Honey bees can help with better blueberry yield

Image by Pexels from Pixabay

Animal-mediated pollination is an essential ecosystem service on which over a third of the world’s agricultural crops depend. Blueberry fruit production is highly dependent on animal pollination and, although visited by a range of bee species in their native range and agricultural settings, bumble bees are thought to be their primary native pollinators.

Demand for blueberries has increased in recent years due to their perceived health benefits. Consequently, blueberry cultivation has expanded well beyond their native and original agricultural range, including several regions where bumble bees are not present. In South Africa, like many areas in the world, honey bees are the only commercially available pollinators for blueberries because many countries ban the importation of bumble bees.

Vegetables & Fruit talked to Keanu Martin about his recent study on why honey bees are important pollinators of South African blueberries despite their inability to sonicate, and Keanu’s ongoing work in the field. He is currently finishing his PhD at Stellenbosch University where he started his research on blueberries.

This study aimed to determine the benefits of honey bee pollination on blueberry fruit yield for the variety Ventura by comparing yields of honey bee-pollinated flowers to flowers where pollinators were excluded. The results showed that honey bees significantly increased berry mass by 72% and diameter by 31%. It was concluded that Ventura in South Africa can be pollinated by honey bees, and that honey bee pollination can be an effective substitute for bumble bees in areas where bumble bees are unavailable, such as South Africa.

Additionally, this study revealed that the pollination environment has a strong effect on the quality of fruit produced by the southern highbush blueberry variety Ventura. Moreover, all measures of fruit yield, were improved by the presence of honey bees and more so by hand pollination. In particular, yields are greatly increased (over 130%) by the addition of honey bees to areas where there are no pollinators. This shows that despite their inability to buzz-pollinate, honey bees do extract blueberry pollen from anthers and transfer it to stigmas. This was demonstrated by researchers in Oregon, USA who showed that honey bees in blueberry fields carry on average 1133 blueberry tetrads on their body, excluding their corbiculae. Honey bees were the only pollinators at the site and therefore the effects shown are a direct result of access to honey bees, rather than unaccounted wild pollinators. Thus, in areas lacking native blueberry pollinators, the addition of honey bees may significantly increase blueberry yields, translating into substantial financial gains. This provides valuable information for the pollination of commercial blueberries, particularly with respect to the underutilised role played by honey bees, and suggests some important directions for research on blueberry pollination.

The research showed that Ventura can produce fruit without pollinators. However, these fruits are of lower quality than the fruits of flowers exposed to honey bee pollinators. Selfpollination is not unique to Ventura, as other highbush blueberry varieties can also produce fruit in the absence of pollinators. However, these fruits also have a noticeably poorer yield compared to fruits produced by flowers with access to pollinators as found in other studies on highbush blueberries in North America.

“For the last year of my undergrad I was looking for a place where I could apply science, to actually add some value to a field, because I'm not interested in just doing science for the sake of science, I want my work to have real life applications in the world around me. I started looking at, blueberries, because I identified a gap in the research, especially for

South Africa in pollination around blueberries,” says Keanu. Once Keanu started working in the blueberry industry he found that research was sorely lacking and thus needed in the field. “I was one of the first people in South Africa to thoroughly look at the pollination side of blueberries from a scientific point of view. The important thing that I found was there was a direct application of my work. So, once I started seeing results and I started sharing it with industry, I could see that it had a direct influence on what was happening around on different farms,” says Keanu.

Of more value for Keanu was to see that his research was actually making a difference on the ground. One of his main objectives in his current research is seeing how producers can optimise the land that they have. To this end, Keanu started Keanu Martin Consulting to offer scientific-based solutions to the industry’s pollination problems. Keanu started looking at compatibility between different blueberry varieties. In the past, producers used to plant a single variety in a block. What Keanu now found was that generally, with all the varieties studied so far, a huge increase in yield followed as soon as blueberry varieties were cross-pollinated. Something else that is very interesting is that if you cross-pollinate with a different variety, it actually matters which variety you cross-pollinate with. Sometimes one variety is a lot better than another variety, although both will increase the yield. However, one undoubtedly wants to have the best combination of varieties – and that all depends on their compatibility with each other.

He also revealed that one of his current studies is observing the honey bees themselves. “I looked at how they move in an orchard. I've physically locked my eyes on a single honey bee, and then followed that bee’s flight pattern, which was extremely time consuming and difficult. But once you put in the time (about 200 hours), you start to pick it up their movements more easily.”

What he basically found was that the bees move predominately down a row instead of between rows. His final paper on the study will be released soon. This means that the study will have important implications for producers and how they plant the varieties in the future to make sure that they get the best cross-pollination.

“I am actually building a model to see how it works. This way I will be able to determine the best way to plant these varieties with the least amount of change, but resulting in increased yield because of cross-pollination,” says Keanu.

One of the biggest challenges Keanu experienced, was for a scientist in the industry to change people’s minds. Things have been done the same way for a long time, now research shows that there are a lot more things that we need to take into account.

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