Vegetable Gardening (120 page)

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.