Least-Toxic Pesticides
Physical Controls
Not all pest control techniques require you to spray, sprinkle or pour! Physical control methods are a more direct way to either prevent pest problems from occurring or to get a minor infestation under control. These methods are usually very safe and environmentally-friendly, not to mention quite mentally satisfying to a pest-plagued gardener. There are many different techniques for physically managing pests, many specific to one pest species only, but here are a few basic categories to consider:
Traps – Some type of pests can be lured into traps. Traps commonly use food baits, colors, light, or reproductive hormones to entice pests. Ready-made traps for wasps, yellow jackets, whiteflies, and snails can be bought at many nurseries, or they can even be constructed at home.
Barriers – These types of controls are designed to physically prevent pests from reaching a potential infestation site. Like traps, barriers can be bought or easily made from materials around the home. Examples include seedling collars, window and patio screens, row covers, Tape and sticky barriers for crawling insects, protective clothing to cover skin, copper strip barriers for snails, covers for food containers and trash cans. These common sense controls may seem obvious, but they are often overlooked.
Hand-picking – While not effective against all types of pest problems, especially if the pests are overwhelming in number or small in size, some pests can be physically removed and destroyed. Examples include caterpillars, garden snails, fall webworms (by pruning), and fleas on pets (using flea combs). For those too squeamish to squash the pests, drop them in a bucket of soapy water and drown them. Snails and slugs should be crushed under foot or fed to ducks, chickens or other fowl.
Water Blasts – Slow-moving pests can be knocked off vegetation using a mist of high pressure water. Sufficiently harassed, they usually move along to more peaceful feeding grounds. Aphids and spider mites are especially easy to control using this method.
Natural Predators & Biocontrols
Using Nature’s system of checks and balances to keep insect pests under control is an effective and environmentally-safer way to manage pests in your lawn and garden. Introducing natural predators (beneficials) into your landscape is easy and fun. It can also be a great outdoor project for the kids. You can encourage beneficial insects to visit your yard by planting native plants (especially wildflowers) and providing a source of water. You can also purchase beneficial predators through mail order companies or at local garden centers. Here are some common beneficial insects you can purchase for your yard. Remember, some broadspectrum pesticides will kill beneficial insects, so switch to other types of controls or more selective alternatives.
Lady Beetles (Ladybugs) – This well- known garden predator is good for controlling aphids, mealybugs, soft scales, and spider mites. Normally seen in pictures and drawings as red and black, lady beetles actually come in many different color combinations. Lady beetles are probably the most commonly available beneficial insect. They have a tendency to wander so they may leave your yard for happier hunting grounds when they have taken care of your pest problem.
Lacewings – An excellent all-purpose garden predator, the adults and larvae of this insect feed on aphids, mealybugs, spider mites, the immature stages of thrips, and many other insects. The adults are bright green, delicate insects whose wings have a lacy appearance. Lacewing eggs are readily available through mail order gardening companies.
Praying Mantis – The praying mantis is a voracious predator of other insects, sometimes including other beneficials. Mantids usually have to be hatched from a chrysalis (a great project for the kids). Just be sure to spread the young mantids widely around your yard or they will eat each other!
Trichogramma Wasps – These are tiny parasites that attack the eggs of over 200 types of insect pests including the tomato hornworm, armyworm, cutworm, and webworm. They kill insects before they hatch and cause damage. Place the eggs in your yard during the springtime, and let the Trichogramma take care of those unsightly webworms that love to eat the leaves of your pecan trees.
Other Garden Predators – Avoid pesticide use and you will probably have these garden good-guys patrolling your yard: assassin bugs, minute pirate bugs, spined soldier bugs, paper wasps, ground beetles, spiders, hover flies, rove beetles, and predatory stinkbugs. Remember, birds, lizards, and toads also make great garden exterminators.
Other types of natural Biological controls are available to manage pests. Here are a few of the most common:
Bacillus thuringiensis (Bt) – This naturally-occurring bacteria can be used to control several different types of pests including certain caterpillars and fly, mosquito, and beetle larvae. There are several different varieties of Bt. Make sure you check to see that the variety you buy is effective against your pest problem. When ingested by a pest, this bacteria releases a crystalline protein that destroys the lining inside the pest’s gut. This causes the pest to stop feeding and eventually die. Animals and other beneficial insects are not harmed by the application of Bt.
Avermectins – These antibiotics (including ivermectin and abamectin) are produced by a naturally-occurring bacteria and can be used against an increasing variety of pests. Some are fairly toxic to mammals and aquatic life so they should be used with care. Avermectins also are available as a fire ant bait.
Beneficial Nematodes– Nematodes are microscopic worms that attack a wide range of soil-dwelling pest insects. These nematodes are not the same as the pest species that attack the roots of garden plants. The beneficial species can be bought commercially as pastes or powders and can be mixed with water for use in spray equipment or for pouring directly onto infested soil as a drench. Nematodes travel through the soil and kill susceptible insect species by penetrating their body cavity and infecting them with a toxic bacteria. Nematodes are vulnerable to drying-out and are therefore best applied during wet weather or at least after the sun has set.
Environmentally-friendly Alternatives: Botanical, Mineral, and Soap Insecticides
Mother Nature usually does a good job of balancing the pest populations in our yards. However, sometimes it is necessary to take action when a particular pest problem gets out of hand. Botanical, mineral, and soap insecticides are an acceptable option when preventative measures fail. Unlike most synthetic chemicals, natural insecticides are either harmless in the environment, or degrade quickly into less toxic substances. They also tend to be less harmful to beneficial insects than synthetic chemicals. However, natural insecticides should still be used sparingly, with extreme care, and only as the label directs.
Pyrethrum is one of the most widely used botanical (plant-derived) insecticides. Pyrethrum is a compound made from the dried blooms of the chrysanthemum plant. The active insecticidal ingredient is sometimes extracted from the flowers and it is called pyrethrin. Chemists have also been able to synthesize the active ingredient and the artificially-made compounds are call pyrethroids. Numerous types of pests can be controlled using these chemicals. Check the label on the products you select for a complete listing of pests controlled. Many pyrethrin and pyrethroid-based products have other chemicals added to enhance their effectiveness. Be aware, these additives may have health and environmental risks of their own.
Neem is a botanical insecticide that is extracted from the seeds of the neem tree which grows in parts of Africa and India. Native peoples have long been aware of the useful properties of this tree. It is the ingredient in many medicinal remedies. Neem is unique in that it has a triple action effect on pests. It acts as a repellent, growth regulator, and insect poison. It can be used to control a wide range of insects on ornamental plants and shrubs. Neem is also virtually harmless to beneficial insects like bees, lady beetles, and lacewings. Sometimes Neem products are advertised by the active ingredient, azadirachtin.
Insecticidal Soaps (Potassium Salt of Fatty Acids) are specially formulated soaps used for pest control. Their insect killing properties are the basis of the old home remedy of using a solution of dishwashing liquid and water to control pests. Scientists have discovered that Potassium salts of fatty acids, found in soaps, will penetrate an insect’s body and collapse cell walls. Companies have developed special soap products that contain a high proportion of these insect killing compounds. They are especially effective against soft-bodied insects such as aphids, mealybugs, and whiteflies. They also kill chiggers, fleas, mites, and ticks. Look for other pesticide soaps that kill weeds and certain types of garden fungus.
Horticultural Oil was once used only in the colder seasons when plants were dormant (an alternative name is dormant oil). Now, these oils have been improved to the point where they can be used, with care, in warm weather as well. Horticultural oil sprays will smother insects by blocking their breathing apparatus. Oils can also kill insect eggs by penetrating their outer covering and interfering with their development. These oils should be used carefully since you might inadvertently kill sensitive plants or beneficial insects.
Rotenone is another plant-derived insecticide that is isolated from several plant species, mostly from South America. Even though it is botanically produced in nature, the active ingredient is still a powerful toxin. Products containing it should be used with extreme care and only after the other safer, organic pesticides have been used. Rotenone is also highly toxic to fish, so do not use in areas that drain directly to a creek, river, lake, or other body of water.
Diatomaceous Earth (DE) is a powdery, white substance that is actually the fossilized remains of tiny microscopic algae. Diatomaceous Earth, or DE, sticks to pests and destroys their exoskeleton (the hard outer covering). It causes the affected pest to dry up and die. DE controls a wide range of pests but it can also be harmful to beneficial insects and spiders. An important thing to remember when using DE is to keep it dry. If it becomes moist, it doesn’t work as well. Also, be sure to buy the Diatomaceous Earth sold for pest control. The DE commonly used in swimming pool filters has been heat-treated and will not be effective against pests.