A discussion on results of experiments carried out at the Coast Agricultural Research Station in Kenya on potato agronomy. High temperature is the major constraint in potato production at the Kenyan coast and hence development of agronomic (field) practices that will physically change the crop microclimate and increase yields are enhanced. Studies are being carried out on spacing, weeding, mulching, fertilizer application and intercropping of which mulching has already been found to improve the potato yield

The sweet potato weevils, Cylas spp., are the most destructive insect pests of sweet potato (Ipomoea batatas) in the world causing tuber yield losses of up to 90%. High costs and general non-availability of insecticides in Africa coupled with the concealed feeding behaviour of the weevils make it difficult to control these insects chemically. Previous studies have shown that improved agronomic practices such as early planting and harvesting and the use of deep-rooting sweet potato lines or earthing up the base of the plants of shallow-rooting lines (re-ridging) reduce weevil damage to sweet potato tubers. Sweet potato lines resistant to the weevils are also available in many parts of Africa. However, each control method used individually does not provide a satisfactory control. A low input control package being developed at the International Institute of Tropical Agriculture in Nigeria shows that the integration of the above-mentioned control techniques produces the best overall results. When two improved and resistant (TIS 2532 and TIS 70357) and one susceptible (TIBII) lines were planted late in the season and not re-ridged, as the farmers generally do, 42-58% of the tubers from the susceptible line were unmarketable due to weevil damage. Corresponding tuber losses were 5-17% for the two improved lines. Damage to tubers of early planted and harvested and re-ridged sweet potatoes was negligible.