Pests, diseases and weeds in groundnuts in Zimbabwe

Many of the weeds, pests, and diseases of groundnuts in Zimbabwe are problems in other groundnut growing areas in Southern Africa, but their relative importance obviously varies from country to country. The main weed problems in Zimbabwe are grasses such as "rapoko" and "shamva" and a few broad leaved species such as Commelina benghalensis and Nicandra physalodes. The weeds are controlled by preplant herbicide treatment and subsequent hand cultivation. A vast array of pests feed on groundnut foliage, the most conspicuous of which are leaf eaters such as loopers, semi-loopers, and bollworms. Routine insecticide sprays are necessary to keep the pests in check. More serious damage is done by a stem sap feeder, Hilda patruelis, which has proved difficult to control. Cercospora arachidicola and Phoma arachidicola are the main foliar diseases, and their interaction is discussed. Cercosporidium personatum and Puccinia arachidis are relatively minor pathogens affecting plants usually 3-4 weeks prior to harvest. Botrytis cinerea is a potentially serious disease but most of the commercial cultivars have a fair degree of resistance. Poor stands in communal areas make rosette an annual problem and sporadic outbreaks are seen even in well managed field trials. Aflatoxin levels are carefully monitored in all batches of groundnuts received by the Grain Marketing Board