Pollination strips could be worth up to £3.6 million to the UK courgette crop

An AHDB-funded PhD study has revealed the value of pollination services to courgettes, finding that pollination margins can improve bee species’ work, while also improving yields.

The study discovered that with pollinator insects like honey bees and buff-tailed bumblebees present, crop yields were 39% higher than when they were excluded.

That additional yield could have been worth £3.6 million to the 2017 courgette crop, with pollination services valued around £3,400/ha.

Results showed there was no significant difference in crop yield when humans pollinated each flower by hand compared to natural levels of pollination, showing how effective bees are with zero labour costs.

In courgette field margins, wildflowers were shown to attract bees into the crop, helping to provide stable long-term services across growers’ land.

It’s hoped the study will help growers to make informed planting decisions, which benefit both crop yield, bee population levels and the environment before the 2019-growing season begins.

The research was led by Dr. Jessica Knapp from the University of Exeter, who said: “We set out to develop a clear understanding of courgette pollinators’ behaviour and the crop’s requirement for pollination.

These findings could also relate to all crops within the cucurbit family, such as pumpkins, watermelon, and cucumber.

“Early season courgette crops flower when bumblebee foragers are most active, which boosts the number of pollinators in the crop. Bumblebees also loosely carry pollen grains on their bodies, aiding pollination as they make visits from flower-to-flower.

“Notably, wildflower field margins did not create a distraction to bees’ pollination work. They are an effective way of attracting pollinators into courgette fields and will help to conserve these important agricultural species.”

Courgette nectar and pollen measurements were taken to simulate bee population dynamics in ‘virtual landscapes’ with courgette fields present, using a bumblebee population model called ‘BEE-STEWARD’.

Pollination rates and the abundance and diversity of pollinators were measured across 23 different study sites with most based in Cornwall, and some in Worcestershire and Cambridgeshire.

The PhD research also showed:

  • Honeybees (Apis mellifera) and buff-tailed bumblebees (Bombus terrestris) are the most abundant pollinators of courgette;
  • Bumblebees showed a preference for courgette flowers in the morning, when flowers are open, before switching to flowers on the field margin in the afternoon when courgette flowers are closed;
  • Model simulations showed courgettes’ abundant nectar was able to improve bumblebee populations’, however, bees can only benefit from this transient nectar source if alternative floral resources, particularly pollen, are also available to fulfil bees’ nutritional requirements in space and time.

Bumblebees were found to be most abundant in fields with more wildflowers present. These fields also supported other pollinators like solitary bees which, whilst not key pollinators of courgettes, are key pollinators of other crops. This is important for mixed and rotational crop farms systems

The courgette value and planted area was taken from the 2017 Government horticulture statistics when 1,066ha of courgettes were planted.