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Gardening: Know when and how to use pesticides in your garden

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The Trident Technical College horticulture program pesticides class is online for the spring semester. Herbicides are compared, including organic products. Tony Bertauski/Provided

Did Santa stock your shed this Christmas? Perhaps a new shovel or shiny hand pruners? There are so many tools we can use to avoid using pesticides, but sometimes you have a decision to make. Like, do I get to eat the broccoli or are the cabbage loopers going to eat it all?

I would say one of the most important tools in the shed, if not the most important, is knowledge. Especially when it comes to pesticides.

The Trident Technical College horticulture program will be teaching an online pesticides class this spring. At the end of the semester, students are prepared to take the Commercial Applicator license exam. They are required to have a license to legally apply pesticides to a property that is not their own.

This class, however, isn’t about spray, spray, spray. It’s learning if you need to spray, what to spray and how to safely do it. What are the risks involved to you, the people around you and the environment? Which products are your safest options?

I’ve had many students say they don’t want to take the class because they don’t plan on using pesticides. I’m right with you. I don’t plan on using them, either. But when a cockroach crawls across my bed, we need to talk.

Integrated pest management is a plan that includes many options.

First, we can prevent pests with good gardening practices. This starts with cultural control. Adequate drainage prevents root rot. Quality soil ensures strong root systems. Correct fertilization stimulates healthy growth. Compost boosts your greatest ally, microorganisms.

Pests are inevitable. Insects want to live, too. That lush garden is a free salad bar.

Pests aren’t always a bad thing. There are many that don’t cause significant damage. Some, I’d argue, are even good to have in the garden. Take aphids, for instance. Aphids are the snack food of the insect world. Beneficial insects, such as lady beetles, parasitic wasps and assassin bugs, come from all around to feast on them. And when the aphids are gone, they start looking for other insects in your yard to eat. So when I see aphids, I say let them eat.

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Now, some people won’t agree. Aphids excrete honeydew, which gives rise to sooty mold. It’s harmless but makes plants look grayish-black. Not a good look. We can explain to the client that this condition is harmless, the insects aren’t damaging the plant and, in fact, they’re attracting beneficials. The client, however, might say they’re not paying for sooty plants. Get rid of the aphids.

What we’re talking about are thresholds. What is your tolerance for damage? Are you OK with it as long as it’s not harming your plants? My threshold for cockroaches in the house is about two or three a week. After that, we need to treat. My mother-in-law’s threshold is zero.

Once we’ve established a threshold and reached a point of unacceptable presence or damage, we determine a solution. This may be mechanical, such as flaming weeds. It might be physical, such as handpicking bagworms. It could be planting a resistant variety or pruning out the damage or amending the bed. Finally, it could be pesticides.

Residentially, I suggest products such as baits, soaps, oils or bacterial derivatives such as Bacillus thuringiensis or Spinosad. These are safer products for people, the environment and have little to no impact on beneficial insects. But they often require repeat applications.

Commercially, there are other products that require more knowledge to use safely. Improper usage risks contamination of aquatic organisms and groundwater, reduces microorganism activity in the soil, or results in residual toxicity to people and pets.

No matter what product you use, however, always read the label. It will tell you exactly how, where and when to use it as well as how to properly mix and dispose of leftover materials and empty containers. 

Tony Bertauski is a horticulture instructor at Trident Technical College. To give feedback, e-mail him at

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