The Organic Gardener's Guide to Pest Control

You don't have to use toxic chemicals or poisons to keep your garden free of pests.
by Mort Mather
June/July 1999
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Learn about ten alternatives to poison in a healthy garden.

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Once we decide to do an unnatural thing like turning the topsoil upside down and planting seeds that aren't native to this climate, we are sucked into providing more care for the garden. We have to control the area so that nature's garden doesn't overrun ours. We have to provide the soil with additional nutrients, since our method of planting and the plants we want to grow need different things than the soil cover nature would plant and provide for.

The ultimate control would be to dig a moat around the garden, fence it and enclose it entirely in an insect netting. But that won't keep out disease organisms that float on the wind or come in on shoes or clothing. I suppose it should be a plastic or glass-enclosed space with an air lock, where sterile clothing can be put on. That should work, but, of course, the space would have to be water and temperature controlled. And it still needs Oh, why go on. The more we try to control the growing conditions the more complex it gets and yet, inevitably, a disease organism or white fly or aphid or some other pest will get in. Much better, and far less expensive, is to try working with nature as closely as possible.

First, an attitude check. Don't think of the garden as a place where a wide variety of animals, miniscules and vegetables are lying in wait to attack your plantings. The vast majority of critters are beneficial. I'd even argue that everything I encounter in the garden is beneficial, including mosquitoes. It is important to remember this, lest you be tempted to spray something to kill an insect or bacterium that may be doing some damage to your crop. If you use a poison that kills on contact, you are killing hundreds of thousands of beneficial insects and microscopic organisms for every one of the critters you have identified as a problem. That said, let's begin.


Both knowing and spotting your culprits is the first step in any sensible method of pest control in the garden. The easiest and surest means of identification is to catch the pest in the act whether it be ground ivy creeping into the garden or a rabbit eating lettuce.

Animals can also be identified by footprints, manure, sometimes scent, fur and, finally, their habits. Insects are most often identified by what they eat, as most have favorite foods and do not eat indiscriminately. Some insects are very hard to see, whether due to camouflage, size or because they don't wait around to be seen. Some of them generate telltale manure. Others can be identified by the part of the plant they eat or the way they eat.

Miniscules, or microscopic organisms, are fungi, bacteria, viruses and nematodes. The work of these organisms can be seen in wilting, curling, mottled, discolored, spotted, blistered, white or powdered leaves; in lumpy, swelling, oozing or pinched stems; in fruit or flowers with spots, lumps, watery places or rot; and in plants that are stunted, dying or wilting.

If you've never gardened before, a list like that could cause your interest to wither. But rest assured it takes more than the mere presence of disease organisms to cause a plant to become diseased. Before anyone gives up on growing, consider that both o tax and I have peen gardening and writing about it for over 25 years and have never, to the best of my recollection, tried to combat a disease in the same season it was recognized. I don't recall ever losing a crop, though yield has been decreased at times.

I consider a disease in my garden much like a disease in my body. It will run its course, and I will try to be wiser and take better care of my body so I don't get caught again.

I hope you got my "animals, miniscules and vegetables" reference as a takeoff on the game 20 questions-"animal, mineral or vegetable?"because I'm going to bail out on vegetable pests after this paragraph. Let's face it, natural control of weeds is mechanical either through cultivation or smothering with a mulch. Most weeds do not need to be identified to be controlled naturally. You do need to know how they propagate, however. Bind weed and witch grass propagate through underground rhizomes and will come up through most mulch materials. To rid a field of these mechanically, it needs to be tilled several times at two-week intervals. This brings the rhizomes to the surface, where they will dry out and die. In a garden, you have the luxury (ha!) of chasing them by hand whenever and wherever they pop up until they are all gone. You need to know what they look like to do this. Weeds that propagate from seeds are best controlled by shallow cultivation every ten days in the spring and by keeping them from going to seed in the fall, or wide a mulch.


You will need a reference book to identify some pests. My favorite for many years has been The Gardener's Bug Book, 4th edition, by Cynthia Westcott (Doubleday, 1972). It has three features that make it wonderful. First in importance is actually the last chapter in the book, "Host plants and their pests." I may not be able to identify an insect, but I can surely identify the plant that is being damaged. Since most insects have favorite plants, this is the best place to start looking.

The bulk of the book is a listing of insects by type. I usually look up the plant first to find the most likely suspect, look up the suspect in the index, then turn to the description of the damage the insect does, its life cycle and how to control it. The controls are generally chemical, though not always. No matter, because the life cycle and description are what I'm most interested in. The third feature is color plates that help to find and identify the insect in the garden.

I have a half-dozen garden insect books that are newer, but Cynthia's is always my first choice. If you can't find a copy, look for a garden-insect reference book that is organized like it.

Once you can name the insect, any book describing controls will work fairly well. Of my more modern books, The Organic Gardener's Handbook of Natural Insect and Disease Control edited by Barbara W. Elks and Fern Marshall Bradley(Rodale Press, 1992) is my favorite for organization. It has the advantage over the Gardener's Bug Book in that it also covers disease and offers organic solutions.

Other gardeners are also good sources information. If they have been gardening in the area for a few years, they will probably be able to quickly identify your problem and, though their solutions may not be natural, may provide some useful insights. The Cooperative Extension Service, listed under U.S. Government in the phone book, can also be helpful.

Ask at a local garden store and you're likely to get a recommendation for a general purpose poison. "Here-spray this and it'll kill whatever's eating your plants." Yeah, it will. It'll also kill whatever's eating the whatever's eating your plants and millions of other innocent and helpful insects and miniscules. Your garden is not a good place for chemical warfare.


Once you know what pest you are dealing with, you can figure out how best to approach the problem. How does it get into the garden? Does it walk, fly, burrow, float on the wind, ride on your clothes? To use an expression from my youth: Was it horn, hatched or did it slowly accumulate in the garden? Will more follow? Will it multiply several times over the summer? How much damage is it likely to do? Will ignoring it this year be regretted next year?

But absolutely the most basic question is: "Does it need to be controlled?" Kind of silly to build a barrier or change the way you garden to control something that will pretty much go away if you ignore it. Even if an old timer who has been gardening in the same area for many years tells you an insect will devastate one of your crops, it doesn't mean it will. Your garden soil, your practices, your seed variety, the plants that are next to the one you are worrying about may all be different. Even the weather may be different. Plan a strategy for control if necessary, but use it on only part of the row and keep part for comparison.

For example, when cabbage leaves are being eaten and you have identified the culprit to be the cabbage worm, hand pick the worms that you can find. Do this for a few days just so you get an idea of how fast they are growing or how difficult they are to find. See if you can find some eggs, after looking in your reference book and learning that they are white, small and laid singularly on the underside of leaves. If you are worried the problem will get ahead of you, get an acceptable spray so you have it if needed. If real panic sets in, spray part of the row. No matter what happens to your crop, if you have been observant, you will have gained considerable knowledge for next year.


1.Make your plot a healthy haven.
Make your garden a heaven on earth where healthy plants resist disease and beneficial insects predominate.

The way to have a healthy plant is to make sure it gets the nutrients it needs in the proper amounts at the proper times. Sounds complicated, but nature will take care of the timing if we provide it with the raw materials. One of the most important materials is water. Will it rain at the proper intervals throughout the season? Not likely. Do we need to monitor rainfall closely and turn on the sprinkler anytime a week goes by without a significant rainfall? There are a number of reasons not to do that. A better solution is to turn the garden soil into a sponge that will soak up excess water during heavy rains and hold it in the root zone for plants to find when they need it.

You can also do your -part to ensure that the 18 or more elements plants need are available in the root zone for them to find. First, there is a basic difference between water soluble fertilizers and nonsoluble fertilizers. Chemical fertilizers are generally water soluble, though chemists have made some time-release fertilizers.

Fresh it manure is partially soluble The problem with water soluble fertilizers is that they are leached out of the soil in heavy rains. If the soil is sponge-like, less water will percolate through the soil and more of the soluble nutrients will be retained in the root zone.

Nonsoluble fertilizers are converted to a usable fertilizer over time. Some of them, such as rock phosphate, dissolve very slowly. Others, like the organic matter of manure and bedding, will be converted through the activity of microorganisms and insects. Nutrients in compost can be converted through a symbiotic relationship with roots. When the roots come into contact with the compost, they are able to absorb nutrients through cation exchange.

I am pretty close now to being in over my head, chemically. All we need to know is that if we put organic matter on our garden soil, it makes the soil feel nice, and nice soil does a pretty good job of keeping our plants healthy. Get the soil tested every few years and correct any imbalance as necessary.

2. Don't encourage pests to come into your garden.
I have attracted deer and skunks to the garden with seaweed. Spread in the spring, that fresh, salty taste brought in the herd. Seaweed has to be dug in right away or composted to avoid this problem. I also had some rotting seaweed that attracted flies. The flies laid eggs, which hatched into maggots. I used them under tomato seedlings. Bad plan. Though they were buried several inches down, a skunk was able to detect the maggots and dug up my tomato seedlings to reach the food it wanted.

Crows love corn and have great eyesight. Don't let them see you plant and don't leave any seeds exposed. This will only entice them to come looking for more.

Slugs mostly eat dead plant materials and they need a moist shelter during the day, which makes the environment under mulch perfect for them. I am pleased to have gotten my slug population under control, while still mulching more than half of my garden.

Unhealthy plants will attract insects to the garden. That may sound crazy but research has verified it.

3.Discourage pests from coming into your garden
If the pest is a mammal, it probably finds the garden strictly by chance. The odd deer, raccoon or groundhog is foraging for food, takes a taste and moves on. If the taste was to its liking and it didn't get sick, it will be back. A vigilant gardener will detect the animal quickly and make the second trip unpleasant.

One way to do this is to season the pest's favorite vegetables with hot sauce. Mix a tablespoon of liquid detergent and half a bottle of hot sauce in a watering can hill of water. Sprinkle this on the vegetables the animal has sampled and any others that are likely to attract attention. The detergent will help the hot sauce stick to the leaves. The plants need to be reseasoned after a rain. The hot sauce will discourage most animals returning for round two at your garden buffet. However, should you allow them more than one pleasant experience, they are likely to become more difficult to discourage.

Night foragers can be discouraged by lights, sounds and activity. When an old friend stopped gardening, he gave me a a homemade shielded light he'd constructed for keeping raccoons out of his corn. He had fashioned a cone around a 100-watt light bulb, lined the inside with foil and suspended it on a stake so it shone into his corn patch. He put a Christmas-light flasher in the line, so the bulb flashed a bright light into the rows. It worked for him for many years.

You've probably heard the one about the fellow who put his radio in the garden tuned to an all-night talk show. When he got up in the morning the radio was on an all-music station and the corn had been well picked over by raccoons.

The new motion detectors are interesting and probably more effective than the older methods. A woman I know rigged a garden sprinkler to come on whenever motion was detected. I can't remember how she did that, but she assured me that deer don't like surprise showers.

There are plants that some people feel deter insects. I remain somewhat skeptical, but I always plant green beans and potatoes side by side because supposedly the Colorado potato beetle shies away from green beans and the Mexican bean beetle is repelled by potatoes. I have no evidence to support this, but I plant them together anyway because I do think that larger patches of anything are probably not a good idea. The beans break up what would otherwise be the largest single crop in the garden.

Marigolds and nasturtiums are supposed to repel some insects, though we plant them in the garden more because they are pretty. Garlic is supposed to repel insects up to three feet away; there's no harm in planting it close to something that may be particularly susceptible to insect damage.

The best-known garden pest deterrent is the scarecrow. Inflatable snakes and plastic owls belong in the same category. I'm not sure any of these are very effective. I have found that once crows learn that pulled up corn seedlings will bring up a corn kernel, the best deterrent is deeper planting.

4.Put up barriers
The electric fence that I string around my garden-one strand at woodchuck nose height and one at deer nose height-works best if put up early to ensure an unpleasant first visit. Once the animal knows that there is a reason to get through, over or around the fence, the fence has to be better-lower, higher, arching outward, below ground. Below ground won't work for an electric fence, of course. If you are using a mesh fence, you need to know the size of the animals. Shrews and moles can get through a one inch mesh. A raccoon can climb over a mesh fence if it is strung too tightly. Leave a foot or so at the top unattached so it flops back on the climbing animal.

Slugs depend on moisture to get around. Dry areas are barriers to them. That is why I keep the grass short around the garden. I cultivate the lettuce and cabbage rather than using a mulch because the dry, dusty soil surface is very unappealing to them. Diatomaceous earth is a powder that will act as a barrier in wet weather when the dry soil does not. It is the calcareous remains of tiny sea animals that are sharp and cut the slugs.

One-inch netting will keep birds from eating berries. A fine mesh or gauze can be used to protect most plants from insects, since most get there on wing. I generally plant broccoli seed directly in the garden rather than in flats, mostly because I'm lazy and would rather have nature take care of light and moisture. Flea beetles frequently wipe out these plantings at the baby-seedling stage when there are just two small tender leaves. If the plants have the chance to get their first true leaves, they will grow vigorously enough to outgrow the beetles. A small piece of gauze held down with a few stones for the first few weeks of their life will do the trick.

After the year potato leafhoppers spread blight and drastically reduced my potato crop, I spread gauze (using some Remay that I had) over half the patch and tried to hold it down with boards. I left the other half of the potatoes uncovered to see if doing nothing would work as well as doing something (my usual approach). It did that particular year, but still, if I see leafhoppers, I will take some action. Barriers laid over rows of fairly mature plants are hard to keep in place because of the wind. I was also interested in what might be happening underneath the gauze. Were there potato beetle eggs hatching under there? To find out, I had to lift the covering.

5.Kill them
I have shot groundhogs. I don't do it easily, but there have been times when a groundhog has gotten too fond of the garden and too clever for me. To those who would chastise me for killing this animal, I say that if you let rodents run around in your home unmolested, you have earned the right to do so. I will add that catching an animal in a have-a-heart trap and transporting it away from family and friends to a most likely hostile environment may well be less humane than killing it.

I do not even kill insects without thought. Though when I find two adult Colorado potato beetles mating and dispense of them twixt finger and thumb, some may think me insensitive. My sensitivity is certainly dulled when I catch a critter of any size in my garden eating plants that I have planted and cared for. I don't go looking for them in other places, nor do I kill when there is a reasonable alternative.

There are three insects that I kill by hand fairly routinely. The Colorado potato beetle lays clusters of yellow eggs on the underside of the leaves of potato plants. By checking the plants every four to eight days and crushing the eggs, I can keep them from hatching into the grubs that do the majority of the eating. Cabbage worms and tomato hornworm's are the other two insects that I take the time to find when I see damage that I have come to know is theirs.

6.Poison only those that feed on your plants
Bacillus thuringiensis (BT) can be used on the same insects that I prefer to kill by handpicking. The Colorado potato beetle can he controlled with the strain BTSD and BTK, which will kill the larvae of any moths or butterflies that eat it. You don't have to worry that you will kill monarch butterfly larvae when you spray BT on tomatoes or cabbage because the monarch will not lay eggs on those plants. The monarch does, however, lay eggs on milkweed plants.

I keep both strains of BT in my refrigerator, but they are seldom used because I can usually keep ahead of the insects with handpicking. I guess handpicking would be a problem for someone who doesn't like to be in the garden. For me, it is something to do. It is almost like scratching your dog behind its ears when you pull back leaves and search for egg clusters or cabbage worms. Finding a tomato hornworm is akin to finding Waldo in a "Where's Waldo" picture.

Occasionally, I will feel the insects getting ahead of me though. This usually happens after several very hot, humid days when the insects hatch and grow faster, and I move more slowly. It might also follow a time when I have been too busy or away for a few days. It's then that it is helpful to have BT as a tool. It is a safe spray, as the bacteria is not at all toxic to humans, only affects very specific target insects and breaks down in the environment fairly quickly.

There is reason for not spraying it whenever the urge strikes, however. The more exposure insects have to it, the sooner they will develop a new strain of insect that will be resistant.

7.Use traps.
For animals, I find all traps to be lacking except mouse traps, which are effective but have to be set so no domestic animal will get hurt. Slugs can be trapped in a dish of beer, as they are attracted to fermenting liquids. They'll crawl in, and stay in, until they drown. Not all that appealing, a dish full of stale beer and slugs. Any moist, dark area where they can hide from the midday sun can be a trap for slugs. One time when my garden was overrun by them, I put down boards for my walkways. During the day I would turn the boards over and skate back and forth until I figured most of the slugs were dead. I wasn't gardening barefoot in those days.

Insect traps often use a stick), substance like the old-fashioned fly traps. Tangle foot can be spread around the trunk of a tree to trap insects that winter on the ground and crawl up the tree trunk. It can be spread on red spheres hung in apple trees to attract and trap flies that lay eggs in apples.

Flea beetles are attracted to yellow so yellow cards covered with Tangle foot will trap them, as will a yellow dish filled with water.

The electric zapper traps are likely to kill more beneficial insects than pests. Pheromone traps fool male insects into thinking they are about to find a suitable female. That just seems too cruel to me.

Any time you use a trap that attracts insects, you might consider placing it on the edge of the garden so that it attracts insects out of, rather than into, the garden.

8.Mobilize beneficial insects.
Lady beetles and praying mantis are the beneficial insects most often cited, probably because they are such voracious eaters of other insects. Praying mantis probably eat more beneficial insects than potential problem insects. Lady beetles eat their weight in aphids every day or some such incredible amount-good to have around if you have a lot of aphids.

If you have a lot of aphids, you also have an unhealthy garden and should get your soil tested and work on balancing the nutrients for next year.

There are many more beneficial insects. If you have a balanced environment in your garden, the insect populations will feed off each other as they were intended to do. I think it is a waste of money to import beneficial insects. If there is not enough for them to eat, they will fly away.

9. Plant resistant varieties
- If you find you have a problem with a particular disease, you might want to check the seed catalogs to see if there is a resistant variety. That is a purposely weak statement. Don't you want to select varieties first on how they taste and on their texture, not on how well they resist a disease? You may have a special problem like gardening in a foggy bottom or other environment that is particularly friendly to a disease organism. Barring that, I recommend you not use resistance as a guide. The following quote by P.R. Day, author of Pest Control Strategies for the Future Rodale Press, 1977), tells us why:

"If a parasite, as a result of a mutation, can avoid triggering the [artificially introduced] defense mechanism, its development will be unchecked . This is one reason why new mutant forms of pest and disease organisms appear which are no longer controlled by existing resistant varieties. [Dr. Reginald] Painter [a researcher in resistant varieties found

that, in time, these successful mutants may be able to replace the previously dominant bug or disease. While it's true that breeders can introduce other genes to bring about new resistant traits, the pest or disease will usually undo these defenses, too."

It takes ten years or longer to develop a new resistant variety, twice as long as it takes the insects to outsmart the plant breeders. With genetic splicing, scientists can bring on new varieties much more quickly. Also, and most bizarre, they are not limited to breeding plants with other plants of the same type. They aren't even limited to plants. They can splice genes from bacteria and other animal forms. Considering how fast nature is at circumventing changes like this, it seems quite likely that some of the mutations that combine our engineered mutations with nature's will bring about results that make our life more difficult rather than easier.

The U.S. Department of Agriculture, the Food and Drug Administration and the Environmental Protection Agency have all decided that we, as consumers and gardeners, do not need to know if our food or seeds have been genetically engineered. That means that we have to buy organically certified food and seeds from companies that clearly state that they do not sell genetically engineered products. A seed that is advertised as being resistant to an insect or disease might well have gotten that property through genetic engineering. We may not be unleashing a terrible genie into our environment, but this, at least, is certain: If it turns out badly, it is a genie that we will not be able to put back easily.

10.Poison indiscriminately
There are a number of naturally occurring substances that will kill most insects on contact. They do not hang around in the environment very long, which makes them preferable to chemical sprays, but I would consider it a failure if I had to use one. In 25 years of gardening on the same plot and five years of gardening commercially, I only used one of these once. It was the first time I planted cabbage. I had been told that cabbage worms would wipe out my crop, so when I saw cabbage worms, I panicked. I only sprayed half the crop and was happy to find that the unsprayed half did just fine.

For me these products - pyrethrin, rotenone and ryania being the most common - are an admission of failure. I won't use any of them for fear that they will throw off the balance in my garden. I also don't like to think about getting suited up in mask and goggles and gloves and washing all of my clothes or worrying about tracking something into the house. It just isn't the way I grow food.

The garden is a special place for me, providing so much more than healthy food. It is a partnership with nature. It is not a place to do battle or to be afraid. It is a place for contemplation, for solving puzzles, for creating and perhaps being created. It is a place where self-respect flourishes, as does the life that abounds.


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