Does Invasive Plant Control Affect Pollinators?

You might think that removing plants of any type would negatively affect pollinators, as they would have less forage available, but that isn’t always the case. Controlling and removing invasive plants can actually benefit our native pollinators. Let’s talk about why that is!

Pollinators in B.C.

When we discuss pollinators, bees are often the first to come to mind. The Province of B.C. is home to over 450 bee species; other pollinators in our region include flies, wasps, butterflies, and hummingbirds. Some of our native bees are ‘specialists’, which means they rely on a specific group or species of plant for pollen.

Specialist bees or bee specialists?

For example, orchard mason bees (Osmia lignaria) are highly efficient and specialized pollinators of fruit trees like cherry, pear, and apple, and are often found in orchards for this reason. Similarly, some mining bee species specialize in dogwood pollen and depend heavily on native dogwood plants for food.

A male mason bee (photo credit: Stavros Markopoulos)

Because specialist pollinators have specific relationships with certain native plants, they are unlikely to forage on invasive species. When invasive plants spread and displace native vegetation, they reduce the availability of suitable forage for our pollinators.

Invasive plants don’t always make a good snack

Many invasive plants produce large numbers of flowers each season, which might lead you to believe that they offer abundant food for pollinators. While they can provide some nectar and pollen, this doesn’t necessarily mean they benefit pollinators overall.

Butterfly bush is not a good food source for pollinators

Take butterfly bush, for example. Despite its name, it is actually not a good food source for pollinators. While it does offer nectar to adult butterflies, it provides no habitat or food for their larvae. Since butterfly larvae cannot survive on butterfly bush, and the plant often outcompetes native species that do support the full butterfly life cycle, its presence can ultimately harm butterfly populations.

Better alternatives for invasive species

Instead of planting invasive species, which can be harmful to our native pollinators, consider some native or non-invasive alternatives instead.

ISCBC’s ‘Grow Me Instead’ guide is a great resource for finding beautiful alternatives that won’t harm the environment. As you click through a plant’s profile option, you’ll notice some are tagged as pollinator-friendly – these would be the perfect alternative for your garden!

Does using herbicides harm bees and other pollinators?

Herbicides are specifically designed to kill plants. The mode of action in herbicides is specific to plant enzymes and cells that are not found in animals or insects. In certain, very specific circumstances, it is one of the tools used by SSISC to control certain invasive plant infestations.

Out of an abundance of caution, SSISC takes extra precautions to minimize the risk of pollinators coming into contact with herbicide-treated plants. Whenever possible, herbicide applications are done in the early morning, when pollinator activity is typically lower. SSISC also prioritizes treating invasive plants before they flower. As Erin Galloway, SSISC’s Field Program Manager, explains, “not only is herbicide more effective at this stage, but flowerless plants are less attractive to pollinators.” She adds that “if the plants have already flowered, the flowerheads are clipped before treatment; this helps prevent seed spread and further reduces the risk of pollinators encountering treated plants.”

Bees are attracted to flowering plants and they are less likely to visit plants with clipped flowerheads.

What does the research say?

Research on the effects of pesticides on bees remains limited, often yielding conflicting results. For example, a meta-analysis on glyphosate and bees found that when used in recommended doses in agricultural settings, it might cause lethal effects. However, the study was later challenged with a letter to the editor, which pointed out some methodological concerns, prompting a response from the original authors. In their response, the authors state that the need for further studies is evident.

It’s also important to recognize that much of this research focuses on the European honeybee (Apis mellifera), a non-native species in B.C. Studies specifically examining native B.C. pollinators are even more scarce.

According to the Invasive Species Council of British Columbia, there is insufficient evidence that herbicides themselves are harmful to bee populations.

On the other hand, failing to manage invasive plants and allowing them to spread unchecked can have a significant impact on pollinators. As invasives displace native vegetation, they reduce the availability of high-quality forage that truly supports our environment—and our bees.

If you’re interested in learning more about this topic, we encourage you to explore the research for yourself. Diving into multiple sources and perspectives can help you better understand the complexities around pesticide use and pollinator health. The reference list below is a great jumping-off point.

Do you want to know how SSISC uses herbicides in the Sea to Sky region? Click here to learn more about our safety precautions and the regulations we follow.