable harvesting equipment is invented for commodities such as fruit, the farmer who cannot find harvest workers may be forced to change his cropping system.
