“Lately, there have been a lot of yellow jackets in our backyard, which has made our al fresco dining a challenge at times. What can we do to eliminate or reduce them? My garden is big with many different plants.”
– Laura Yee, Sea Villa
Yellow vest populations build up in the summer. They are considered beneficial insects, pollinating flowers and preying on maggots and beetles. This is the time to look more carefully for wasp nests in the garden.
Continue this vigilance until there has been a hard freeze that will kill the Yellow Vests. The yellow jackets are particularly active on warm, sunny days in late summer and autumn. You can see them flying in and out of the nest. Yellowjackets tend to nest in more secluded places, such as shrubs.
Wasps’ broad diet attracts them to urban areas because much of what we eat and throw away is food for them. They are particularly attracted to sweet things like soda and dessert. They prefer sugary foods and nectar from flowers, but will eat meat, trash, and picnic foods left outside. You’ll crawl into your soda can between sips if you’re not careful.
Wasps will continue to return to a location once they have found a good food source. So the best way to reduce this pest problem is to practice good hygiene in your dining area. There are traps you can buy for wasps, but since they use a pheromone to attract them, you may end up attracting even more of them into your dining area instead of controlling them. For best results, keep the area clean.
Just because they’re present during your mealtimes doesn’t necessarily mean there’s a nest in your yard. They will sting you aggressively if you disturb their nest with typical gardening chores such as planting, pruning, raking, and weeding. Vibrations from a mower next to or over a nest, or the impact of an unpredictable basketball can also disturb them enough to swarm and attack a nearby person. Their spines are smooth, meaning they can sting more than once, and the stings are painful.
However, there is no need to treat a nest unless it happens to be in an area that poses a hazard to pets or humans. Just avoid the nest when gardening. I currently have a nest under a periwinkle by the front steps to my house. I plan on leaving it alone as it’s easy to avoid.
Bald-faced hornets make large paper nests in trees and large shrubs at head height and above, so keep an eye out for them when you’re gardening, too. You are most likely to disturb them by pruning a tree or bumping into a nest with a piece of equipment. Paper wasps build nests under eaves, signs, benches and fence rails and will sting if disturbed. These are beneficial insects, so only control them if they pose a safety hazard.
If you find a nest that poses a danger to your family, your best bet is to use an aerosol insecticide formulated for wasps and bees to thoroughly drench the nest. You should be able to spray from afar to reduce the chance of getting stung. It is best to treat the nest at dusk when there are more wasps in the nest and they are less active. Stay away from the area for about a day as the treatment will upset her. Check the nest the next day and re-treat if necessary. Whenever possible I avoid killing a nest.
For more plant advice, contact the Plant Information Service at the Chicago Botanic Garden at [email protected]. Tim Johnson is Senior Director of Horticulture at the Chicago Botanic Garden.