Merissa Cullen - Biology - MU
One third of Ireland's 100 bee species are at threat of extinction due to habitat loss, and pesticide use, writes Merissa Cullen, PhD candidate in the Department of Biology

As spring rolls in with warmer weather and a grand ol' stretch in the evening, the only cloud for many are those pesky weeds in our gardens. No matter how much you mow, prune and pull, these weeds always seem to reappear. It’s much easier to head to the garden centre and purchase some weedkiller to get rid of the problem once and for all.
But you may not be aware of the negative consequences of herbicides for insect pollinators like bees who collect nectar and pollen from flowering plants. A sweet drink provided by plants, nectar provides bees with energy, while pollen is collected and brought back to the colony to feed young bees.

As bees collect pollen and nectar, some pollen gets transferred from flower to flower, fertilizing the plant. Whilst this is important for the reproduction of most wildflowers, it’s also important to produce food such as strawberries, apples, and tomatoes. 75% of crops benefit from animal pollination which is estimated to contribute $235-577 billion to the global economy each year.

But bees are in decline around the globe. One third of Ireland’s 100 bee species are at threat of extinction due to habitat loss and pesticide use in gardens, parks, and agriculture. The pesticides we use to get rid of unwanted plants such as weeds are called herbicides. Other pesticides used include insecticides (which target insects) and fungicides (which target fungal disease). In Ireland, herbicides accounted for 78% of the Irish pesticide market in 2020.

The most widely used pesticide in the world is the glyphosate weedkiller. Bees are exposed to glyphosate as it ends up in the pollen and nectar of weeds and nearby flowering plants after application. This can indirectly harm bees by getting rid of food sources such as dandelions and clover. Weeds that flower in early spring, such as dandelions, are especially important for early bumblebee queens waking up from hibernation who need to visit around 6,000 flowers a day to successfully start their new colony.

In theory, glyphosate shouldn’t harm bees directly, as it works by targeting a pathway only present in plants and some microbes. Whilst there is plenty of research showing the negative impacts of insecticides on bees, there is little research available on the effects of herbicides like glyphosate. Initial data shows it may not be as harmless as we’d like to believe, with negative effects reported for young developing bees and the beneficial microbes in bee guts, which are important for metabolism and immunity.

Despite the harmful impacts of some pesticides on insect pollinators, pesticides are seen as a necessity in modern agriculture to keep crops healthy and yield high. On the flip side, insect pollinators are necessary to pollinate many food crops, which also ensures a high yield. Without insect pollination, we would struggle to have a healthy balanced diet with the remaining food available to us, so it is important we do all we can to reduce negative impacts on bee health.

Scientists across Ireland are trying to solve this problem with the PROTECTS project by researching how pesticides used in Irish agriculture may impact insect pollinators. Once we understand this, we can come up with informed ways to limit the negative impacts of pesticide application whilst ensuring the continuing success of our agricultural sector.
When you consider that bees are dealing with contaminated food, habitat loss, and hunger, the stress could certainly be too much for these bees to handle. But it’s not all doom and gloom. There are various actions you can take to help pollinators in your own garden, balcony, or windowsill.

For many, the hum of the lawnmower is the backing track to spring and summer. But if you can embrace the wildflowers we consider weeds and refrain from mowing until mid-April, you will be providing lots of food for bee queens upon waking up from hibernation. You could also simply reduce the area you mow in your garden, leaving patches or strips of weeds for bees.

If you’d like to participate in a family-friendly project, making a solitary bee hotel will provide a place for developing solitary bees to hibernate. If you have a balcony, paved garden, or just a windowsill to spare – potted pollinator friendly plants such as lavender or grape hyacinths can provide much needed food for bees.

Finally, this one is obvious if you’ve read up to this point: ditch the pesticides! While we benefit from their use in modern agriculture, they’re not needed in our gardens and bees need all the food they can get to survive. If you really can’t stand wild flowering weeds, consider resorting to manual pulling, but remember that bees go where the weeds grow.

The PROTECTS project is funded by the Department of Agriculture, Food, and the Marine

This article first appeared in RTÉ Brainstorm
Photo courtesy of Jenna Lee on Unsplash