By Dr. Dara Stanley, University College Dublin
This blog is part of the ‘Dispatches from Researchers’ series, which features guest articles written by experts in pollination and related fields.
We know that pollinators are important. About 90% of all flowering plants have some kind of relationship with pollinators to help them reproduce. Our natural environment would be totally different without these precious insects.
Pollinators also play a crucial role in pollinating the food we eat. Estimates suggest that 75% of all crops we grow globally require pollinators in some way. This includes things like fruits, nuts, seeds, plants used to make oils, coffee, chocolate. Our diets would look very different if it weren’t for pollinators.
But what about closer to home? In Ireland, agriculture is dominated by animal production (mainly cows). Over 90% of our farmed land is grass used to feed cattle. In the past, these grasslands would have been diverse meadows used for both grazing and hay making. They would have been rich in native wildflowers and beneficial grasses, making them valuable habitats for pollinators. Today, most fields are dominated by perennial ryegrass swards, which is pollinated by wind. But some swards are also sown with clover, which is pollinated by bees, so we need pollinating insects to help produce these clover swards.
Oilseed Rape
The Irish tillage sector makes up 6% land area. Many tillage crops such as wheat, barley and oats are wind-pollinated, but for others, like oilseed rape, insects are more important.
In spring and early summer oilseed rape bursts into fields of yellow across the east and south of the country. It provides huge amounts of nectar and pollen and can be a very important resource for them at that time of year. On the flipside, oilseed rape is often treated with a variety of pesticides including fungicide and insecticide, so it can harm the insects it attracts by exposing them to chemicals.
During the Simbiosys project, we estimated that oilseed rape yields in Ireland were reduced about 30% when pollinators were excluded. This means that pollinators contribute about €3.9 million to oilseed rape production in Ireland per year.
With relatively open flowers, oilseed rape is accessible to a number of pollinators. Honeybees, hoverflies (especially drone hoverflies in the genus Eristalis), and bumblebees (especially the white tailed Bombus lucorum agg, and the red tailed Bombus lapidarius) are the most important pollinators of this crop.
Field Beans
Field beans are increasingly popular in the tillage sector and are mainly used for animal feed. As with other plants in the pea and bean family, they have complex flowers that are only accessible to some pollinators. During her PhD, Katie Burns found that without pollinators bean yield is reduced about 50%, meaning pollination contributes about €4,000,000 to bean production in Ireland each year.
Pollinators come in different shapes and sizes, and many have different length tongues. This means certain flowers are more accessible to some pollinators than others. Although honeybees and short-tongued bumblebees visit bean flowers, many make small holes in the back of the flowers and ‘rob’ nectar, which doesn’t result in pollination.
By far the most important pollinators of beans are wild bumblebees (responsible for 70% of the pollination), especially the long-tongued garden bumblebee (Bombus hortorum). We should encourage natural populations of this species wherever field beans are grown to maximise their production.
Strawberries and Apples
Fruits are also grown in Ireland, albeit in a smaller horticulture sector, which occupies 2% of the agricultural land area. Strawberries and other berries are very reliant on pollinators, but most strawberry pollination takes place in enclosed polytunnels with boxes of commercial bumblebees bought by growers. Apples, however, are grown outdoors in Armagh, and in the east and southeast, both for eating and cider production (there is a large Bulmers factory in Clonmel).
As part of her research, Katie also looked at the contribution of pollinators to apple production. She found that pollinators contributed 93% of the market value of eating apples (Jonagored variety) and 46% to cider apples (Dabinett variety). Apples had a wide range of pollinators contributing to their pollination, including honeybees, bumblebees, solitary bees and hoverflies. Honeybee visitation varied a lot between the cultivars, which suggests that relying only on honeybees for apple pollination might be a risky strategy. Solitary bees carried large amounts of apple pollen, and hoverflies visited flowers very frequently, and could both be good targets for orchard management to increase their numbers to boost pollination.
What does this mean for agriculture?
Interestingly, oilseed rape and bean growers rarely consider pollination during crop management. Sometimes honeybees are brought to the crops, but usually that is driven by an interest of the beekeeper rather than of the farmer. We found that pollination levels were mostly good in these crops, although there was some evidence to suggest that more pollination in spring oilseed rape could increase yield. This shows that for these crops we currently have stable enough populations of wild pollinators on farmland to do the job unnoticed, and this contrasts with many other parts of the world where supply of pollinators is big business. However, we must protect these naturally-occurring populations to sustain yield.
Irish apple growers more actively consider pollination, and often work with beekeepers to ensure availability of honeybees, use commercially available bumblebees, or actively manage orchards to benefit wild pollinators. This makes sense, as Katie’s work suggests that eating apple production could increase with better levels of insect pollination.
Irish agriculture might not rely heavily on insect pollination, but for some key crops such as clover, oilseed rape, beans, apples and berries it is vital. And that’s not to mention the importance for those who grow fruit and vegetables in their gardens and at smaller commercial scales. So next time you crunch into an apple, or take out your bottle of rapeseed oil, spare a thought for our pollinators!
Dr. Dara Stanley is a Lecturer in Applied Entomology in the School of Agriculture and Food Science, and Earth Institute at University College Dublin.
Find out more:
Burns, K.L.W. & Stanley, D.A. (2023) Irish faba beans (Fabales: Fabaceae) depend on wild bumblebee pollination for marketable yields. Agricultural and Forest Entomology, 25, 312-322.
Burns K.L.W., Stanley D.A. (2022) The importance and value of insect pollination to apples: A regional case study of key cultivars. Agriculture, Ecosystems & Environment 331:107911
Stanley D.A., Gunning, D., Stout J.C. (2013) Pollinators and pollination of oilseed rape crops in Ireland; an economic incentive for pollinator conservation in farmland. Journal of Insect Conservation.17, 1181-1189
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