Sunflower pollinators in Kenya: Does diversity influence seed yield?

Abstract

A field experiment was carried out in 2004 and 2005 to study diversity of sunflower ( Helianthus annuus L.) pollinators and their influence on seed yield in Makueni district, a semi - arid area in Eastern Kenya. The crop is prefered by the local community as one of the main sources of income. Farmers do not manage pollination i n any way for enhanced crop yield and hence they rely on feral pollination. Insect flower visitors were recorded and pollen was dusted in their body to aid in determining pollination efficiency index for each visitor. The influence of these flower visitors on the yield was assessed by comparing seed yield from plots that insects had access to and those to which they were denied access . In total , individuals of 6 Lepidopteran species , 5 Hymenopteran species , 2 Dipteran species and one coleopteran species wer e observed visiting sunflower floral heads. Apis mellifera L. was the most frequent visitor and had the highest pollination efficiency index . Plots which insect visitors had access produced on average 59% more seeds than plots which insect visitors were ex cluded. Presence of different species of visitors improved the crop yield, implying diversity is beneficial in pollination of sunflower