Almonds are one of the most economically valuable crops globally and require pollination by insects to optimise the production of high quality, marketable nuts. The Western honey bee (Apis mellifera L.) is an efficient pollinator of almond, and hives are often placed in almond orchards to provide pollination services.
While several studies have investigated pollen collection by honey bees, little is known about the usage of almond and other pollen sources by individual hives during almond bloom.
During almond flowering season, we fitted pollen traps over the entrance of 80 honey bee hives across three apiary sites in Victoria to better understand the collection of pollen by honey bees. We collected a total of 440 individual pollen tray samples during 21 days of data collection and identified 45,072 pollen grains.
We found that the weight of almond pollen collected by the bees followed the number of open almond flowers; that is, when there were more almond flowers (which in our study was at the beginning of the season), the quantity of almond pollen collected by the bees was also greater.
This suggests that the bees are responding to almond floral abundance over the course of a short flowering season and this tight relationship is very likely due to the large number of almond flowers being offered, much higher than any other resource around the beehives.
Honey bee collection of pollen other than almond?
From the 80 hives we worked with, only 17 hives collected almond pollen exclusively for the entire season. The other 63 hives also collected pollen from other plants (i.e. non-almond pollen).
Even though the collection of non-almond pollen was relatively low for most of these hives overall, the abundance of non-almond pollen found was higher in the early- and late-flowering stages of almond bloom. In other words, when bees were more active collecting almond pollen, they were also foraging for other resources to complement their diets.
Interestingly, we found some hives collecting more different plants than others. In total we found 18 pollen types (apart from almond) in our samples. One of the most collected plant species was dandelion, considered a weed in the study area, yet it is a significant pollen source for honey bees. There were several other native plants that were also regularly used as pollen source for bees, like acacias and eucalyptus.
A balanced and nutritional diet for honey bees can be supported through different types of pollen, which can result in greater colony strength and resistance against parasites. Even in a mass-flowering crop with great abundance of resources like almond, a diverse diet seems to be the norm for honey bees.
Given hives are often placed quite close together, we expected hives next to each other to contain similar pollen resources. However, we found the opposite! The distance among hives within the same apiary did not influence their pollen harvest. So, it is possible that other factors are influencing pollen collection over time.
Our study area was surrounded by a wildlife reserve and semi-natural vegetation, and the apiary sites were at similar distances from these areas. Therefore, more research is needed with a greater number of apiary sites at different distances to non-crop resources so we can better understand if this could potentially influence honey bee choice of pollen and how it would impact their performance pollinating almond orchards.
Understanding crop and non-crop pollen collection could inform honey bee diet needs and identify the plant species of importance to inform best practice bee management during almond flowering.
Honey bee hive placement for crop pollination should take into consideration the presence of non-crop vegetation surrounding the orchard as bees are using alternative floral resources. This may be an important factor to support honey bee diet needs and their performance as crop pollinating agents.
*Written by - Karen Cristine Bezerra da Silva Santos, Elizabeth Frost, Ulrika Samnegård, Manu E. Saunders and Romina Rader. The authors work across a range of different research and advisory roles. They are all broadly interested in pollination, landscape ecology and plant–animal interactions in natural and agricultural landscapes and work in conjunction with the Rader Lab group at the University of New England, Armidale.