The Truth About Pesticides
I’ve covered a lot of ground during my years as a garden educator. From hosting webinars about what plants you can grow to attract pollinators to writing blogs about the most appropriate watering practices for the California climate, my expertise and passion is rooted in eco-friendly gardening for one very important reason…
When sustainable gardening techniques and proper pest management practices are used, there is almost always no need for a pesticide.
Why is this? Even eco-friendly and DIY pesticides are harmful to beneficial predators and pollinators. All pesticides – even homemade – have risks and consequences. Although often unintended, the damage is still done. Beyond killing off the beneficials that promote a healthy garden environment, there are other issues with pesticide use that aren't discussed much.
The Problem With Pesticides
Pesticides can be complicated and hard to understand since information provided is limited and sometimes difficult to access. Plus, while it's always important to use a pesticide according to the label, they can be very challenging to read. The label has a lot of very important information that will help you understand how to best use the product, so it can cause unintended harm if misused – accidentally or not.
Questions to ask yourself when looking at pesticides: Is it clear what the pesticide does? How does it work? What is its mode of action? Is it a contact kill or does it need to be ingested? What is the pest and when is the best time to manage that pest (i.e., is it more effective to look at managing it during its larval phase)?
Sometimes it’s not even the pesticide itself that’s the problem, but the inactive components that are included to help the active ingredients work better. These might be the sticking agents, the surfactants, or the stabilizers. Also, certain pesticides may be more toxic in different environments – like if the chemicals enter local waterways during the rainy season. What’s the solution?
Are DIY, Eco-Friendly, and Synthetic Pesticides Safe?
For many gardeners with troublesome pests, the thought is that organic or eco-friendly pesticides are safer. They are… to an extent. These products have a lighter impact on the environment, which means that they break down with little to no lingering particles that pose a threat, impact, or pollute the environment (including the water).
However these pesticides – eco-friendly, homemade, or synthetic/chemical – are all designed to kill something, whether it’s an insect, a disease, a plant, or an animal. There are pesticides designed to repel and prevent or inhibit growth. Other pesticides have anti-feeding components and without knowing, by applying this to your garden environment, there are unintended consequences on the beneficial bees, butterflies, and birds.
Let’s dig into three examples of common pesticides and the potential risks you may not have thought about.
Bacillus thuringiensis (Bt)
Bt is commonly used to kill tomato hornworm, loopers on brassicas, and leaf rolling caterpillars on shrubs. Since a caterpillar's only job is to eat leaves from their host plant, the plant has evolved to be chewed on by caterpillars and will grow back in most cases. This might be alarming to you, but the plant will be fine. Also, these bugs are an important food source for birds. Even if you use a very narrow-spectrum Bacillus thuringiensis (Bt) that kills caterpillars by ingesting the pesticide, you pose a threat to the ecosystem at large, not just your garden.
Insecticidal soap
Sometimes a pesticide isn’t harmful to adult pests, but their larvae instead. Narrow spectrum insecticidal soap – either made from potassium salts of fatty acids or castile soap and water, not dish detergent– is applied to soft-bodied insects like aphids. Its mode of action is to disrupt the cell membranes of their exoskeleton, which cause the insect to dehydrate and die. This pesticide only kills soft-bodied insects, so beneficial adult ladybug beetles aren't impacted. But if the larva form is present, they’re killed.
Neem
If I had to guess, neem is the most popular pesticide by far. It’s known by name and has the reputation for being eco-friendly. I believe its popularity came after Rachel Carson‘s book “Silent Spring” was published in 1962 because neem may have been the only eco-friendly pesticide on the market. Maybe horticultural oil was too, but neem was the one that gained popularity. But despite being so well-loved, did you know that neem has growth inhibitors and anti-feeding properties?
That means that if parts of an invisible particle happen to drift when you’re applying it, the pesticide may land on the pollen and nectar parts of the flower. Then later a honey or native bee pays a visit to that flower. It brings pollen and nectar that’s contaminated with a growth inhibitor back to feed its brood. Butterflies can also have adverse effects if exposed to neem. It was found that hummingbirds who feed their young neem-exposed insects can cause growth and health issues in the young birds.
This impact on our environment and the wonderful being within it has been the driving inspiration for me to learn how to grow and manage gardens without (or very minimal) pesticides.
Tips for Using Pesticides
Now, I’m not here to shame anyone. There are rare occasions that I even use pesticides. That’s why I don’t shy away from talking about them, I just try to share more about their impact beyond the immediate intent to manage pests.
Currently, I’m using the bio-fungicide/bio-bacteriace Bacillus amyloliquefaciens for peach leaf curl, which is applied before the flowers have opened. I’ve been experimenting with it on black spot and rust on roses also because I want to talk about it with people when I am working in the pesticide aisle at garden centers. I have also experimented with different eco-herbicides in my gravel driveway to see what other gardeners might be dealing with so I can speak from experience with more confidence.
If you need to use a pesticides then there are some rules to follow:
Always choose eco-friendly pesticides
Use in accordance to the label
If the pest isn’t on the label, it’s not the correct pesticide
Always protect your skin, lungs, and eyes
Apply only to the pest, not to the entire area
Never apply to plants in bloom and avoid applying to the flowers or getting it on pollen or nectar so you don’t impact the beneficial pollinators
Apply at dusk when pollinators are not active
Never apply when a frost, a rain event, or a heat event is in the 48-hour forecast
Never apply to drought stressed plants; apply to plants that are properly hydrated
If releasing beneficial predators, give them time to do their job of eating the pests
Alternative actions to consider
An alternative action is to wipe the aphids off if there is no tolerance (however aphids are food for our beneficial predators). You can also attract more beneficial predators by planting insectary plants – grown specifically to improve biological pest control. My top picks are yarrow, cosmos, sweet alyssum, phacelia, asters, and California native buckwheat. You can also let popular herbs like parsley, cilantro, and dill go to flower.
Instead of reaching for a pesticide right off the bat, perhaps use water to blast the pests or just wipe them off with your fingers? You can also increase the health of your plants so that they can withstand small outbreaks and can grow through the pest problems.
Ways to Grow Together
It’s rare to need to use a pesticide. At a time when our precious wildlife is in danger, our environment is at risk, and many important insects, birds and animals are showing declines in their populations, less toxic alternatives are important to consider. Before you reach for a pesticide, dig into and treat the root of the pest problem first. If that fails, opt for organic or eco-friendly pesticides when possible. Your garden and the ecology surrounding it will thank you!