Controlling Plant Pests Naturally

Plant pests lurk: you've carefully prepared your soil, planted your garden, and watched your seedlings put on their first few leaves - when you suddenly notice your baby collard plants are starting to resemble green lace. There are little holes everywhere on the leaves, and hundreds of shiny dots crawling around! Oh no, some kind of insect pest! Now what?

(Answer to the riddle: flea beetles, spray them with diluted Alaska fish fertilizer)

Insect pests come in an overwhelming variety of sizes, shapes, and "MO's" - their own unique ways of eating your plants. Some plant pests chew holes in the leaves, some suck the sap from the stem, some nibble away at the roots or even crawl inside and parasitize the plant.

In chemical warfare, "one size fits all" - you just spray a poison that kills everything and "Voila!", you're done with it - except that:

  • What you spray on insect pests to poison them, you have also sprayed on the food you are going to eat yourself. (Would you sprinkle that stuff on your food at the dinner table?)
  • Most chemical insecticides kill everything, not just the "bad" bugs, severely disrupting the natural ecosystem
  • insects develop resistance to chemical poisons, which will create much worse problems in the future

So what else can you do to control plant pests?

A bad infestation of plant pests is an indication that things are out of balance in the vegetable garden. You can use an organic, naturally-derived insecticide such as neem oil to kill most of the pests in the short-term without causing any long-term problems, while at the same time working to bring overall health and pest-resistance to the garden ecosystem.

It's a little bit like taking Vitamin C and zinc when you're getting a cold: you take stuff to lessen the symptoms, but you also try to build up your immune system through healthful diet, enough sleep, and other good self-care measures.

In the garden, this would be:

  • Use of the appropriate natural insecticide for the insect you're dealing with
  • Increase the amount of compost you produce and use on your garden
  • Plant a flower "insectary" to attract and house beneficial insects
  • Purchase beneficial insects and release them in your garden
  • Use companion planting to confuse and deter harmful insects

My Favorite Natural Pest Controls

These won't work on every bug you may encounter, but they work on many - perhaps most - of them. For other, more specific controls, see link at the bottom. My standbys are:

  • good ol' soap spray
  • dilute fish fertilizer spray
  • dormant oil
  • neem oil

Soap spray works pretty well on soft-bodied insects such as aphids, and the fish emulsion works great on flea beetles, which seem to be very partial to my beloved collard greens. (I think it just smells so bad that they get nauseated and lose their appetite!)

I resort to either dormant oil or neem oil if the other remedies don't work. Dormant oil works by clogging the breathing passages of the insect and suffocating it, and neem oil works in a number of ways. You can buy both dormant and neem oils at garden centers, nurseries, and Home Depot.

Soap Spray

  • 1 bulb garlic
  • 1 onion
  • 1 Tablespoon cayenne powder
  • 1 Tablespoon liquid dish soap
  • 1 quart water

Whiz everything except the soap up in a blender, pour through a strainer and put in a spray bottle. Add the Tablespoon of soap and mix gently by tipping the bottle back and forth. Spray on affected plants. Watch carefully and spray as needed. Don't use antibacterial soap, and watch for any leaf damage. Some very strong dishsoaps can cause leaf damage. If you notice leaves turning brown the day after you spray, next time you spray, wait half an hour, then hose the soap spay off.

Fish Emulsion

Buy Alaska Fish Fertilizer from Home Depot, mix a tablespoon in a spray bottle of water, and spray on plants. Apply daily for a couple of days, and the flea beetles will go away. I think the fish emulsion just smells so bad they lose their appetites! (Thank you to the Botanical Interests Seed Catalog, where I learned this one. It really works!)

Common Plant Pests and Their Controls

The number of insects that can become problematic in the vegetable garden is overwhelming: aphids, flea beetles, cabbage moth and cutworm, Tomato hornworm, Colorado potato beetle, Mexican bean beetle, thrips, spider mites, whiteflies... where do I start? (Or, where will it end?!)

There are so many different kinds of insect pests that I would need an entire website to show them all, as well as how to control each one naturally. So I researched the web to find a website for my readers to use that has excellent photographs, descriptions and the appropriate natural control measures for each insect, and isn't trying to sell you anything.

Texas A&M University has such a site, which starts with photos of the insects grouped by whether they are chewing, sucking, or soil insects. When you click on any picture you're taken to a detail page on that insect, and if you click on the bottom of that link, up comes a list of controls, starting with the most environmentally friendly. The only downside to this site is that you need to click "More..." at the bottom of each control to see what it actually is. When you enter the site, just keep clicking through for more and more specific information. Thank you Texas A&M!

Texas A&M Vegetable Plant Pests Website

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