MININPUTS (minimum inputs) GARDENING

MANAGING GARDEN PESTS -- THE EASY WAY
(SOMETIMES ERRONEOUSLY CALLED "ORGANIC GARDENING"!)

Jerry Parsons, Roland Roberts, and Larry Stein
Texas Cooperative Extension

Insects and diseases are without doubt the biggest obstacles to successful productive gardening in Texas. Every year, literally millions of dollars worth of our state's garden and commercially-grown fruits and vegetables are lost due to the destructive feeding of insects and the rot and decay caused by diseases.

If you have been gardening for any length of time, chances are you have experienced serious, if not devastating, losses due to insects and diseases. Garden spots seem to be inhabited with every and any disease known to mankind -- plus a few others! You probably have experienced the feeling that thousands of insects have gathered in your back yard to gorge themselves on your garden vegetables. To make things worse, many insects seem to "come to the seed" -- how else could they know about your emerging bean seedlings and new tomato plants? And if it's not hungry insects, just about the time your garden appears to have a bright and productive future, mildews, rusts, and blights seem to show up overnight to ruin your chances for a good crop of garden-fresh vegetables.

Because of the abundance of insects and diseases, vegetable gardening can best be described as a real challenge. It's primarily a challenge because of our long growing season and relatively mild winter -- the very reasons vegetable gardening is so popular and potentially rewarding . The challenge is real but it can be overcome.

To many gardeners, the obvious way to meet this challenge is to have a good sprayer and the necessary pesticides to control commonly-occurring insects and diseases. Controlling pests with pesticides may indeed become necessary, and pesticides can be highly effective and completely safe if used properly. However, before resorting to pesticides, the first and most effective way to reduce losses caused by insects and diseases is prevention.

Prevention is really nothing more than common sense and sound, sensible gardening practices. Through continuous and methodical use of the following practices, many problems can be greatly reduced, if not completely overcome.

SMART PURCHASING. When purchasing seed and transplants, make absolutely certain you do not take problems home with you. Buy only seed produced for current gardening season that has been treated with fungicides to prevent seed rot and seedling diseases. When selecting transplants, look for those that appear healthy, have good color, and are free of holes in the leaves or spots/lesions on the stems and foliage, which could indicate the presence of insects or diseases.

USE RESISTANT VARIETIES. Always plant resistant, recommended varieties in your garden. Plant breeders have done an excellent job in recent years developing high-yield, top-quality varieties that have resistance to many common diseases. Resistance means slower disease development, allowing resistant plants to produce an acceptable yield before or without losing vigor to disease attack. Unfortunately, developing resistance to insects is much more difficult, but this too will one day be a reality. Check with your local county Extension office or reputable nurseryman for the best varieties to plant in your garden.

PROPER SOIL PREPARATION. Proper preparation of your garden soil will significantly help you prevent losses due to insects and disease. Working in liberal amounts organic matter will improve drainage of soils and help sandy soils hold moisture and nutrients. Organic matter increases the number and kind of microorganisms in the soil. Many of these microorganisms compete with disease agents for nourishment. In some cases, the best organic matter is obtained by turning under a green cover crop such as a small grain (wheat, oats, barley, rye) or a legume. When tilling or spading the soil, be on the lookout for grubworms, wireworms, and other soil insects. If found in high numbers application of a recommended soil insecticide prior to planting will prevent serious problems in the future. Summer cultivation will also prove helpful.

ADEQUATE FERTILIZATION. Test your garden soil to determine its pH and the proper amount of fertilizer to apply. Vegetables grown in soils that are too acidic or too alkaline will grow poorly or not at all, making them highly susceptible to problems. The right amount of nutrients in the soil will result in healthy, vigorous plants that are less affected by insects and diseases. However, use of too much fertilizer can result in rank-growing, highly succulent plants, and may encourage insect and disease problems.

CHANGES IN PLANTING TIME. This will often reduce plant damage or keep insect pests separated from susceptible stages of the host plant. Delayed planting until the soil is warm enough for corn and bean seeds to germinate quickly reduces seed maggot damage. Hot caps (milk cartons, paper sacks or similar materials placed over plants) used during the early season not only will preserve heat, but also will protect plants from damaging wind, hail and insects. In some situations a healthy transplant will overcome insect damage more easily than a small plant developing from seed in the field.

MECHANICAL CONTROL METHODS. Mechanical control methods usually are more practical for a small garden than for a large one. They can be used singly or in combination to obtain desired results.

Preventive devices often are easy to use, although their effectiveness varies. Such devices include: (1) paper collars around the stems of plants to prevent cutworm damage; (2) Grow-Web fabric for hot beds and cold frames to prevent insect egg-laying; (3) Grow-Web or mesh covers for small fruit trees, berry bushes, tomatoes and other plants to keep out large insects and birds.

Hand-picking of insects and insect egg masses insures quick and positive control. This method is especially effective with foliage-feeding insects such as bean beetles, potato beetles, hornworms and squash bugs.

There may be times when gardeners can use a fine stream of water under pressure to dislodge insects from plant stems and leaves -- a method often used to control spider mites. This also increases humidity around the leaves which helps bring spider mite infestations under control. The stream of water can physically remove some insects, especially aphids, and when dislodged they fail to return to the plant. Care should be taken to use water pressure only on sturdy plants to avoid plant damage.

Various types of traps are reportedly successful in reducing garden insect numbers. For example: (1) earwigs can be trapped in rolled up newspapers placed in the garden or other locations where these insects gather; (2) slugs and pillbugs can be trapped under boards placed on the ground; (3) a small pan placed flush with the soil and filled with stale beer will attract and kill slugs and snails; and (4) a two-quart container, half-filled with a 10 percent solution of molasses and water will attract and trap grasshoppers and certain beetles.

Blacklight traps are a reasonably good tool for monitoring insect species in a given area, but usually provide little protection for the garden. Light traps attract both harmful and beneficial insects that ordinarily would not be found in the area. These insects may not be caught in the traps, but may remain in the area, and the harmful ones may cause damage later. Also, some species such as wingless insects and those insects only active in the daytime are not caught in the traps. Consequently, the value of blacklight traps in the home garden is questionable. Where blacklights are used, it is recommended that they be placed 50 to 75 feet away from the area which is to be protected.

USE BIOLOGICAL CONTROL METHODS. Generally. biological control can be defined as the direct or indirect use of parasites, predators or pathogens (bacteria, viruses, fungi, protozoans) to hold pest insect populations at low levels to avoid economic losses. Biological control methods fall into three categories: (1) introduction of natural enemies which are not native to the area (these enemies must then establish and perpetuate themselves); (2) enlarging existing populations of natural enemies by collecting, rearing and releasing additional bio-control agents; and (3) conservation of beneficial organisms by such means as the judicious use of pesticides and the maintenance of alternate host insects so parasites and predators can continue to develop.

It is not yet possible to reliably predict how effective the introduction of a given parasite or predator will be. However, certain factors can indicate the potential value of a natural enemy. The effectiveness of a parasite or predator is usually related to: (1) its ability to find a host when host numbers are small; (2) its ability to survive in all places where the host insect lives; (3) its ability to use alternate hosts when primary hosts are in short supply, (4) its high reproductive ability to reproduce rapidly over a short period of time; and (5) its ability to adapt its life cycle with that of the host so that the desirable host stage is available for development.

Many beneficial organisms occur naturally in the garden, but often they are not numerous enough to control a pest before it inflicts severe damage. In fact parasites and predators appear to be most effective when a pest population has stabilized or is relatively low. Their influence on an increasing pest population is usually minimal since any increase in parasite and predator numbers depends on an even greater increase in pest numbers. Pathogens, however, seem to be most effective when pest populations are large. Consequently, the nature of the host insect-natural enemy relationship makes it impossible to have an insect-free garden and at the same time maintain sizable populations of beneficial insects.

Numerous bio-control agents are available. Following is a list of some of the more popular bio-control agents:

Bacillus thuringiensis
This bacterial insecticide provides effective control of the larvae of several moths and butterflies. The bacterial spores are harmless to warm-blooded animals and beneficial insects. Bacillus thuringeinsis is available in three formulas : "I" for mosquitos and fungus knats, "K" for larvae of moths and butterflies; and San Diago for potato beetles. Some of the brand names of these Bacillus products are:
B.t.i. - Abbott; VectoBac 12AS-II, VectoBac AS
B.t. kurstakiAbbott - Dipel 2X, Dipel 2X WDG, Dipel SG, Dipel ES, Xentari , Dipel ES-NT, Dipel 2X WDG, Dipel 10G
B.t. kurstaki - Sandoz; Javelin WG, Thuricide 48 LV

Bacillus popilliae - (milky disease bacteria)
This bacterial insecticide controls grubs of Japanese beetles in the eastern U.S., and some testing has been done for control of white grubs (Phyllophaga spp. and Cotinis spp.) in Texas. It has not been effective against the principal white grub species in Texas.

Nosema locustae
- is a spore (Protozoan) used to control grasshoppers. The material is sprayed on the plants which grasshoppers ingest. The spores germinate inside the grasshopper, causing death. Control is extremely slow and homeowners may not be satisfied with results. Baits have proven more effective.

Trichogramma wasp
Adult wasps are available from several sources. The tiny wasps attack the eggs of more than 200 pest species, including cutworms, armyworms, fruitworms and many moth and butterfly eggs deposited in orchards and field crops. Wasps should be released when the moths are first seen, but a sequence of releases throughout the season is preferable to a single, large release. Results will depend on the timing of the releases, selection of Trichogramma species, and placement of wasps near host egg masses.

Green lacewings (Chrysopa)
Eggs are sometimes available. The larvae, known as aphid lions, prey on many garden pests including aphids, spider mites, leafhoppers, thrips, moth eggs and small larvae. Adult lacewings feed on honeydew, nectar and pollen. Lacewings introduced into the garden must have a readily available supply of food or they will leave.

Praying Mantid
Egg cases containing about 200 individual eggs are available from a number of sources. The mantid is a voracious predator. In addition, it is cannibalistic immediately after hatching, so few nymphs survive the first week of life. But the mantid is a poor searcher for food and usually waits for prey to come to it. This greatly influences the kinds of insects it captures and kills. Food preferences include grasshoppers, crickets, bees, wasps and flies.

Lady beetles
Adult beetles are available from several sources. Aphids are the preferred hosts, but lady beetles will eat mealybugs, spider mites and certain other soft-bodied pests and eggs. They do not, however, kill grubs, caterpillars and other beetles. Lady beetles do feed on small larvae such as green loopers especially the ash gray lady beetle. Unless an ample supply of live aphids or other hosts are available at the release point, lady beetles will disperse and leave the area. In some cases, most of the beetles will leave the area regardless of the availability of food. Lady beetles can be encouraged to remain on a plant by using small meshed screen cages. Remove cages before they devour all of their food supply. In hot dry weather these beetles enter a nonactive (aestivation) state. Feeding and reproduction cease. Little control from lady beetles can be expected during this time.

One source of the above mentioned biological controls is:

1996 PRICE LIST

A-1 UNIQUE INSECT CONTROL

5504 Sperry Dr. Citrus Heights, CA 95621
(916) 961-7945 Fax (916) 967-7082

LADYBUGS; Available all year:
small (pint) $6.05
medium (pint) $10.30
large (quart) $15.40
1/2 gallon $27.50
gallon $48.50

PRAYING MANTIS EGG CASES: Available January - June
3 for $ 4.85
7 for $ 9.70
20 for $23.10

FLY PARASITES: Available all year:
2,000 for $8.80
4,000 for $15.40
8,000 for $27.50

LACEWING EGGS: Available all year
1,000 for $7.15
5,000 for $27.50

TRICHOGRAMMA: Available all year
1 packet (5,000) for $2.90
3 packets (15,000) for $10.95
5 packets (25,000) for $17.95
10 packets (50,000) for $25.00
25 packets (125,000) for $28.85

EARTHWORMS: Available all year
small container for $13.75
large container for $16.50

BENEFICIAL NEMATODES (BioSafe 100); Available all year
1 for $26.40

NATURAL INSECTICIDES. Despite all efforts, at times non-insecticidal methods will fail to prevent excessive insect damage in the garden. At such times, the use of insecticides may be the only alternative left to save the crop. Insecticides chosen should have low toxicity for humans and other warm-blooded animals. They should be used only when needed and according to label directions. A better understanding of insecticides will enable you to use these materials more effectively, and to realize that they can be an aid without necessarily harming you or the environment.

When insect damage becomes great enough to warrant emergency measures, a decision must be made whether to use natural insecticides and various homemade botanical sprays or modern synthetic chemicals. However, some synthetic materials are actually less toxic and more efficient than some of the natural insecticides.

"Safe" and "natural" products also have "poisonous" ingredients such as the products listed below:

Active Ingredient Active Ingredient
B.T. aizawaiNerolidol
B.T. aizawai GC-91Nicosulfuron
B.T. israelensisNosema locustae
B.T. kurstaki Octyl bicyloheptenedicarboxamide
B.t. kurstaki HD-263Oxytetracycle hydrochloride
B.t. kurstaki EG2348 Paradichlorbenzene
B.t. kurstaki EG2371 Paraffin oils
B.t. kurstaki EG2424 Periplenone B
B.t. san diegoPolyhedral inclusion bodies of
B.t. tenebrionis Autographa californica NPV
Bacillus popilliaePolyhedral inclusion bodies of
Bacillus lentimorbusHeliothis zea NPV
Bacillus sphaericus or Helicoverpa zea NPV
Bacillus subtilis GB03Polyhedral inclusion bodies of
Bacillus subtilis MBI 600beet armyworm NPV
Diatomaceous earths-Kinoprene

The bottleneck produced by the cumbersome the maze of bureaucratic gymnastics Environmental Protection Agency (EPA) requires registrants to perform prevents most safe pesticides from receiving favorable treatment. Now they must go through the long, precarious amendment process.

Following is information about some natural insecticides:

  1. Pyrethrum - Botanical insecticide. This slightly toxic insecticide is derived from the flowers of a species of Chrysanthemum imported mainly from Kenya and Ecuador. The material causes rapid paralysis of most insects, but the insects usually recover unless the pyrethrum is used in combination with a synergist or other poison. Pyrethrum mixed with synergists such as piperonyl cyclonene to increase toxicity and produce longer residual action is used extensively in space sprays, household sprays, crops sprays and dusts. This chemical is registered for use on most vegetables and fruits at any time during the growing season.
  2. Nicotine - Botanical insecticide. Pure nicotine is a tobacco extract highly toxic to warm-blooded animals. The insecticide usually is marketed as a 40 percent liquid concentrate of nicotine sulfate, which is diluted in water and applied as a spray. Dusts can irritate the skin and are not normally available for garden use. Nicotine is used primarily for piercing-sucking insects such as aphids, whiteflies, leafhoppers and thrips. Nicotine is more effective when applied during warm weather. It degrades quickly, so can be used on many food plants nearing harvest. It is registered for use on a wide range of vegetable and fruit crops. This product is becoming difficult to find.
  3. Sabadilla - Botanical insecticide. Sabadilla is obtained from the seeds of a lily-like plant and acts as both a contact and stomach poison for insects. It is not particularly toxic to mammals, but does cause irritation of the eyes and respiratory tract. A mask should be worn when working with this insecticide. This material deteriorates rapidly upon exposure to light and can be used safely on food crops shortly before harvest. Sabadilla generally is used as a 5 to 20 percent dust or as a spray. This product is becoming difficult to find.
  4. Rotenone - Botanical insecticide. Rotenone is extracted from the roots of Derris plants in Asia and cube plants in South America. This general garden insecticide is harmless to plants, highly toxic to fish and many insects, moderately toxic to mammals, and leaves no harmful residues on vegetable crops. It acts as both a contact and stomach poison to insects. It is slow acting, and in the presence of sun and air, its effectiveness is lost within a week after application. Wear a mask during application because rotenone can irritate the respiratory tract. Rotenone dusts and sprays have been used for years to control aphids, certain beetles and caterpillars on plants as well as fleas and lice on animals.
OTHER PESTICIDES. Gardeners have been using soap to control insects since the early 1800's. During the first half of the 19th Century, whale oil soap, and more commonly, fish oil soaps were an important part of insect control. Researchers have not yet determined exactly how soaps work. Some soaps simply wash off the outer waxy coating of the insect cuticle, destroying its watertight nature and causing the insect to dry up and die. Other soaps have additional insecticidal properties which may affect the nervous system. These soaps appear to have toxic activity only against plant-eating insects and thus may spare beneficial insects such as lady beetles, honeybees, lacewings and predatory mites. Although a number of soaps tested have insecticidal properties, only Safer's Insecticidal Soap is currently registered for use on edible crops. It controls such pests as spider mites, aphids, mealybugs, whiteflies, harlequin bugs, stink bugs and thrips.

Gardeners have been using a spray mixture containing onions, garlic and pepper mixed together to control insects for many years. Recent scientific research indicates that the use of these materials has given erratic and in many cases ineffective insect control. Sprays of food-derived substances do not appear to be good choices as a pesticide. However, some success may be achieved with them, but it is likely to be sporadic. Spraying several times a week might help to bring infestations under control. Control with one application should not be expected. Garlic is beginning to show some good results.

SAFE USE OF PESTICIDES. When it is necessary to use insecticides to protect the garden, use them wisely and safely. The following tips will help you make better use of insecticides:

  1. Inspect the entire garden at least weekly to monitor insect numbers and activity. Pay particular attention to the underside of leaves where mites, whiteflies, aphids and insect eggs occur. If treatments are applied when an infestation first starts, insect numbers can be maintained at lower levels much more easily, and with smaller amounts of chemicals.
  2. Apply insecticides to all plant surfaces so that an insect anywhere on the plant will be exposed to a lethal amount of the chemical. Do not apply insecticides to wilted plants or during the hottest part of the day. Apply dusts only when the wind is calm and plants are dry. Sprays should be applied when the wind is no more than 5 to 10 mph. Retreatment may be necessary after a rain.
  3. Apply insecticides only at recommended dosages: increased amounts can be dangerous, cause plant damage and leave harmful residues without improving insect control.
  4. The length of effective control of insecticides varies widely. The longevity of toxic properties varies primarily with the product, formulation, water pH and environmental conditions. Temperature, humidity, wind and sunlight affect insecticides. The greater the extremes, the sooner the insecticides are detoxified.
  5. The time interval required by the Environmental Protection Agency between treating a crop and harvesting that crop varies with the insecticide and the crop. This information is posted on the pesticide label to insure that any residues will be within established tolerances at harvest time.
  6. Always read and follow mixing and application instructions on the insecticide label for safe and effective insect control.
In many situations it is helpful to use several control techniques to reduce insect pest populations to low enough levels that insecticides are not required, or are needed only sparingly. With reduced insecticide use, biological control agents can become more effective, insecticide costs will be saved, and you will have the satisfaction of knowing that few, if any poisons were applied to your edible crops.

CROP ROTATION. If your garden has enough space, avoid planting the same vegetables or members of the same vegetable family in the same location for at least two to three years. By rotating vegetables from one location in your garden to another, many soilborne insects and disease problems can be avoided.

Crop grouping for rotation to control soilborne diseases.

GROUP AGROUP BGROUP CGROUP DGROUP EGROUP F
Cantaloupe
Honeydew
Pumpkin
Squash
Watermelon
Brussels sprouts
Cabbage
Cauliflower
Collards
Lettuce
Mustard
Radish
Rutabaga
Spinach
Swiss chard
Turnip
Eggplant
Irish potato
Okra
Pepper
Tomato
Sweet potato
Beet
Carrot
Garlic
Onion
Shallot
Sweet Corn Bean
Cowpea
Peas

PROPER SPACING. Pay close attention to guidelines regarding proper spacing between rows and between plants in the row. Crowded growing conditions result in slow drying and poor air movement, and encourage disease development. Also, if pesticide treatments become necessary, crowded growing conditions make proper application and thorough coverage almost impossible to achieve.

VERTICAL GARDENING. Grow plants upright whenever possible, using cages, trellises, fences, and other types of props. This helps to prevent foliage and fruit from contacting the soil, thereby reducing losses due to soil-related pests. If pesticide use becomes necessary better control with fewer applications is possible with vertically-grown plants. Tomatoes, climbing beans and peas, and several members of the cucurbit family are some of the vegetables well suited to vertical gardening.

WEED CONTROL. Provide early and complete weed control in your garden by mulching, shallow cultivation, or hand removal. Weeds can be a source of inoculum for diseases, and often harbor insects that cause considerable damage by feeding or transmitting diseases. If practical, control weeds in the vicinity of your garden for the same reasons.

GARDEN SANITATION. Garden cleanup is an essential part of insect and disease prevention. During the growing soon, remove any odd-looking, stunted, or sickly plants as soon as possible. Chances are that such plants will never be productive, and may very well be infected with viruses, other diseases, and that will infect healthy plants in your garden. Judicious removal of foliage that appears damaged by diseases or insects will also help prevent spread. Any crop residue destruction practice that reduces the disease agent's ability to reproduce or over season can be included under sanitation. Examples are raking and burning (if not in a restricted area) diseased leaves and disposing of infected fruit. Dig up root knot nematode infected plants and remove as much of the root system as possible from the garden site. Root knot nematodes are harder to kill when protected by root tissue.

Do not pile diseased leaves, fruits and other plant-parts near the garden. Fungi, for instance, often produce thousands of spores in the reproductive process and these spores can be wind- blown great distances. Burn, bury or dispose of diseased plant tissue to prevent dispersal of the disease agent. In most cases, do not put diseased plant parts in a compost pile. This is especially true for nematode-infected plants. Although many disease organisms are destroyed by heat during composting, 100 percent kill is not normally obtained and many people are confused about and consequently do not compost but rather "rot" which does not destroy pathogens. Contaminated compost may spread disease organisms as the compost is being used. Make compost with grass clippings or shrub and tree leaves as the disease organisms on grass and leaves are not likely to affect garden plants.

SUMMER TILLING. If possible and practical, consider leaving part or all of your garden "fallow" or not planted during the summer. Tilling or spading the soil occasionally in the summer will expose nematodes, insects and their eggs to the hot, dry sun and high temperatures, effectively reducing their numbers.

HEAT TREATMENT. Heating small amounts of soil is practical for potting plants and growing seedling transplants. The soil should be moist but not saturated. Heat the soil at 180 F. for approximately 3 hours in a standard oven. Place an average-sized Irish potato in the middle or the soil to act as an indicator. When it is cooked, the soil should be sterile. Microwave ovens can be used for sterilizing small quantities. Using high power, heat the soil for 3 minutes. Do not overheat with either system. Excessive heating releases certain elements in the soil to toxic levels.

A new heating approach that has shown good results in Texas is solarization (soil pasteurization). It consists of covering well-tilled, highly moist soil with clear plastic, sealing the edges and leaving it for several weeks. Do not use black plastic because soil heating is not as great as heating under clear plastic. Best results have been reported with fungi control, principally those causing root rots. Certain weeds and nematodes are controlled but not consistently. Solarization also stimulates plant growth possible by creating a good environment for beneficial microorganisms; however, this phenomenon is not fully understood. Solarization works best during the hottest months; July and August are ideal for home garden sites. Continue the treatment at least one month.

CONTROL ROOT KNOT NEMATODE. No doubt many gardens have become infested by planting contaminated transplants or by bringing in topsoil harboring root knot nematodes. Taking steps to prevent this problem is just as important as implementing steps to control it once it is a problem. Where soils are already infested and a garden is first put into production, nematode levels generally are low. After several years of gardening and growing susceptible plants, nematode populations increase to the point that damage becomes noticeable. Control practices include summer fallowing, rotation, adding organic matter, planting trap crops, removing diseased plants and using resistant varieties. All these control measures are designed to reduce the soil's nematode population.

Benefits of summer fallowing have been discussed. Removing potential hosts and keeping the soil dry also reduces the nematode population as the nematode requires a moist environment for survival. Additional years of fallowing further reduce nematode populations.

Rotating with non-hosts or poor hosts of the root knot nematode is another means of reducing the population. Sweet corn is a poor host and is good to use in a rotation, especially in an area where root knot has done severe damage. Onions, garlic, asparagus and shallots also are poor hosts. Cool-season crops such as cabbage, Irish potatoes, greens (turnips), radishes and broccoli are less likely to suffer yield loss from root knot nematodes. Even though these are susceptible plants, they grow best in cooler temperatures that are not favorable for root knot nematode development.

High soil organic matter alone does not insure root knot nematode control. The higher the organic matter, however, the better the chance that antagonistic organisms will develop. Some soil fungi trap nematodes and use them as a food source. Some organic matter works better than others. Turning under a green manure crop such as small grains or legumes several weeks before planting is the best. Additional nitrogen may be necessary for adequate crop production because decay organisms in the soil use available nitrogen as they break down the green manure crop.

Sometimes people resort to home remedies to control nematodes such as planting marigolds or mixing sugar or lye into the soil. Of these three, only marigolds are effective in controlling nematode populations.

Marigolds secrete toxic compounds of an a-terthienyl type into the soil which kills nematodes but planting a few marigolds around annual plants in infested soil will NOT prevent infection. Marigolds also act as a trap crop. Nematodes enter their roots but are unable to complete their life cycle. Trapped nematodes die without reproducing.

French marigolds, Tagetes patula, are more effective in controlling root knot nematodes than the African marigold, Tagetes erecta, which also is referred to as the American, Big or Aztec marigold. However, the Mari-Mum American marigold will be somewhat effective while beautifying the fall garden site when planted in August. To be effective marigolds must be planted as a solid crop and grown for 90 days to begin secreting the three compounds of an a-terthienyl type to reduce the nematode population.

If marigolds are planted close together, they form a dense canopy which retards weed and grass development. Many weeds and grasses serve as hosts for root knot nematodes. If the weeds are not controlled, marigolds may be unable to suppress the nematode population.

Using marigolds in a manner other than July or August- planted Mari-Mums can invite disaster. For example, planting a few marigolds here and there among tomatoes encourages spider mites. The spider mite is one of the most difficult garden pests to control and can become as serious a problem as the nematodes. Some gardeners claim that spider mites can be controlled by thoroughly spraying infested plants with three tablespoons of liquid sea weed concentrate per gallon of water before populations are extreme. The spray knocks them off and the sea weed supposedly functions as a foliar feed as well.

Remove all nematode-infected plants from the garden as soon as possible after production ceases. Removing the root system eliminates many of the nematodes. To remove as much of the root system as possible, use a shovel rather than just pulling the plant up by the stem.

Root knot resistant vegetable varieties are not plentiful. Fortunately, progress is being made in the development of root knot resistant tomatoes. The best resistance is found in the hybrid varieties developed in recent years. Root knot resistant varieties are noted in seed catalogs by "N" following the variety name. Preceding the "N" are often "V" and "F." "VFN" stands for Verticillium wilt resistance, Fusarium wilt resistance and nematode resistance. Hybrid tomato seed are more expensive than open pollinated seed, but the benefits in disease resistance alone are enough to justify buying them.

Diseases caused by root knot nematodes and other organisms can be prevented with non-chemical methods that either avoid the disease or suppress the disease agent. However, maximum control is only assured when using as many of these disease preventive practices as possible.

PROPER WATERING. When you water is much more important than how you apply water in your garden. Water when the soil is relatively dry an inch or two beneath the surface, not when plants wilt. Plants wilt for many reasons -- insects, diseases, excessive fertilization, as well as too much water! If possible, water in the morning to allow the foliage to dry before the onset of cooler nighttime temperatures. Also, avoid working in your garden when the foliage is wet, to help prevent the spread of diseases from one plant to another.

TIMELY HARVEST. Never allow over-mature produce to remain on your plants or nonproductive plants to remain in your garden. Harvest all vegetables as they mature. Pull and discard nonproductive plants, as they can serve as hosts for diseases and as breeding places for insects.

In addition to these guidelines, your "shadow" in the garden on a regular and timely basis is perhaps the best way to prevent insect and disease problems. Be observant and look for the beginning of possible problems. A hand lens may prove especially useful. Look for webbing, egg masses, individual insects, leaves with spots or lesions, and any other signs of insects and diseases. Remove and discard if found. Try to detect and remedy simple problems before they become serious problems. Gardeners should get an insect book to identify the "good" bugs versus the "bad" bugs which should be controlled. Educating yourself about the "good" and "evil" of garden pest control makes gardening even more enjoyable.

MINIMAL INPUTS POTENTIAL FRUIT & NUT CROPS Agarita Agarita has no serious pest or disease problems. Spring frosts can reduce production. Bird predation on the maturing berries can be significant.

Minimal Inputs Potential: Very high.

Blackberry The most limiting factor to blackberry production is soil pH. Production drops off above pH 7.5 with serious plant growth problems at 8.0 and above. Proper pruning after harvest, elimination of weed growth and selective removal of diseased canes will minimize pest problems. Thrips and stink bugs can damage some fruit at harvest. Erect varieties have the best disease resistance.

Minimal Inputs Potential: Moderate to high

Blueberry Blueberries require a strict pH range from 4.5 to 5.2 for optimal growth and minimal nutritional problems. Since these soils are generally limited to East Texas, these plants can be grown in containers which have an amended soil. Good sanitation, complete weed control and proper irrigation and drainage are essential for good production. Salt, particularly sodium, is detrimental. There are some pests, but they usually do not have a significant impact. prompt removal of old canes tends to reduce pest problems.

Minimal Inputs Potential: Moderate to high.

Citrus Cold is naturally the limiting factor to citrus production. Adverse soil pH effects can be overcome with sour orange rootstock. Foot rot is easily precluded by high budding and proper planting in well-drained sites. Virus diseases have been excluded to date in Texas by quarantines against citrus plant materials from other areas. Sucking insects, mites, and scale can limit production.

Minimal Inputs Potential: High

Fig Closed-eye varieties, along with early harvest, eliminate the souring caused by the dried fruit beetle. Bird predation of maturing fruit can be extensive. Fig leaf rust can cause extensive defoliation in late summer, particularly in humid areas.

Minimal Inputs Potential: High to Very high.

Grape, Muscadine Muscadine grapes prefer acidic soils. There are few pests or diseases that are limiting, although black rot can cause crop damage.

Minimal Inputs Potential: High to Very high.

Grape, Mustang There are no major limiting problems to the production of this Texas native wild grape. Grape leaffolder can cause extensive defoliation in some seasons, but is rarely debilitating to the vine.

Minimal Inputs Potential: Very high.

Grape, Varietal American types are fairly resistant to serious diseases; grape leaffolder can be damaging in some seasons.

Minimal Inputs Potential: High

Guava There are no limiting problems in adapted climates of South Texas.

Minimal Inputs Potential: Very high.

Jujube There are no limiting pest or disease problems of jujube in Texas. Rootsprouts are extensive.

Minimal Inputs Potential: Very high.

Mayhaw Mayhaw is subject to many of the same pests that attack other pome fruits, but none are considered seriously limiting to production. Both quince rust and hawthorne rust can be severe, but removal of alternate, evergreen hosts should reduce the problem.

Minimal Inputs Potential: High to very high.

Mulberry Bird predation of mature fruit and Cercospora leaf spot are the only serious problems affecting mulberry.

Minimal Inputs Potential: Very high.

Pear Fire blight is a major limitation to susceptible varieties so only resistant varieties should be planted. Codling moth can be serious in North Texas, as can various scale insects, in some seasons.

Minimal Inputs potential: High.

Pecan, Native The same problems that affect improved pecan also affect native pecan although native pecan has generally better scab resistance and can obtain some zinc nutrition from the soil. Pecan weevil is probably the most damaging insect, but its cycle generally corresponds well with the alternate bearing tendencies of native pecan trees. There are several weevil free areas in Texas.

Minimal Inputs Potential: Moderate to high.

Persimmon Both native and Japanese persimmons are virtually free of pest and disease problems. Scale insects may pose occasional problems.

Minimal Inputs Potential: Very High.

Pomegranate There are essentially no limiting pests or diseases, although fruit spots can be serious in humid areas. Fruit spitting near maturity occurs because of poor water relations. Plants tolerate alkaline and somewhat saline soils quite well.

Minimal Inputs potential: Very high.

Strawberry A number of foliar diseases affect strawberry plants, but do not normally achieve great significance. Root diseases are avoided by the use of resistant varieties. Fruit rot, particularly gray mold, can be serious, but incidence is reduced by sanitation and wider plant spacing. Various insects, especially strawberry weevil, can become damaging in some seasons, but most are of only minor significance.

Minimal Inputs Potential: Moderate to high.

Each fruit's rating refers only to the relative ease of production using the least amount of inputs - and then only in those areas where the particular plant is adapted.


Hypertext markup by Gretchen Eagle and Dan Lineberger. http://aggie-horticulture.tamu.edu/archives/parsons/publications/miniput.html