Stem borers in grain sorghum: II. Yield loss compensation in relation to borer attack

Abstract

The yields of Individual stems of grain sorghum In different categories of tillering and of injury by the stem borers Busseolafusca (Fuller) and Chilo partellus (Swinhoe) were obtained from nine plantings In each of three seasons. Tillering was stimulated by Insect damage, although the number of productive tillers did not differ significantly between insect-damaged and undamaged plants. Under favourable climatic conditions undamaged single-stemmed plants and the main culms of undamaged, tillering plants yielded the same, tiller yields being additive to main culm yields. Under sub-optimal climatic conditions the yield potential of undamaged plants decreased In relation to tillering potential, tillers being more adversely affected than main culms, and single stems being less affected than tillering plants. In damaged plants tillers and juvenile panicles contributed more to the total plant yield than in undamaged plants. Compensation of the main culms for loss of tillers through ‘dead heart’ and vice versa was dependent on the number of tillers produced.