Avoid all pesticides, herbicides, and fungicides in your pollinator garden.
Pesticides are designed to kill insects, and they do so indiscriminately. If you spray a plant to kill aphids, any other insect that is exposed to the spray or its lingering residue will also be killed. If you spray your lawn to kill grubs, the pesticides will also kill ground-nesting bees.
Even if a pesticide doesn’t immediately kill an insect, the poison will cause permanent damage. For example, bumblebee reproduction and nest behaviour is impaired with pesticide exposure. In my experience, most garden issues that are typically addressed with sprays and powders, can be effectively dealt with using natural means.
Also avoid herbicides and fungicides. Recent studies have showed that Glyphosate, a popular herbicide, harms honey bees navigation and gut bacteria (making them more susceptible to pathogens). Pollinators have enough problems already without adding others.
Pesticides may be more harmful for native bees
Since honeybees live in managed hives and can travel long distances to flowers, agricultural pesticides are usually sprayed when they have returned to their hives, or when their hives have been transported to another site altogether. Since many native bees live in the ground, and most live close to their floral resources, pesticides effect native bees more than honeybees. This Science Daily article “Pesticides influence ground-nesting bee development and longevity” summarizes these findings in a recent study.
Is that insect actually a problem?
I no longer automatically consider insects to be a pests in my garden. First, if I see an unfamiliar bug, I try to identify it. I’ve learned about lots of interesting insect visitors this way. Consult BugGuide, or Google a rough description, such as ‘red and black beetle on milkweed’. With a bit of research, I learned that the red and black beetle in my milkweed patch wasn’t destructive; it was actually a native Milkweed Beetle that eats the plentiful seeds of milkweed plants.
Most of the time when we’re concerned about bugs in the garden, it’s because they’re eating holes in plants. I actually welcome most plant-eating insects now because I know they play a crucial role in food webs. If it’s a caterpillar, it will either turn into a moth or butterfly, or become a protein-packed meal for a baby bird. The A Way to Garden Podcast has had several episodes about the important role insects play in our gardens, listed inWhat I learned about pollinators and other beneficial insects in 2018. Most of the time, holes in leaves indicates that you’re garden ecosystem is flourishing.
It is actually true that if you leave aphids alone, ladybugs and other predatory insects will take care of them. I was skeptical. When I saw aphids on my swamp milkweed plants, I left them on some of the plants, but squished them on others — just in case. Soon after, I saw various beneficial predatory insects showing up to eat the aphids. This problem solved itself. For more information about beneficial insects, listen to the Joe Gardener Podcast Predatory Beneficial Insects: Feared Foes of Garden Pests or check out Jessica Walliser’s book Attracting Beneficial Bugs to Your Garden from the Ottawa Public Library.
Some plant-eating insects are actually problems. The introduced Viburnum Leaf Beetle is defoliating and killing native viburnums. I have battled the larvae of this beetle on my highbush cranberry shrubs. So far, I’ve been able to control them by cutting off stems with egg casings in the fall, and squishing any larvae eating holes in the leaves in the spring. Japanese beetles are also a nuisance in my garden, but they don’t actually do fatal damage. Of course, here in Ottawa we’re all familiar with the destruction caused by Emeral Ash Borer.