The interest of apple orchard vegetation for the pollen supply of honey bees in South Tyrol (Italy)

Abstract

Fruit cultivation is one of the main economic sectors in South Tyrol (Italy) with one of the largest fruit production areas in the EU. In some parts of South Tyrol, more than 75% of the agricultural land is used for the cultivation of fruit trees, such as apples (Malus domestica). Almost 3500 beekeepers are managing 38 000 honey bee colonies, mainly in the valleys between 200 and 600 m a.s.l.. In this article, we aim to elucidate to what extent these fruit tree areas are visited and used by honey bees, especially outside the apple tree blossom period. We investigated the importance of apple orchards for the supply of pollen to honey bees during a period of five years (2016-2020), using palynological analyses of honey bee pollen pellets combined with vegetation surveys inside apple orchards. The results clearly indicate that the local apple orchards were the major pollen source for honey bees during the four weeks of apple tree blossom. However, in the weeks before the beginning of the apple blossom, and in the six weeks after, the apple orchards played a minor role in the supply of pollen to honey bees. Throughout the seasons investigated, flowers of a wide range of entomophilous and anemophilous plant species were the main sources of pollen. Broadleaved trees and shrubs contributed major parts of the pollen supply,whereas herbaceous plants, such as Veronica sp., Plantago lanceolata and Verbascum sp. were frequented far less by the honey bees. This suggests, that the honey bees may prefer pollen sources that provide large quantities of pollen, even though their flowers may not always produce nectar.