Floral visitors, their frequency, activity rate and Index of Visitation Rate in the strawberry fields of Ribatejo, Portugal: selection of potential pollinators. Part 1

Abstract

This study was carried out in one of the most important strawberry (Fragaria × ananassa Duch.) pro- ducing regions of Portugal, the Ribatejo, and aims to describe the quantitative component of visits by strawber- ry floral visitors under open field conditions. The main objectives were: (1) to assess the flower-visiting insects of the strawberry crop; (2) to evaluate the percentage of frequency (F) and activity rate (AR) in order to deter- mine an Index of Visitation Rate (I VR ) for the different categories of visitors. This study allowed us to access the vast spectrum of flower-visiting insects of the strawberry crop and to characterize their visits regarding para- meters such as F and AR, used to calculate I VR . Based on the referred index it was possible to highlight three cat- egories of insect visitors: Syrphidae (Diptera), Apis mellifera L. (Hymenoptera) and native bees (Hymenoptera). Other aspects were evaluated such as no. ind/flower throughout three different phases of the blooming period and field conditions. All the parameters allowed us to gather a set of information inherent to each of these cate- gories, which will be useful for conservation and management procedures aiming at adequate pollination of the strawberry crop.