Chapter 17: Keeping Your Plants Healthy

In This Chapter

Controlling insect pests

Preventing plant diseases

Keeping animals out of bounds

Considering how tasty homegrown vegetables are, you shouldn't be too surprised to find that other creatures want to share in your harvest. And, no, I'm not talking about your neighbors. I'm talking about garden pests, insects that want to munch on your tomatoes, and animals, like deer, raccoons, and rabbits, that are just plain hungry. In addition, your plants face the threat of diseases, such as blight, which turns your potatoes to mush. With diseases, prevention is the key; once they take hold, they're almost impossible to eliminate.

Does the thought of all these potential problems make you want to run for cover? Well, you don't need to. It's true that insects, diseases, weeds, and animal pests can be very frustrating, but it's only really bad when the damage gets out of hand. The secret is to nurture a healthy, naturally balanced garden. Every garden can withstand some damage, and you have many weapons in your arsenal to prevent pest problems from getting out of control.

In this chapter, I tell you how to garden to prevent severe pest problems and how to identify the enemies. I also discuss safe ways to deal with these foes.

The Good, the Bad, and the Ugly: Controlling Pests

Most gardens are populated by a huge number of insects, most of which are neither good nor bad. They're just hanging out in your garden at no expense to your plants. But some insects are beneficial, waged in a constant battle with the bugs that are harming your plants. In the following sections, I describe both the good and the bad bugs and the safest methods of attack.

My approach to pest control is to have a maximum diversity of bugs in my garden. Despite what you may think, having some bad bugs around is important. Aphids are like hors d'oeuvres for some helpful insects, so it's okay to have a few in your garden. Otherwise, what will the good bugs eat? But accepting the bad bugs also means that you have to accept a little damage once in a while. So just try to manage the pests, not nuke them off the face of the earth. You want to keep them at acceptable levels without letting them get out of control.

In with the good bugs

As you know, some insects are beneficial to the success of your crops. Unfortunately, you won't always automatically attract these buggers to your plot, so sometimes you have to purchase them. Yes, that's right, you have to buy bugs. Following are some beneficial insects that you can buy inexpensively to help control pests that harm vegetables (see the appendix for companies that sell these beneficial insects):

Green lacewings: These beneficial insects are some of the most effective insects for garden use. Their voracious larvae feed on aphids, mites, thrips, and various insect eggs. Release them into your garden in late spring, after the danger of frost has passed.

Lady beetles: These insects are your basic ladybugs. Both the adults and the lizardlike larvae are especially good at feeding on small insects like aphids and mites. But releasing adults sometimes isn't very effective because Mother Nature has preprogrammed them to migrate down the road, so they leave your garden quickly.

Try preconditioned lady beetles, which have been deprogrammed (don't worry — the procedure is safe); they're more likely to stick around. Release lady beetles just before sundown; that way, they'll at least spend the night. Release a few thousand of them in spring as soon as you notice the first aphid.

Parasitic nematodes: These microscopic worms parasitize many types of soil-dwelling and burrowing insects, including cutworms and Japanese beetle grubs. Because grubs usually inhabit lawns, you have to apply these worms there, too, as well as around the bases of your plants. Mix the nematodes with water, and spray them on the soil around the bases of your plants in spring or fall.

Predatory mites: These types of mites feed on spider mites and other small pests. Add predatory mites to your garden in the spring as soon as the danger of frost has passed.

Trichogramma wasps: These tiny wasps (which are harmless to humans) attack moth eggs and butterfly larvae (that is, caterpillars). Release these garden good guys when air temperatures are above 72 degree Fahrenheit.

Good bugs are smart; they hang out in the gardens that offer the most diverse and reliable menu. That's why eliminating every last insect pest from your garden isn't a good idea. To get the good insects to stick around, follow these tips:

Avoid indiscriminately using broad-spectrum chemical or organic pesticides, which kill everything, the good bugs and the bad. If you do spray, use a spray that specifically targets the pest that you want to eliminate and that has minimal effect on beneficial insects; the label on the spray usually gives you this information. (I discuss safe sprays in detail later in this chapter.)

Plant a diverse garden with many kinds and sizes of plants, including flowers and herbs. Doing so gives the beneficials (beneficial insects) places to hide and reproduce. A garden with a variety of plants also can provide an alternative food source, because many beneficials like to eat pollen and flower nectar, too. Some plants that attract beneficials include Queen Anne's lace, parsley (especially if you let the flower develop), sweet alyssum, dill, fennel, and yarrow.

Provide a diverse habitat for beneficial insects. Have a small bird bath and evergreen and deciduous shrubs to hide in nearby. These elements provide water and shelter for beneficial insects, making it more likely they'll hang around to munch on some insect pests.

The bad-bug roundup

It helps to know your enemy, and insect pests command the largest army of invaders. The following sections list the most common insect pests that are likely to infest your vegetables as well as the best ways to control them. You can find control measures for the pests that prey primarily on specific vegetables in the individual descriptions of those vegetables in Part II; I also provide general points for tackling bad bugs in the later section "Methods of attack."

If you need more help identifying garden pests and other plant problems, contact a full-service garden center with a variety of reference books that you can look through as well as employees who have personal experience with local problems. Also check with botanical gardens, libraries, Web sites, or a local Cooperative Extension Service office. You should be able to find your county office listed under county offices (these services are usually managed by area land-grant universities) or under Cooperative Extension or Farm Advisor. Often a well-trained home gardener called a Master Gardener is available by phone or in person to answer your gardening questions. (Check the appendix for state Master Gardener contacts.)

Aphids

Aphids are tiny, pear-shaped pests that come in many colors, including black, green, and red (see Figure 17-1). They congregate on new growth and flower buds, sucking plant sap through their needlelike noses. Heavy infestations can cause distorted growth and may weaken your plants. Aphids leave behind a sticky sap that may turn black with sooty mold and may carry diseases, such as viruses, that infect your plants. Many vegetables can be infested with this pest, including cabbage, cucumbers, and broccoli.

Aphids are easy to control. A strong jet of water from a hose can knock them off sturdy plants (they rarely climb back onto the plant to feed), or you can use insecticidal soap or neem oil. Insecticidal soap also helps wash off the sooty mold. (I talk more about insecticidal soap and neem oil in the later section "Methods of attack.") But if you have only a few aphids, wait a week for beneficial insects, especially lady beetles, to move into your garden; they usually take matters into their own hands before serious damage occurs.

Caterpillars and worms

Caterpillars and worms, moth and butterfly larvae, are avid eaters and can cause a lot of damage to a variety of plants. Some are hairy caterpillars; others are smooth skinned and more wormlike. Caterpillars include tomato hornworms and cabbageworms (see Figure 17-2), which are described in Chapters 4 and 9 respectively. You can handpick caterpillars and worms to reduce numbers, or you can release trichogramma wasps. But the most effective way to get rid of them is to spray with biological controls, such as Bt or spinosad. (You can read more about Bt and spinosad in the later section "Methods of attack.")

Corn earworms

Corn earworms are a common pest wherever corn is grown. These 1 1/2-inch-long caterpillars with alternating light and dark stripes may be green, pink, or brown. In spring, night-flying moths lay yellow eggs on the undersides of leaves. The resulting first-generation caterpillars feed on the leaves. The eggs of later generations can be found on corn silks; the emerging caterpillars feed on the silks and the kernels at the tips of the corn ears, just inside the husks. The earworms, also called fruitworms, attack a variety of plants including tomatoes, beans, peas, peppers, potatoes, and squash.

The easiest way to deal with corn earworms on your corn plants is to just cut off the tip of the ear before you cook it. Or to prevent worms, you can spray Bt before the caterpillars enter the ears or fruit, but that doesn't always work. To prevent the worms from entering the ears, you also can place a few drops of mineral oil on the silks of each ear just as the silks wilt and start to turn from white or yellow to brown. (Don't do it too early or you'll interfere with pollination, but don't wait until the silks are all brown and shriveled either; you have about a week in which to work.)

Cutworms

Cutworms are 1/2-inch-long, grayish caterpillars. They emerge on spring and early summer nights to eat the stems of young seedlings, causing the seedlings to fall over like small timbers. Cutworms also climb up to older plants and feed on leaves and flowers.

To protect seedlings, surround their stems with barriers that prevent the cutworms from crawling close and feeding. These devices can be as simple as empty cardboard toilet paper rolls, Styrofoam cups with the bottoms cut out, or collars made from aluminum foil. Whatever you use, just make sure that the barriers encircle the stem completely and are set 1 inch deep in the soil. You also can trap cutworms by leaving boards around your garden; the worms hide under the boards during the day, enabling you to collect them. Parasitic nematodes also are effective against cutworms. (Flip to the earlier section "In with the good bugs" for more on these good pests.)

Flea beetles

Flea beetles are tiny 1/16-inch beetles that feed on vegetable leaves, riddling them with small holes. These beetles jump rapidly when disturbed, like fleas — hence their name. Various species feed on just about any plant in a garden, including eggplant, tomatoes, broccoli, cabbage, corn, potatoes, spinach, peppers, and sweet potatoes. Adult beetles can spread diseases — wilt in sweet corn, for example — and larvae feed on roots. Adults overwinter in the soil and on garden debris, emerging in early spring. Keep a close watch because these beetles can destroy young plants quickly.

To control flea beetles, make sure you clean up garden debris in the winter and till the soil. Use a floating row cover to exclude adults (I describe these covers later in this chapter), and release parasitic nematodes to attack the larvae. Pyrethrins and insecticidal soap also provide some control.

Japanese beetles

Japanese beetles can really be troublesome in many areas. These 1/2-inch-long beetles have coppery bodies and metallic green heads. They feed on the foliage of many vegetables, including corn, beans, and tomatoes.

Controlling Japanese beetles can be tough. Treating your lawn and garden soil with parasitic nematodes or with milky spore (a biological spray) may reduce the white C-shaped larvae, but more adults will probably fly in from your neighbor's yard. Floral-scented traps that attract adult beetles are available, but the traps may attract more beetles than you had before. If you try the traps, keep them at least 100 feet from your vegetables and encourage your neighbors to use them, too, to control the beetles community-wide.

Insecticidal soap and neem oil are effective against adult beetles. You also can handpick the beetles off your vegetables and stomp on them. Picking in early morning or evening is easiest because the beetles are sleepy then and tend not to fly away.

Nematodes

Nematodes are microscopic wormlike pests that can infect soil, especially in warm climates. They feed on the roots of plants and attack many vegetables, including carrots, tomatoes, and potatoes. Nematodes thrive in sandy, moist soil and can quickly stunt plants and cause roots to look hairy and knotted. Your best defense is to plant nematode-resistant varieties and to rotate your crops (see Chapter 16) to prevent a population from building.

These nematodes are different from the parasitic nematodes that I mention in the earlier section "In with the good bugs," which are actually beneficial for your garden.

Snails and slugs

Snails and slugs are soft-bodied mollusks that feed on tender leaves and flowers during the cool of night or during rainy weather. Snails have shells; slugs don't. Snails and slugs proliferate in damp areas, hiding under raised containers, boards, or garden debris.

To control these pests, roam through your garden at night with a flashlight and play pick-and-stomp, or trap them with saucers of beer, setting the rims at ground level. They'll jump in to drink the beer, not be able to climb out, and drown. What a way to go! Refill the saucers regularly. (These pests seem to like imported beers best, but why waste good beer on a slug?) Snails and slugs won't cross copper, so you can also surround raised beds or individual containers with a thin copper stripping, which is sold at most nurseries. In California, you can release decollate snails, which prey on pest snails; ask your Cooperative Extension Service office for information.

If all else fails, you can spread snail and slug bait containing iron phosphate. Sold as Sluggo and Escar-Go! this safe bait attracts and kills slugs and snails without being harmful to wildlife, pets, and kids.

Spider mites

Spider mites are tiny, spiderlike arachnids that you can barely see without a magnifying glass. If the population gets big enough, you can see their fine webbing beneath the leaves of your plants. As they suck a plant's juices, the leaves become yellowish with silvery stippling (small yellow dots on the leaves) or sheen. If things get really bad, the plant may start dropping leaves. Mites are most common in hot, dry summer climates and on plants with dusty (sooty) leaves. Tomatoes and beans are commonly infested.

A daily bath with a strong jet of water from a hose helps keep infestations down. You can control spider mites with insecticidal soap, which also helps clean off the plants' leaves. Applying summer oil or neem oil and releasing predatory mites also are effective.

Thrips

Thrips are almost-invisible troublemakers. They feed on leaves, giving them a stippled look and deforming them. You can distinguish thrips from spider mites by looking for the small fecal pellets that thrips leave behind. Thrips often pass on diseases as they feed. Beans, cabbage, onions, and eggplants are commonly infested. Many beneficials feed on thrips, especially lacewings. Insecticidal soaps and pyrethrins also are effective.

Whiteflies

Whiteflies look like small white gnats, but they suck plant juices and can proliferate in warm climates and greenhouses. They tend to congregate on the undersides of leaves, especially on tomatoes and beans. You can trap whiteflies with yellow sticky traps, which are sold in nurseries. In greenhouses, release Encarsia wasps, which prey on greenhouse whiteflies. Insecticidal soaps, summer oil, and neem oil are effective sprays.

Methods of attack

If the controls I mention in the previous sections aren't cutting it and you need to take further action, start with what I consider the first line of defense against pest outbreaks: physical barriers that keep the bugs away from your plants. The next step is to apply pesticides that are effective against a certain pest, are pretty safe to use, and have a mild impact on the rest of your garden's life-forms. In general, these products are short-lived after you use them in your garden — that's what makes them so good.

Physical controls

You can physically prevent pests from damaging your vegetables a number of ways. One of the best ways is to grab bugs by their tails, body slam them to the ground, and stomp on them. Handpicking, as it's usually called, works best with large bugs like tomato hornworms, Japanese beetles, snails, and slugs. The best time to handpick slugs is at night, using the light of a flashlight. If you have problems squashing bugs, drop them in a jar of soapy water instead.

Here are some other physical controls to try:

A strong jet of water often dislodges insects like aphids and spider mites from the leaves of vegetables, and they rarely climb back onto the plant. This method also keeps the foliage clean.

Barriers keep pests from reaching your vegetables. For example, place a small copper strip around the outside of raised beds or containers to keep snails from reaching your plants (snails won't cross the copper stripping). Floating row covers (see Figure 17-3), those lightweight, blanketlike materials described in more detail in Chapter 21, also keep pests away from plants. And if you have problems with cutworms, push a small cardboard collar (a paper cup with the bottom pushed out works well) into the ground around seedlings to keep bugs from reaching the stems.

Trapping pests before they reach your vegetables is another way to reduce problems. Trapping works best with night feeders — such as slugs and earwigs — that seek shelter during the day and are attracted to dark, moist environments. You can trap snails and slugs under a slightly raised board at night, and then dispose of the board in the morning. Earwigs will collect in rolled-up newspapers.

Safe pesticides

Here are my favorite safe spray methods of controlling harmful bugs:

Biological controls: Using biological controls involves pitting one living thing against another. Releasing beneficial insects (as I suggest earlier in this chapter) is one example of biological control, but you also can use bacteria that, while harmless to humans, makes insect pests very sick and eventually very dead. The most common and useful biological controls are forms of Bacillus thuringiensis, or Bt, which kill the larvae of moths and butterflies (that is, caterpillars). Another variety of Bt, B.t. tenebrionis or B.t. San Diego, kills the larvae of Colorado potato beetles. Bacillus popilliae (milky spore disease) is an effective control of Japanese beetle grubs.

Spinosad is a new biological control agent that has many uses. This soil-dwelling bacteria was discovered in Jamaica as a byproduct in the rum-making industry. It kills a broad range of insects, including caterpillars, thrips, spider mites, and leaf miners, but it isn't harmful to beneficial insects, animals, or pets. However, it is toxic to honey bees so spray it on cloudy days or late in the evening when the bees are less active. Like Bt, the insect must eat the toxin for it to work.

Botanical insecticides: Botanical insecticides are derived from plants. The most useful insecticides against vegetable pests are pyrethrins, which are derived from the painted daisy, Chrysanthemum cinerariifolium. They're broad-spectrum insecticides, which means they kill a wide range of insects. Unfortunately, that means some of the good guys are killed, too. So to avoid killing bees, for example, spray pyrethrins late in the evening. I usually use this pesticide as a last resort. The advantage to using pyrethrins is that it kills pests like aphids and beetles quickly, and has low toxicity to mammals. However, always follow the label and never apply more than is recommended.

The terminology can be confusing. Pyrethrum is the ground-up flower of this type of daisy. Pyrethrins are the insecticide components of the flower. You also may see insecticides called pyrethroids, however. Pyrethroids, such as permethrin and resmethrin, are synthetic compounds that resemble pyrethrins but are more toxic and persistent. They shouldn't be used in organic gardens. Consequently, I avoid pyrethroids.

Home remedies: Not all pesticides are exotic. Many gardeners have had great success using common household products to control insects in their gardens. One of my favorite home remedies is adding a clove or two of garlic and a few teaspoons of cayenne to a quart of water and then blending it all in a mixer. You then strain the solution to remove the chunks, and using a hand-held sprayer, spray your plants to control insects, such as aphids and whiteflies, and repel animals, such as rabbits and deer. Of course, after it rains, you have to reapply the mix. Commercial insecticide products, such as Hot Pepper Wax and Garlic Barrier, which are based on the common foods, also are available. Either type of product is effective, simple, safe, and fun to try.

Insecticidal soaps: Derived from the salts of fatty acids, insecticidal soaps kill mostly soft-bodied pests like aphids, spider mites, and whiteflies. They also can be effective against Japanese beetles. They work fast, break down quickly, and are nontoxic to humans. Insecticidal soaps are most effective when mixed with soft water because soaps can sometimes burn tender foliage.

Neem oil: Neem oil is extracted from the seed of the tropical neem tree. It has been used for centuries in India as an insecticide, to kill parasites in cattle, and even as a toothpaste for humans. Needless to say, it's very safe (except to unlucky pests). Home gardeners can purchase neem oil to repel and kill insects including aphids, whiteflies, leaf miners, caterpillars, and many others.

Summer or horticultural oil: When sprayed on a plant, this highly refined oil smothers insect pests and their eggs. The words "highly refined" mean that the sulfur and other components of the oil that damage the plant are removed. This oil is relatively nontoxic and short lived. Use it to control aphids, mites, thrips, and certain caterpillars.

Make sure that you don't confuse summer oil with dormant oil. Dormant oil should be applied to leafless trees and shrubs during the winter. It isn't meant to be used on vegetables.

Double-check the oil's product label to make sure that you can use the oil on plants during the growing season. Then follow the mixing instructions carefully. Water your plants before and after applying the oil. But don't apply the oil if temperatures are likely to rise above 85 degrees Fahrenheit. When it's that hot, the oil can damage plant leaves.

Even organic pesticides that have relatively low impact on your garden environment can be dangerous to use as well as toxic to humans; this is true of several commonly used botanical insecticides, such as pyrethrin and rotenone. Rotenone is a botanical pesticide that was used heavily in the early days of organic growing, but now has lost favor with many gardeners because of research showing a potential link to cancer and Parkinson's disease. I don't recommend it.

Always follow the instructions on the product label exactly; in fact, not following these instructions is against the law. Also, wear gloves when mixing and spraying pesticides, and spray when the wind is calm. Store the chemicals in properly labeled containers well out of the reach of children (a locked cabinet is best). Dispose of empty containers as described on the label, or contact your local waste disposal company for appropriate disposal sites.

Gardening to Eliminate Diseases

Diseases differ from insects in that, with bugs, you can take action after you see them. With diseases, once you see symptoms, it's often difficult to stop the diseases from spreading. However, you can prevent or at least reduce most vegetable diseases by using good growing practices or by planting resistant varieties. Most vegetables have some varieties with disease resistance; see the chapters on individual vegetables in Part II for details. In the following sections, I provide useful methods for preventing and handling some common diseases.

Avoiding diseases with good habits

Here are some cultural practices that can help you avoid plant diseases:

Remove infected plants. After you've identified a plant with a severe disease problem, yank out the entire plant. Even picking off infected leaves helps prevent a disease from spreading.

Avoid overhead watering. Overhead watering can encourage foliage disease organisms to prosper. If you can't avoid this watering method, at least water early in the morning so plants have a chance to dry out before nightfall. Using drip irrigation or watering in furrows helps keep foliage dry (see Chapter 15).

Space plants properly. Planting vegetables too close together reduces air circulation between them, a condition that favors disease and allows diseases to spread from plant to plant more readily. Keep your eyes open for developing problems.

Keep your garden clean and tidy. Many diseases spread on plant debris, so rake up fallen leaves and remove dead plants. Also, keep the spaces under any containers clean. Removing diseased leaves can slow the spread of some organisms.

Rotate plants. Don't plant the same vegetables in the same place year after year. Otherwise, you create a nursery for disease. Move things around as described in Chapter 16.

Mulch your beds. A layer of mulch on the soil can act like a physical barrier, keeping disease spores in the soil and off the plants. See Chapter 15 for more on mulches.

Watching out for common diseases

The following list includes tips on how to prevent, identify, and treat (if possible) some common diseases that affect vegetables. Controls for diseases that are most troublesome for a specific vegetable are included with the description of that vegetable in Part II. Here are some diseases to keep an eye out for:

Damping off: This disease attacks the bases of seedling stems, causing them to wilt and fall over. I discuss ways to prevent damping off in Chapter 13, which covers all aspects of growing vegetables from seed.

Powdery mildew: This fungus coats leaves and flowers with a white powder. It's most common when days are warm but nights are cool. This disease is particularly troublesome to squash, cucumbers, melons, and peas. Controlling powdery mildew is difficult, but resistant varieties are available. The disease becomes less of a problem as the weather changes.

Some gardeners have had some success using a home remedy. Mix 1 tablespoon of summer oil and 1 to 2 teaspoons of baking soda in 1 gallon of water, and then spray the mixture often to protect new foliage. This mixture also is sold commercially under names such as Remedy. Some forms of neem oil also are registered for use on vegetables. A new biological spray called Serenade (Bacillus subtilis) contains a bacterium that attacks powdery mildew and other fungi.

Root rots: A number of soilborne fungi cause plants to have basically the same damage — regardless of whether the soil is moist. Lettuce is notorious for dying like this. The best way to prevent root rot is to make sure that soil drainage is good and to avoid overwatering — let the soil dry partially between waterings. Otherwise, all you can do to control root rot is to remove the dead plants. Few other control measures are effective.

Southern blight: This rather nasty disease that affects corn is common in the southeastern United States. Southern blight causes plants to rot at the base of their stems, wilt, turn yellow, and die. Unfortunately, this disease is difficult to control. Your best bet is to rotate your crops each year, get rid of all infected plant material, and turn your soil in the fall. You also can try soil solarization, as described in Chapter 15.

Viruses: These diseases affect many vegetables, including tomatoes, peppers, peas, beans, cucumbers, beets, potatoes, and squash. When infected with a virus, leaves and fruits often have mottled yellow spottings and are deformed. Plants are stunted and die young, often not producing usable fruit. Virus diseases are sometimes specific to certain vegetables and spread by insects such as cucumber beetles (see Chapter 8 for more on controlling this pest), aphids, and whiteflies; stopping these pests many times stops the disease. You also should destroy infected plants and try to plant disease-resistant varieties.

Keeping the Animal Kingdom at Bay

Besides insects and diseases, you also should keep an eye out for the 2- and 4-footed pests described in this section. If you have problems with critters, be sure to properly identify the culprit; identification may take some late-night work with a flashlight. What control you use will depend on who's doing the damage.

As you read the control suggestions in this section, you'll notice that fencing is one of my most common recommendations. But even a sturdy fence isn't a 100-percent guarantee, so live trapping and relocating may be the only solution to an especially persistent woodchuck or raccoon. (Check with your state Fish and Game Department to find out whether it has any regulations governing the trapping of the animal you have in mind.) You can buy live traps at most hardware stores; get the appropriate size for the animal that you want to catch. After you have the animal in the trap, release it in areas recommended by your local state Fish and Game Department officials.

Letting your family dog or cat prowl your grounds to ward off wild animals may sound like a good idea, but, in reality, keeping your pets indoors or restrained is the best idea, especially when large animals are around. Rabies is a problem with many wild animals, such as raccoons, and some wildlife, such as woodchucks, which are ferocious fighters.

The following list identifies animal pests that are common to vegetable gardens. It also provides some methods to control these critters:

Birds: Starlings and crows have an uncanny sense of where you planted your corn seeds. To keep birds from eating seeds or pulling up newly sprouted plants, protect your seedbed with a bird tunnel (see Figure 17-4) or a floating row cover. By the time the plants outgrow the cover, they're no longer appetizing to birds.

Cats and dogs: Fences work best to keep four-legged friends — and your neighbors — out of your garden. Cats are a problem early in the season when they like to dig in newly tilled ground; laying chicken wire, pruned rose or raspberry canes, or hardware cloth over your seedbed until plants sprout encourages cats to dig elsewhere. Try spraying a pepper and garlic spray (see the earlier section "Methods of attack" for details) to deter these critters.

Deer: A slanted fence can keep Bambi and her fawns out of your garden. Their instinct is to try to crawl under a fence before jumping it, and they're less likely to jump a wide fence. A slanted fence can be 4 to 5 feet high (see Figure 17-5); a vertical fence must be at least 8 feet high to keep deer from jumping over it.

Gophers: Gophers can wreak havoc by eating plants' roots and underground parts. Trapping is the most practical solution in most cases. Probe the soil near a fresh mound of dirt with a crowbar, and set two traps in the runway, one facing each direction. Tie the traps together and cover them lightly with soil to keep out light.

If your garden is small or organized into small beds, you may want to construct a gopher barrier, as shown in Figure 17-6. Dig the soil out of the bed to a depth of at least 12 inches and line the bottom and sides with 1-inch chicken wire. Then replace the soil.

Mice and small rodents: A 12-inch-high fence made of 1/4-inch mesh hardware cloth, with another 12 inches buried underground, keeps mice and other small rodents out of your garden.

Moles: Moles don't feed on plants; they eat insects such as grubs and earthworms. However, their tunneling may damage the roots of your plants. The most effective way to control moles is to repel them. Moles don't like the smell of castor oil, so spray a mole repellent, such as Mole Med, that contains castor oil.

If the problem is severe, set traps in the tunnels. To find active tunnels, tamp down raised soil, which indicates tunneling. The tunnels that are raised the day after you tamp the soil are active.

Rabbits: A 2-foot-high fence made of 1 1/2-inch mesh should keep rabbits out of your garden. Make sure the bottom is tight to the ground or bury the bottom edge as recommended for woodchucks. You also can try a pepper and garlic spray designed to repel cats and dogs.

Raccoons: A 4-foot-high fence similar to the one recommended for woodchucks usually keeps raccoons out of your garden.

Woodchucks: A fence at least 3 feet high with another 12 inches underground, curved away from the garden, is the best way to keep out woodchucks, also known as groundhogs (see Figure 17-7). Leave the top 18 inches of the fence unattached to support posts. This way, as the woodchuck attempts to climb over the fence, the fence will bend back down under the animal's weight. A strand of electric wire on top of a wire fence also discourages them.