KEEPING YOUR PLANTS HEALTHY
In the small greenhouse the loss of a few plants means a decrease in profit. Proper ventilating, heating, watering, and fertilizing for the type of plants you grow are your best safeguards against trouble. Sterilized soil is important, too. Plants growing in a cold or cool house are less susceptible to pest and disease than those in a warm house. Just remember the old saying about an ounce of prevention. Keep your greenhouse and the surrounding area free of weeds; they often harbor insects. The best way to fight trouble is to avoid it.
When reading the following, always make sure you handle chemicals carefully and read any health and safety notices on the products, before you use them.
Products to Help You
Hundreds of insecticides and fungicides are on the market. Compare labels carefully. Then if you still are in doubt as to which product is best for eradicating an insect or a disease, consult your county agricultural extension agent. If there's anything he doesn't know, he can consult the state university. My own greenhouse medicine chest (which seems amply stocked for any emergency) contains the following items:1. Sodium selenate in powder and capsule form for use against cyclamen mites. (This chemical is poisonous and some growers prefer a slower-acting though less poisonous insecticide, like Endrin.)
2. V-13 Nemacide, a preventative and annihilating soil
treatment for nematodes.
3. Malathion, a general all-round insecticide. (Lindane, is
good for controlling insects invading the green parts of a plant;
chlordane and DDT for eradicating soil-borne insects.)
4. Aramite (or Ovotran) for red spider.
5. Dithion for the brown scale on citrus plants, ivy, philodendron, and amaryllids. If you find a few scales on a plant or two, wash leaves in a strong soap-and-water solution. If you find scales on a number of plants, spray with Dithion or malathion.
6. Snarol for destroying slugs (or use Chlordane).
7. Fermate is my choice for a fungicide.
8. Carco-X, a combination fungicide and insecticide, I find especially good for treating soil for bulbous plants.
9. Sulphur as spray or dust is useful in controlling fungi or mildew.
Most insecticides are poisonous. Handle them with care. Use rubber gloves when spraying the greenhouse.
After you use the sprayer, rinse it out. Store insecticide containers out of reach of pets and children.
Schedule of Pest and Disease Control
Every 10 days, I give my greenhouse a regular all over spraying with an electric Devilbus sprayer. I also have a lightweight, inexpensive plastic sprayer. This holds about a quart of liquid, and can be operated with one hand. I keep it filled with malathion solution for quick dealing with aphids, caterpillars, and thrips. The tank-type sprayer, used in outdoor gardening, is also effective in the greenhouse. This is a cylinder with a hand-pressure pump. It has a strap to slip over your shoulder. It holds about 2 gallons.Insects attack plants in different ways. Thrips scrape away the green tissue from petals, leaving tiny scars. Malathion applied at 5- to 7-day intervals will kill thrips—adults and off¬spring. Spider mites (red spider) cause yellow-and-brown areas on foliage. A spray of cold water is effective if your plants can stand it (African violets cannot). Otherwise, use Aramite spray one week, malathion the next.
Cyclamen mites twist and gnarl the center leaves of many plants. Remove infested plants from the greenhouse; if you must save them, cut out the affected areas, treat the soil with sodium selenate (in solution or capsules) or Endrin, and keep these plants away from the others until they show clean new center growth, a matter of 2 to 4 weeks.
Mealy bugs look like flecks of cotton. When you find only a few on a plant, touch them with a cotton swab dipped in alcohol. For heavy attacks, use a malathion spray.
Get rid of caterpillars and grasshoppers by spraying with malathion or a similar product.
You can clean up brown scale with Dithion or soap and water. The scales are slow-moving bugs and when young are light yellow. While they usually attack only smooth leaves, they will invade an overcrowded batch of hairy-leaved plants, such as episcias. When this happens, use the hand spray, making certain that tops and bottoms and all parts of the rough-textured leaf surfaces are reached.
Fungus attacks show up in blackened buds and rotting stems and leaves. Many plants respond well when the affected parts are cut away and powdered Fermate is applied, or when soil and plants are moistened with Carco-X or some other excellent fungicide.
Nematodes betray their presence in various ways. Plants may have a stunted or wilted look, or there may be blisters on petioles and nodules on the roots. Until recently plants infested with root nematodes had to be disposed of, but V-13 and other soil sterilants and fumigants have proved effective against these pests. Since these products are poisonous, take care to use exactly as directed.
