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Introduction to “Pests” and their Prevention and Treatment

One of the hottest, most emotionally charged topics in the gardening world is the use of pesticides, the umbrella term for herbicides, insecticides, fungicides and the like (“cide” meaning “killing”). Washington Post writer Joel Lerner recently noted that there are now two camps on pesticides: “The chemically concerned, and those who can’t get the high-quality results they want because of the chemically concerned. Sometimes it’s neighbor against neighbor.”

Japanese Beetle
Japanese Beetle Damage

What About IPM?

Integrated Pest Management (IPM) — was developed with federal funding as a compromise or “balanced” approach to the use of pesticides and it’s become popular as an alternative to the “Nuke ‘em” tactics of the past.  It calls for lowest-impact methods to be used first and heavy-duty pesticides to be used only as a last resort. But does it go far enough? Many environmentally concerned gardeners assert (strongly) that NO potentially hazardous products should be used, period — because diseased and infested ornamental plants in the home garden can just be removed. No one’s livelihood is at stake; nor is feeding the nation. And I must say I lean toward that camp myself but I keep an open mind and offer here enough information for readers to make their own decisions.

Organics are Okay, Right?

Turns out, that’s not necessarily true. Some naturally occurring (organic) pesticides are actually worse than their artificial or synthetic competitors. Heresy? Well, guess what plant was a popular insecticide for decades? Tobacco leaves, with nicotine being the agent in charge of doing the killing, and killing it does. In fact, there are purveyors of “all-natural” home-remedies STILL encouraging gardeners to use nicotine to kill all the animal life in their gardens and here’s an article by an actual scientist dispelling those toxic old “solutions.” So “organic” products get really good press but the savvy sustainable gardener needs more information than that too-easy and potentially misleading label.

The Sustainable Gardener’s Philosophy

Do No Harm. Turns out Rachel Carson got it right — that pesticides have been unleashed on the unsuspecting public with inadequate information about the harm they may cause to humans, pets, local wildlife, and our water and air. The DDT she fought is no longer used but many products that are legal today are nonetheless dangerous (that’s why they’re “regulated” by the government). As a recent publication by Burpee’s puts it (and they’re no screaming alarmists): “The list of banned chemicals grows each year, a reminder that what we don’t know can hurt us.”

Tolerate Imperfection. Remember Joni Mitchell’s song “Paved Paradise” and the line: “Give me spots on my apples but leave me the birds and the bees”? Similarly, eco-gardeners are learning to accept a few chewed or yellow leaves, even the occasional dead plant. As the beloved garden writer Henry Mitchell said, “I do not grow anything that has to be sprayed.” Like having a Hummer in the driveway, vast expanses of ultra-green, weed-free lawns are fast becoming targets of criticism, leaving passersby wondering: “Hmm, wonder what kinds of poisons are needed to keep that garden that perfect.” Imperfection is IN. Wildlife-friendly gardening is IN. Safe and healthy lawns and gardens are IN.

Prevention is everything, so let’s get right to it.


It starts with putting the right plant in the right place. That means taking into account the right cold-hardiness, the right exposure to sun, and enough space. Sometimes it means choosing pest-resistant or pest-tolerant plants, or the most resistant varieties of a desired plant. This resistance can be innate to the species or the result of breeders selecting for that quality.

Create and maintain healthy soil, most importantly achieved by adding organic matter.

Mulch, mulch, mulch. In addition to its many other attributes, it keeps disease-carrying water from splashing onto plants.

Keep the garden clean by removing weeds and plant debris that could promote and shelter pests. Any diseased or badly infested plant parts should be removed as soon as you notice them (but not composted). Keeping tools clean can help prevent the spread of disease.

Attract beneficial insects, like ladybugs, and other critters (especially birds) by growing a diversity of plants in your garden. For example, achillea, dill and fennel all attract ladybugs; insect-eating birds are lured with suet. It also helps to include plants that are native to your region.

Avoid creating disease-promoting conditions. Don’t forget to water during drought periods (drought-stressed plants often succumb to problems even months later). Don’t water at night, especially if it involves getting the foliage wet. Don’t work among wet plants (disease can be spread that way.) Don’t overfeed. Don’t manhandle your plants, especially their roots.

Know your plants’ vulnerabilities and treat them accordingly.  This often means pruning and thinning to increase air circulation, as a way to prevent fungal diseases.

Keep an eye on your plants so you’ll notice problems soon. I recommend walking your garden and noticing every plant in it weekly (at least).

Slugs Hostaas
Slugs on Hosta

After a Problem Appears

First, the problem may be gardener-caused — you didn’t follow the prevention tips listed above. Been adding enough organic matter? Is your soil as good as it should be? Are your plants going dry while you’re at the beach? You might even try moving the plant to a different spot in your garden, though you might need to wait for the optimal time to do that, like autumn. These gardening solutions should always be the first to be used, long before chemical solutions, even the “organic” ones.

My favorite technique for diagnosing the problem is to Google the plant name and the word “pest” because the results will narrow the list of possibilities to a manageable one. Or take a small piece of the affected plant to a Master Gardener plant clinic or to an independent garden center. I once took a twig from a Pieris japonica to the horticulturist at a local nursery for help diagnosing its yellow, spotted foliage and overall lack of vigor. He told me to try treating it right for a year — with regular waterings and a little fertilizer — before even investigating the possibility of disease. Now that was great advice, which you’d never expect to hear from a garden center – they’re in business to sell products, after all.

Photo credits from top:  Japanese beetle damage, aphids, slug damage on hosta.

Stephanie Fleming was raised at Behnke’s Nurseries in Beltsville. Her Mom, Sonja, was one of Albert & Rose Behnke’s four children. She was weeding from the moment she could walk and hiding as soon as she was old enough to run, so many weeds, so little time. Although she quickly learned how to pull out a perennial and get taken off of weed pulling duty.

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