Defend Your Garden with Herbs

By Susan Belsinger and Tina Marie Wilcox

You’ve coddled your seedlings, nourished your soil, and provided a cozy habitat for beneficial birds and insects. Yet by early to midsummer, an explosion of aphids, Japanese beetles or some other insect pest threatens to destroy not only your serenity, but also your garden’s beauty and bounty.

The good news is you can stop these insect invaders without turning to dangerous pesticides. We rely on several common-sense strategies and time-tested herbal repellents that almost always do the trick.

Ant-Repellent Herb and Soap Spray

Garlic and Chile Insecticidal Soap Spray 

Keep Your Eyes Open

The strategies for staying ahead of garden pests are fairly simple. First and foremost, be aware of the life in your garden. Look for insects and mites and observe their activity daily, or as often as possible. Scout for common pests (click here for our "Garden Rogues Gallery"), but keep in mind that some insects, such as ladybugs, lacewings and praying mantises, are beneficial predators that can help control pests. If you have trouble identifying what you’re seeing, contact your County Extension agent, who can help. The Penn State IPM (Integrated Pest Management) Program for home gardens (http://paipm.cas.psu.edu/385.htm) has photos and information on 25 common garden pests.

Damaged leaves are a good indication that a plant is infested with some insect pest. If you look a bit closer, you’ll probably see eggs, larvae and/or adult insects. Check the bottom of leaves, where pests (especially spider mites) often congregate. Also examine stem junctions, where mealybugs hide their egg masses. Aphids are especially fond of the tender tips of plants, and ants even will carry them there to keep the population growing!

Spraying Simplified

Now that you’ve determined that a pest has taken up residence among your plants, you can take actions to stop it. Begin with the least toxic, least expensive and most convenient method first: a strong spray of water.

You’ll need an adjustable nozzle turned to the fan setting. This will allow you to direct a wedge of water over a large plant surface. Adjust the pressure so the water will wash away pests without damaging the plant. Spray the entire plant, side to side and top to bottom—as well as the top and bottom of leaves—until the plant is completely clean.

The best time to spray water (or any control product) is in the cool of the day when plants are not in direct sunlight. In direct sun, water droplets act as tiny magnifiers, concentrating light on plant tissues and causing them to burn.

Plant-feeding pests also are less energetic and easier to target in early morning and evening.

Besides using these water baths to stop pests, we also use a homemade garlic-chile-soap spray (click here for recipe), neem oil and horticultural oil, alternating among them monthly, if necessary, to keep pests off balance.

For instance, after we spot an infestation, we first blast the plant with plain water, then follow with garlic-chile-soap spray every three to five days until the pest is gone. A single spray rarely removes all of the tiny pest eggs, which are attached to leaves with strong webbing. Also, rain washes off the soap spray, so you need to re-spray every few days.

If the pest still is present after a month or so, we switch to a neem oil solution, applied according to package directions. And if neither the garlic-chile-soap nor the neem oil sprays do the trick after two months, we use horticultural oil spray the third month.

We find the following treatments very effective against most garden and greenhouse pests. Note: Whenever you try a new spray, be sure to test it on a small area and wait a day or two before you spray the entire plant.

  • Soap-based sprays. Soap sprays adhere to leaf surfaces and damage pest’s cell membranes. Several commercial brands are available. Or, make your own using biodegradable soap as the base: 1½ teaspoons of castile, Basic H™ or Murphy’s Oil Soap™ added to 1 quart of water, along with about 8 drops of insecticidal essential oils. (See left.) We also include soap in our Garlic and Chile Insecticidal Soap Spray (click here for recipe).
  • Neem oil. Derived from the neem tree (Azadirachta indica), neem oil kills, repels and interferes with pests’ ability to reproduce. It won’t harm mammals and is easy on beneficial insects. (Click here to see our "Herb to Know" about neem.)
  • Horticultural oils. These oils work by smothering pests. Use the refined "summer" types (also known as superior or verdant oils) to control soft-bodied insects during the growing season, when the temperature is below 90 degrees. Use heavier dormant oil on deciduous plants in winter.

Ant-Repellent Herb and Soap Spray

Garlic and Chile Insecticidal Soap Spray 

— Tina Marie Wilcox is head gardener and herbalist at the Ozark Folk Center in AR. Contributing Editor and herbalist Susan Belsinger lives in Brookeville, MD.

Sources for natural pest control products:  Arbico Organics, (800) 827-2847, www.Arbico-Organics.com; Gardens Alive!, (513) 354-1482, www.GardensAlive.com; Planet Natural, (800) 289-6656, www.PlanetNatural.com.