Successful pollination depends on more than bumblebee activity alone. During hot summer conditions, both the behaviour of bumblebees and the temperature of the flowers can affect pollination and fruit set.
Pollination and flower temperature
Keeping pollination consistent
Consistently good pollination is essential for crop development and fruit quality. During the summer, however, maintaining consistent pollination can become a challenge.
When greenhouse temperatures rise above 30°C, pollination can start to slow down. As temperatures continue to increase, both pollination and fruit set can be affected. There are two important reasons for this.
Bumblebees need to keep cool too
During hot conditions, bumblebees need to spend more time cooling their nest. This leaves them with less time during the day to visit and pollinate flowers.
Keeping bumblebee hives as cool as possible can therefore help the colony remain active and leave more time for the bumblebees to do their valuable work in the crop.
Flower temperature matters
High temperatures also affect the flowers themselves. Unlike leaves, flowers do not benefit from the same cooling effect of evaporation. As a result, flower temperature can rise 5 to 10°C above the surrounding greenhouse temperature.
Under these conditions, pollen quality can deteriorate. This means that even when a bumblebee still visits and pollinates a flower, successful fruit set may not occur.
Monitoring greenhouse temperature alone therefore does not always tell the full story. Measuring plant and flower temperature can provide additional insight into the conditions surrounding pollination and help growers better understand why fruit set may be declining.
Creating better conditions for pollination
One way to improve conditions is to reduce the amount of heat entering the greenhouse. During summer, this can be done by applying a greenhouse coating or using a summer screen on hot and sunny days.
At the same time, monitoring plant and flower temperatures can help growers understand how well conditions support successful pollination. And last but not least, keeping bumblebees as cool as possible gives them more time to do their valuable work.
Successful pollination is therefore not only about having bumblebees in the greenhouse. It is about creating the right conditions for both the pollinators and the flowers.
Learn more about pollination in the online course How to achieve successful pollination.
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