An Assessment of Pest Damage on Grain Sorghum in Botswana

SUMMARY In trials conducted over five years, data on pest (insect, disease, bird) attack and yield of sorghum cultivar 65D were accumulated. A modified analytical method of damage assessment is described, which includes consideration of all pest occurrences and different levels and timing of pest attack. There was a positive correlation between crop yield and rainfall. The selective infestation of stronger plants, or the ability of those plants to support pest populations, is shown; thus, in most cases, yield reductions are masked. The importance of the tillering habit of 65D on yield, and its ability to compensate for pest damage by further tillering, are shown. A cultivar which does not normally tiller was tested in the final year. Effects on yield of all the pests encountered in the five years are discussed.