Answers to your gardening questions
effective Deer Fence!
A Few "Home-Brew" Insecticides
by Fred Davis, MG, Hill Gardens of Maine (To view other articles, click Archives)
Welcome through Fred's Garden Gate! Last time I cleared up a few gardening misunderstandings—myths, actually: (1) There are no plants which emit insect repellants on their own; (2) Earthworms are definitely not the destructive pests that some people think they are; and (3) It is clearly untrue that a person can't have a decent garden without frequently spraying powerful, chemical pesticides. This week, let's take a closer look at that last issue, and discover a few "home-brew" pesticides that are inexpensive, often surprisingly effective, and that won't poison our homes and gardens.
There are, in fact, a great many natural, less damaging and threatening—not to mention less expensive—alternatives for the control of bugs and plant diseases for both large and small stewards of the Earth. But before we list some of them, it's always wise to keep in mind that even a so-called "natural" or "botanical" (made from parts of certain plants) will kill or seriously hinder both harmful and beneficial insects. Pyrethrin, for example, which is made from processed Painted Daisies and which does a bang-up job of controlling just about anything from aphids to Japanese Beetles, will also do the same bang-up job of destroying large numbers of beneficial insects. Dragonflies, large ground beetles, ladybird beetles, lacewings, even wasps, hornets and bats can fall victim to this purported "safe" and natural insecticide.
Something else to consider: any substance powerful enough to kill bugs has the potential of inflicting measurable harm to household pets, garden wildlife, even humans—irrespective of physical or physiological condition. Always exercise reasonable caution while handling, mixing or applying any substance capable of affecting health or shortening human life.
First on our list is one that's referred to as the US Department of Agriculture Mix. It's nothing more than a mixture of two teaspoons of clear dishwashing detergent in one cup of practically any vegetable oil, which is shaken vigorously and then added to a quart of plain tap water. It can be used on virtually any plant for the control of soft-bodied, piercing/sucking insects like aphids or mealybugs. Apply as a spray every nine or ten days.
Next is one of my favorites: Alcohol/Detergent Spray. This one also has three components—a teaspoon of dishwashing detergent, a pint of rubbing alcohol (from the drugstore. . .not the drinking kind), and a quart of water. Be a little cautious here because the mixture might be too strong for tender houseplants like African Violets, orchids or tender, indoor leafy types. A thorough application to both upper and lower surfaces of leaves is best. The alcohol actually dissolves an insect's oftentimes rigid outer protective layer, allowing the soap to penetrate, suffocate and destroy. Good (actually "bad") for aphids, soft-bodied scale insects, whiteflies and mites.
One that I particularly like for the control of the ubiquitous slug is a mix of five parts of water and one part of household ammonia (non-sudsing is best). Ammonia is actually a source of nitrogen for most outdoor plants so, as you're destroying legions of slugs and get some of the spray on leaves, you're actually foliar-feeding the plant. This one is highly effective and kills on contact. You must actually get the spray on the slug, so the best time to spray is early on a moist morning or late on a damp evening when slugs are most active. A clever trick: temporarily spread several pieces of board here and there in the area late in the evening; then by the next afternoon (especially if it was a hot, bright day), numbers of the critters will have sought refuge under the boards. Turn the boards and spray the unsuspecting rascals!
I've used this last one for years: Wormwood, Garlic & Water. It's perfect for discouraging nibbling and
browsing furry creatures like woodchucks, deer and rabbits. Use your household blender set at very high speed. Pour in 2 cups of water, two
or three peeled and sliced cloves of garlic and a decent handful of wormwood leaves and tender growing tips (Artemesia absinthum -
the "wormwood" of the Old Testament), then turn your blender on until the mix is completely liquefied. Stay close to the switch
because the brew has a tendency to foam and may overflow if unattended (shades of "I Love Lucy"). Finally, either allow it
to completely settle-out for a few days and use the clear liquid part, or strain the mixture through several layers of cheesecloth, a coffee
filter, or a few layers of nylon hose.
You'll mix this "concentrate" one cup to one gallon of water, place in a sprayer of some sort, and spray the leaves of plants favored by browsing animals—hosta, daylilies, tulip buds. . .that sort of plant. A tip: if you just spray the tops of the leaves, the solution will wash off in the rain. So hit the undersides of leaves more thoroughly than the tops. You might try adding a tablespoon of Hot Pepper Wax to the mix for increased durability and effect.
There you have just a few. There are, of course, a great many more. One of the best of which is a 1/4-cup of Murphy's Oil Soap in a gallon of warm water for almost any small sucking insect. An easy spray.Give these a try. Leave the powerful toxic stuff with skulls 'n cross-bones on the shelf.
|Find your State and County Cooperative Extension Office||Which Maine Hardiness Zone Do I Live In? (.pdf)|
© 10/2007 Hill Gardens of Maine; 107 Route 3, Palermo, Maine 04354. All Rights Reserved. Updated: 08/07/11