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Integrated Pest Management
by Liesbeth Leatherbarrow
by Liesbeth Leatherbarrow



Liesbeth has written for several western gardening publications, including Gardens West and The Gardener for the Prairies. She has also co-authored three gardening books: The Calgary Gardener (with the Calgary Horticultural Society), The Calgary Gardener, Volume Two: Beyond the Basics (with Lesley Reynolds), and 101 Best Plants for the Prairies (with Lesley Reynolds).


February 11, 2001

Increasingly, gardeners across the country are thinking twice before reaching for the pesticide or herbicide bottle to deal with an insect or weed problem. That's not to say that chemicals shouldn't be used at all - their careful, early and limited use helps to nip potential disasters in the bud, but consider the following. Both direct and indirect contact with garden chemicals is almost always injurious to a person's health; chemical residues found on many foods can be extremely harmful or fatal to chemically-sensitive people; liberal and indiscriminate use of pesticides kills beneficial bugs as well as the bad ones, and also the birds that feed upon them; and many pests have developed a resistance to the effects of certain chemicals, which makes their use worthless. So, if the use of chemical pest controls is to be discouraged, what can homeowners do to protect their garden investments of time and money from unwelcome visitors?
Integrated pest management (IPM) offers a solution to this dilemma. According to Jonathan Erickson, author of Gardening for a Greener Planet, IPM is "a biological control program that seeks to minimize the harmful effect of pests by keeping numbers below levels where they cause economic losses ... or severe damage to plants." To implement this plan successfully a person must first of all be familiar with the insects and diseases most likely to be present in their garden and which plants they are most likely to attack. This must be followed by taking some or all of the described biologic control measures. If a problem persists, despite a person's best efforts, then an appropriate synthetic chemical control must be selected and applied in a safe manner.

  1. KEEP A CLEAN GARDEN. Pick up and dispose of all garden debris - fallen leaves and fruit, stacked boards or rocks, sweepings, and cuttings. These provide potential hiding places and homes for pests. (It is true that a year-round organic mulch also provides cover for a variety of pests, slugs especially, but the benefits of mulch are so considerable that gardeners will have to decide whether they want to take the risk of pest infestations or not - perhaps a greater degree of vigilance for the first appearance of bugs and disease will help avoid disaster.) Leaves and fruit, especially those that are diseased, should be removed from plants and disposed of immediately. Conscientious sanitizing of pruning tools using a solution of one part bleach to ten parts water will also help prevent the spread of infection and disease.

  2. BENEFICIAL INSECTS. These insects protect plants from harmful insects by either attacking and devouring them (predators) or by laying their eggs in the pest and killing them when the larvae hatch (parasites). It is usually the larval stage of insects that does the most damage to plants, but this is also the stage that is most beneficial in killing "bad bugs." The adults and (or) larvae of ladybugs, lacewings, mealy bug destroyers, spined soldier bugs, and praying mantids are well-known predators of aphids, chinch bugs, white flies, and many other insects. Certain wasp larvae and nematodes are examples of beneficial parasites; the wasp larvae are effective controls for loopers, leaf rollers, hornworms, bagworms, webworms, and coddling moths, while the nematodes (tiny roundworms that live beneath the soil's surface) protect against root weevils, cabbage root maggots, beetle grubs, and other subterranean pests. Learn to identify these beneficial insects and their larvae and do not harm them. Beneficial insects can be bought in large quantities from some suppliers and released into the garden as a pest control measure, but remember that there are no guarantees they will stay in your yard. You also have a responsibility to these guests to keep them fed; this sometimes requires a supplementary feeding program.

  3. BENEFICIAL ORGANISMS. Garden pests have no inherent ability to ward off disease so by artificially increasing the levels of anti-pest bacteria already naturally present in the garden you can cause the pests themselves to become diseased without endangering the environment. Each type of such bacteria attacks the larvae of a specific bug, so a gardener can target individual bugs for control without harming beneficial insects or the birds that feed upon them. Bacillus thuringiensis (BT) is one such bacterium available commercially; several varieties of BT are effective against potatoe beetles, mosquitoes, corn borers, cabbage worms, tomato hornworms, gypsy moths, and blackflies. Another microorganism commercially available is Bacillus popilliae, or milky spore disease, which, once established, is an effective control for grubs (especially Japanese and Oriental beetles, and the rose chafer, which feed on grass roots).

  4. REPELLANT PLANTS. The smell and (or) taste of some plants can be offensive and repellant to some insects. Use such plants as a natural protection for other plants that are susceptible to these same insects. For example, spearmint and garlic repel aphids, so interplant them with aphid-susceptible plants such as lupins. Consult reference books for a complete list of repellant plants.

  5. CROP ROTATION. Some insect pests build up in the soil under the plants they love to infest, so by changing the location in the garden of a particular crop from year to year, the harmful effect of the pest can be minimized.

  6. HANDPICK VISIBLE PESTS. Pest that are big enough to see, and present in small enough numbers, can usually be removed from plants by hand. Slugs, caterpillars, weevils, beetles, and grubs can all be controlled in this way. Wear gloves or use tweezers for this task if you are the squeamish sort, placing them in a lidded container for disposal.

  7. BOTANICAL INSECTICIDES. Botanical insecticides are derived from roots, flowers, or leaves of plants. They break down quickly in sunlight and water (unlike synthetic chemicals) and are short-lived, both positive characteristics. On the negative side, they are generally "broad spectrum" and kill a number of insects, not just a specific one. Rotenone, pyrethrum, nicotine, ryania, and sabadilla are all botanic pesticides. They are sold under specific brand names so consult an expert at the local gardening center to help you select the appropriate product. Also be aware that some of the more recently developed synthetic chemicals are actually safer than their natural equivalents. So do your research when selecting a chemical, whether botanic or synthetic, and make the best decision for you, based on the advice from experts.

  8. SOAPS AND MINERALS. Non-detergent soaps, when used in conjunction with other control measures can be effective against aphids, spider mites, mealybugs, and whiteflies. Use a commercially available insecticidal soap, since common laundry or dish soap can damage some plants. Diatomaceous earth, a dust that is razor-sharp to soft-bodied pests such as aphids, slugs, and spider mites can be sprinkled on garden plants. It cuts their bodies as they attempt to cross it, which eventually results in dehydration and death of these pests.

  9. RESISTANT PLANT VARIETIES. Over the years botanists have successfully developed varieties of plants that are resistant to certain pests - mostly to diseases, but to some insects too. It is worthwhile spending some time researching which plant varieties are disease or pest resistant, and then choosing the resistant strains for your garden.





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