Insects Friends And Foes

9. Insects: Friends And Foes

An organic gardener does not try to destroy the entire insect population in his garden. Not only is this the epitome of futility, but it is neither necessary nor advisable. There will be some insect damage, no matter what is done. Ignore the early signs, and don’t feel you must do something about it, unless your crop is threatened. Eventually, you will learn to recognize your friends in the insect population: the ladybug, the praying mantis, beneficial beetles, flies, wasps, lacewing flies, fireflies, dragonflies, and spiders. They are predator insects whose food is the scavenger insects, preventing them from increasing to dangerous levels.

The first step to insect control is, of course, the building of a living soil, containing all the substances necessary to produce healthy, disease-resistant and insect-resistant plants. Next, be sure to provide adequate moisture for your garden. Your permanent mulch will help to conserve the moisture, and will create conditions which discourage many insect pests.

9.1 Companion Planting

An important step in insect control is companion pluming. Wild plants almost always grow in mixed communities, where each type of plant contributes to the support of others growing nearby.

Even when plant species are mixed with no planned basis, insect problems are reduced. The more of the same plant you have growing together, the more insects are attracted, as they get the clear signals from the larger planting. Interplanting and aromatic herbs confuse their sensory apparatus.

Companion plants influence, complement or supplement each other, and grow in harmony together. Mixed plantings tend to create and maintain a natural balance between beneficial and destructive organisms.

Members of the same plant families, which are subject to the same pests and diseases, should be separated—like tomatoes and potatoes; cucumbers, melons, and squash; and cabbage, broccoli, and cauliflower.

Legumes capture nitrogen from the air, feed it to adjoining plants, and enrich the soil in which they grow. Beans, corn, and cucumbers like to grow together. Or plant beans with eggplant and rosemary. Soybeans, especially, deter chinch bugs and Japanese beetles. Plant peas, leaf lettuce, strawberries and cucumbers with carrots, radishes and chives; turnips with peas; onions and garlic with most vegetables except legumes. Beets and onions are compatible; so are leeks and celery. Plant cabbage, broccoli or Brussels sprouts with beets, kohlrabi, and cucumbers.

Tomatoes are good with onions, parsley, carrots, and marigolds, but do not like kohlrabi. Bush beans like beets and potatoes. The strong scent of marigold seems to act as a deterrent to insects throughout the garden, and their roots secrete a substance that kills nematodes. Be sure to plant some around tomatoes and beans.

Some plants need a lot of light and are excellent companions to those that need partial shade. Lettuce likes cabbage and beets, but can also be put under tall plants that provide some shade. Deep rooting plants bring up the minerals from the subsoil, enriching the top layer, and they aerate the soil for plants with a shallow root system.

Plant nasturtiums in your vegetable garden near broccoli, cabbage, cauliflower, and cucumbers, and between fruit trees, to repel aphids. Chives and onions will also repel aphids. Garlic will prevent bacteria damage and damage from peach borers. Garlic and onions will deter most pests, but don’t plant any near beans or peas. Most strong smelling plants are useful in repelling pests.

There is a long list of companion plants, vegetable preferences and insect repellent plants and herbs. You will find such a list in the article section.

Companion planting, and the use of insect repellent plants, will not prevent insect damage, but will reduce it considerably; it will be a profitable investment.

9.2 Crop Rotation

Crop rotation can help to prevent and control perpetuation of many problems, such as depletion of particular trace elements in specific areas of your garden, and perpetuating insect problems or diseases that can survive in the soil from one year to the next. Implementation of the available information about crop rotation can contribute to a successful garden.

If you are maintaining a permanent mulch, crop rotation may not be absolutely necessary, but it is still an excellent idea, and it does not entail a great deal of extra trouble to relocate plantings each year. If you would rather not bother rotating, but will maintain a permanent mulch and keep building the soil, try doing without the crop rotation; you may find it will not be necessary in your garden. However, I believe rotation to be a good precautionary measure at least in the second and third years of your garden, even if you decide to abandon this procedure after your soil has been built up.

For those who do want to take advantage of crop rotation, here are some suggestions:

Avoid growing the same vegetables (or crops of the same family) in the same location more than once every three years. Plants subject to the same problems should not follow each other in the same bed. Don’t use successive plantings of lettuce, cabbage, or celery in the same soil. They are subject to the same fungus attacks.

Cucurbits (cucumbers, squashes, pumpkins, gourds, melons) should not be grown near any other
member of the gourd family, and there should be a lapse of at least three years between plantings of any of these in a specific area in order to reduce the risk of the fungus disease anthracnose.

Heavy feeders should be followed by light feeders. Leaf crops consume large amounts of nitrogen from the soil, root crops use up the potash, so don’t plant turnips after carrots, nor lettuce in the same bed, year after year.

Legumes (peas, beans) are excellent to precede or follow potatoes, but not to precede sweet potatoes. Members of the cabbage family, or lettuce, are excellent choices to follow legumes.

A rotation chart for vegetables to follow legumes (Organic Gardening, March 1974) suggested cabbage, broccoli, Brussels sprouts, mustard greens, lettuce, and parsley, as first choices; corn, leeks, shallots, radishes, turnips, onions, and Irish potatoes as second choices; tomatoes, eggplant, peppers, and okra as third choices; and suggested that the following vegetables not be used behind legumes: carrots, beets, sweet potatoes, cantaloupes, pumpkins, cucumbers, squash. The varieties of legumes upon which the experiments were based were: Crowder, Purple Hull, Silver Skin, and English Peas; and Bush Lima, Pole Lima, Bunch Snap, and Pole Snap Beans.

Leaf vegetables or cucumbers that have had lots of compost may precede or follow potatoes. Potatoes should never follow tomatoes or vice versa.

Don’t plant peppers where cucumbers have grown within the last year.

Be sure to grow a variety of vegetables and don’t be afraid to experiment. Failures with some will be offset by successes with others, just as in any other method of gardening.

Crop rotation is so little trouble that it seems a shame to overlook this method of increasing the potential of your garden.

9.3 Biological and Logical Insect Controls

Start out with the idea that some insect controls will be necessary, especially in the initial period before your soil has been built up. You may want to try biological controls like praying mantis egg cases, Trichodrama wasp eggs, or imported lady bugs—success with these varies. The problem with these imported insects is that they may soon migrate to another location that suits them better.

Another very successful biological insect control is the presence of birds, toads, lizards, etc. Provide trees, bird-houses, bird baths and bird feeders, and shallow pans of water on the ground for the toads and lizards, who will also appreciate shrubbery and mulch.

Sanitation and good housekeeping in your garden will prevent a lot of problems. Carefully remove and destroy all diseased plants and wash your hands thoroughly before handling other plants. Remove all dropped fruit and garden trash. Watchfulness and handpicking is an old-fashioned, but effective, method of controlling some insects.

Cardboard collars around the stems of your plants help to ward off cutworms. Aluminum foil collars around young seedlings keep off fleas, reflect the rays of the sun and give the plant more warmth.

Other effective insect controls are wood ashes, black pepper, lime, or rock phosphate dust mixed with water, and a homemade spray or drench of garlic, onions, hot red peppers (and a little soap to make it stick). A good recipe is one cup hot peppers, three whole garlic bulbs, three medium onions. Blend with one pint water (or a little more). Strain, add enough water to make one gallon, and apply to both under and on top of leaves. It is easier to use this in a sprinkling can, as it may clog the sprayer, but you may have to use a spray for the undersides of the leaves.

Beer (or a solution of baking yeast, or any other ferment) in a shallow dish attracts slugs—and drowns them. Wet areas are their hiding places.

Rye flour or clay, dusted on plants when the morning dew is fresh, will trap soft-bodied insects and the sunshine will bake them.

Decayed insect sprays or drenches are useful. Insects are repelled by the scent of dead bodies of their own species.

A spray or drench of soapsuds is effective against aphids, mites, and plant lice. Rinse with clear water within a few minutes.

Some experiments made in 1979 at the University of California, showed that soap solutions can be used effectively to combat a number of plant-feeding insects. Among the soaps which were included in the experiments were “Shaklee’s Basic H” and “Fels Naphtha Laundry Bar” soap. The least damage to plants was achieved when the liquid formulations were used at 1% to 2% (7 teaspoons to 5 tablespoons to the gallon); and bar soaps or powders at 1.5 to 2 ounces per gallon of water. More concentrated solutions provided more effective control, but also increased the potential for plant damage. Of course, soap solutions do not have any residual activity, and repeated applications are necessary. However, even when applied only once or twice a year, beneficial results are achieved. It is best to use soap, not detergent. Three tablespoons of “Ivory Flakes” to a gallon of tepid water is safe and effective.

9.4 Insecticides, Repellents, Fungicides

If you must resort to insecticides for your garden and trees, some which will not poison your food are available. A dormant oil spray, obtainable at nurseries, in a 3% miscible solution, may be used during the dormant period on certain fruit trees, and also, in a weaker dilution, as a spring and summer spray, to control certain insects. This is an effective control for many sucking and chewing insects, including aphids, thrips, scale insects, mites, red spiders, white flies, and mealy bugs. The eggs of codling moths, oriental fruit moths, leaf rollers, and cankerworms are also destroyed.

A one-time application of “Milky Disease Spore Powder” (called “milky” because it causes an abnormal white coloring in the insect) will prevent damage by Japanese beetles on your property and your neighbor’s, since it spreads underground. It is supposed to be harmless to everything except the Japanese beetle grub.

An excellent multipurpose control of caterpillars and chewing insects is the product “Thuricide” (another spore-type pest disease, called Bacillus Thuringiensis) which is extremely efficient for use in the vegetable garden on vines and fruit trees, and kills more than 100 species of harmful insects. The instructions say this product may be used up to the day of harvest. To be effective, the leaves of the plants must be ingested by the insects, as “Thuricide” is a stomach poison for them. “Dipel” is another manufacturer’s name for the same formulation.

Most diseases exhibit specific symptoms, so it is not too difficult to differentiate from insect damage. It is not difficult to identify insect damage caused by sucking insects like aphids or thrips, and chewing insects like caterpillars.

Sucking insects cause leaves to curl and become spotted, or they may turn yellowish, stippled white, or gray. These insects and their brownish eggs or excrement can often be seen on the underside of the leaves.

Aphids cause curling or cupped leaves, or round or conical protrusions. Thrips leave a black deposit of tiny specks, or whitish streaks.

Caterpillars, grasshoppers, weevils, and flea beetles are some of the chewing insects which eat the leaves. Flea beetles make tiny round perforations; weevils produce angular holes, beetle larvae (grubs) skeletonize leaves, eating everything but the veins.

Red spider mites, which are so tiny they are practically invisible, deposit tiny tents of fine cobwebs on terminal leaves, and can be found (with a magnifying glass) on the underside of the leaves—under a strong magnifying glass in a good light, you may see tiny specks about the size of fine meal.

Cyclamen mites cause deformed leaves; leaf miners produce blotches or tunnels. Round or coned protrusions can be caused by either midges or gall wasps.

Both nematodes and gall wasps can cause the partial or total collapse of a plant.

A useful product suitable for organic gardeners is “Neutral Copper” by Southern AG, a fungicide which, when used according to directions, will control many plant diseases, without poisoning your food. I have not found it necessary to use the neutral copper spray on any of our vegetables, but have used it on avocado trees, citrus trees, and some grape vines. It should be used, sparingly, at the first signs of disease. It may also be used as a precautionary measure on avocados, mangos, citrus, and some varieties of grape vines (not necessary for muscadine grapes) to avoid infection from scab and antracnose and some other diseases. These plants are subject to such diseases (which may be averted through the occasional use of a fungicide).

The best time to apply neutral copper as a preventive of disease is just before new growth starts in the spring, and when two-thirds of the petals have fallen. It is not advisable to use a neutral copper spray in the fall on your citrus or other fruit, as its use at that time of the year may prevent the fruit from sweetening. If disease problems occur at this time of the year, just prune out the infected leaves and dead wood.

Some of the specific symptoms of plant diseases are:

1. Brown circular spots on fruit, or dieback of twigs and loss of leaves about a foot from the tips (fungus).
2. Rust—leaves look like they are covered with rusty powder (fungus).
3. Fire blight—drying up of blossoms, blossom stems, or fruit (bacterium Erwinia amylovora).
4. Dark brown spots in leaves with small pinpoint-like objects (fungus).
5. Grayish-white leaf with brown margin (mildew).
6. Discoloration of stem at ground level—slick and slimy (damping off).
7. Leaves that show watersoaked areas within leaf (bacterial infection).
8. Circular spots with definite color around the outside of the infected spot (fungus).
9. Leaf gall (azaleas)—thick growth causing excessive cells (fungus).
10. Mold on plants may be due to location in a cool, damp, sunless area.

One should use a little soap (not detergent) as a spreader-sticker for all sprays, so they will adhere to the plants, instead of running off. The products referred to above usually need to be used only rarely and sparingly. It doesn’t take long to learn to recognize insect damage or disease and to evaluate the necessity for controls. Most healthy plants, however, rarely need controls.

Tobacco stem mulch will repel aphids, flea beetles, and thrips, but should be used cautiously, if at all. Some plants, like tomatoes, don’t like tobacco; and the nicotine content of such a mulch may kill beneficial earthworms, insects, and organisms. Tobacco could also carry disease to some of your plants, especially potatoes, eggplants, tomatoes, or peppers. I don’t use tobacco stem mulch.

Black leaf— a nicotine spray—may be used as an emergency treatment for aphids, thrips, or other small insects, but use it only if you must. It is subject to many of the objections listed above for tobacco mulch. I don’t use “Black Leaf.”

In extreme cases for emergency use only for a severe infestation, it might be necessary to use one of the insecticides made from rotenone, pyrethrum, ryania, or quassia, which are plant extractives. “Sevin” (available at nurseries and garden supply stores) is such an insecticide, and will control the bean leaf roller and the bean skeletonizer, and various other insects, but you ought to first try “Thuricide” for these problems.

The plant extractive insecticides, such as “Sevin,” should be discontinued completely as soon as moderate control has been attained. They are not completely hamless, but there will be no residue if you wait fourteen days before harvesting. I have never resorted to these insectides, and, of course, would never even consider the use of a more dangerous insecticides like “Malathion.”

If you would like acceleration in your recognition of insect damage, diseases, deficiencies, and problems in your garden, and want to study the subject, see pages 590-91 (deficiencies) and pages 340-51 (diseases) in Rodale’s How to Grow Vegetables and Fruits by the Organic Method and The Bug Book by John and Helen Philbrick.

Gil Whitton, Pinellas County (Florida) Agriculture, recommends Cynthia Westcott’s Plant Disease Handbook, which is available in libraries as a reference book. As Mr. Whitton says (St. Petersburg, Florida Independent, 3/6/75), “No one book or person can have all the answers.”

If you have problems with “raiders” (rabbits or other small animals), this can be very frustrating. The best solution is a fence to keep them out. See the article in this lesson, “Containing Inhibits Raiders.”