Visit path pattern of the honeybee {apis meullifera L. on the sunflower capitulum -correspondence with the location of seedless and incompletely developed fruits

Abstract

The occurrence of fruits with absent or poorly developed embryo, also defined as seedless or incompletely developed fruits (IDF), significantly reduces the sunflower yield. Failures in pollination, fertilization and physiological or morphological defects in the ovary and embryo, either post-pollination or post-fertilization genotype- and/or ambient-induced, are most common reasons for the development of this type of fruits. A detailed study of the visit path pattern of diurnal pollinators in the crop, mainly honeybees (Apls melllfera L.), showed that there was a significant negative correlation (r2=-0.61 : p < 0.05) between the areas covered by foraging paths (ACP), with the total IDF counted in the capltulum. Almost a complete limitation of Insect visitation (0-30% ACP) resulted in poor seed set and IDF percentage ranging from 10 to 17%. Partial limitation of the Insect visitation (60 to 90% ACP) diminished the number of IDF to 5 to 9%. Its is concluded that as much as 30% or more of the capltulum's area must be covered by bee visits to minimize the development of IDF.