Almond orchards with more wild bees have higher fruit set – Klein et al. 2012

posted by Claire

Almond bloom has arrived in California. This provides a beautiful site for those driving through the Central Valley, but for the honey bees it means it is time to get working, with almond bloom being the biggest crop pollination event of the year. While honey bees are important for almond pollination, a team of researchers led by Alexandra Klein wanted to investigate (i) whether wild insects contribute to almond pollination and (ii) how the amount of “free” pollination provided by these insects vary with surrounding land cover. To explore this they observed the visitors to almond flowers in 23 orchards in northern California that varied in their amount of surrounding natural habitat. They also recorded the fruit set in those orchards as the percent of flowers producing almonds (calculated from a sample of branches in each orchard).

The Klein et al. (2012) study found that the ground nesting bee Andrena cerasifolii (Cockerell), sweat bees (particularly Lasioglossum species) and the bumble bee Bombus vosnesenskii (Radoszkowski) were the main wild insect visitors to almond flowers in the northern Californian orchards where they conducted their observations. They also found that orchards with more surrounding natural habitat had more visits to almond flowers by wild bees AND a higher percent fruit set. One reason for this might be that wild bees are flying in from the surrounding natural habitat to collect pollen and nectar from the orchards during the almond bloom. This study showed that almond orchards can receive “free” pollination service from wild bees which can supplement honey bee pollination and improve fruit set. This highlights the importance of conserving the remaining natural habitat around almond orchards.