Bumblebees overcome pollination challenges of outdoor crops

Pollinating outdoor crops, such as orchard fruits and blueberries, can be challenging for a host of reasons, says Biobest IPM and Pollination Specialist - Spiros Kavouras. Employing bumblebees, growers can upgrade production, boosting fruit set and size and therefore yields, while also benefiting from improvements in fruit quality.

Challenges to overcome

“Weather conditions can have a major impact on pollination levels,” says Spiros. “Rainy, cloudy and windy conditions can mean pollinators are unable to fly and effectively pollinate flowers. Crop flowering periods can be short – just 3-4 weeks – with the time flowers are receptive for pollination even shorter. It is critical to have sufficient pollinators to get the job done within this time frame.”

“In open field situations, there can be competition from other pollen sources, such as nearby crops or weeds that are more attractive to pollinators,” warns Spiros. “Some pollinators prioritise nectar producing flowers, which means crops such as pears receive few visits.”

Most popular commercially grown fruit trees - such as apples, pears, almonds, cherries, apricots and peaches - require cross pollination. For efficient fruit setting, pollen must be transferred from other cultivars. If too far apart, pollinators may not be able to travel between them impacting yield.

“For early blossoming crops, such as almond, apple and pear, natural pollinators can be scarce leading to poor pollination levels,” says Spiros. “This can also be attributed to pollinator population decline due to pesticide usage, species extinction and loss of natural habitats.”

Fruit quantity and quality improvements

“Bumblebees are widely employed in open field crops to increase % fruit set,” says Spiros. “Improving fruit numbers as well weight - as they bear more seeds – the bumblebees boost overall yield. They also deliver improvements in fruit shape, size and appeal while promoting a more even harvesting period – helping reduce harvesting costs.”

Super-efficient

Bumblebees are highly efficient pollinators as they keep working in the harsh weather conditions often found early spring. 

“Almond trees are usually the first to blossom followed by pear and then apple,” says Spiros. “With few pollinators active at this time of year, all three need bumblebees for efficient fruit set.”

“Bumblebees have a highly effective means of collecting pollen - ‘Buzz Pollination’ or sonication. Their rapid, vibrating motion dislodges large amounts of pollen from the flower.  With large furry bodies, they have more direct contact with flowers transferring a greater pollen load - this makes them super-efficient.”

“Compared to other pollinators, bumblebees require less time per flower and also work longer hours. With limited communication, they are less likely to migrate to other attractive crops and prefer to forage for pollen, so they can visit less attractive flowers. Producing minimal nectar, pear blossom is not attractive to honeybees, however bumblebees continue to forage for the pollen,” he says. 

Bumblebees boost cross-pollination rates as they visit all flowers in the target crop, flying between rows more randomly than honeybees, while also being able to fly longer distances.

“This is of great benefit to blueberries as cross-pollinated they produce larger, more even ripening fruits and higher yields,” says Spiros. “High-bush blueberries are self-pollinating, but the berries are smaller and slower to ripen.”

“Blueberries produce flowers with narrow corollas which bumblebees, with their long tongues, are well adapted to. The inverted flower – with the stigma far below the anthers – makes wind pollination challenging. However, the heavy, sticky pollen grains are ideally suited to buzz pollination which is why bumblebees achieve good fruit set.”

Specially designed hives

Biobest offers a range of solutions for the pollination of orchard fruit trees and blueberries.

“Our Multi-Hive is specially designed for outdoor use,” explains Spiros. “The three fully developed colonies are well insulated affording protection from the wind, rain and cold.  By maintaining heat, the workers exert less effort keeping the nest at the right temperature and exert more in to pollinating crops.” 

“For certain fruit crops we recommend Flying-Doctors^® Hives which contain our patented integrated dispenser system. This can combine reliable pollination with crop protection, with the bumblebees delivering specially formulated microbial pesticides while pollination.  Alternatively, the dispenser can be used with pre-collected pollen to boost pollination in fruit crops such as cherries, pears and kiwis.”