Unlike many garden plants, orchids have few native pests. The high altitudes at which most orchids grow, their preference for living in trees, and their usually leathery leaves and thick stems make them an undesirable diet for predatory insects. Only two native pests, the cattleya fly and the orchid weevil, may become dangerous, but they are largely limited to a few areas on the East Coast and the San Francisco Bay region.

However, orchids in culture have been attacked by some of our home-grown garden pests—scale, aphids, and others of their ilk. Most of the time these common pests are negligible. Yet a single snail, slug, or cockroach can do grave damage in a few hours. Your battle with them can be long and deadly. Slugs, particularly, have developed persistent and voracious appetites for tender new orchid shoots, buds, and flowers.

The wisest approach to the control of orchid pests is to remember that if your orchids are attacked by insects it will be primarily your fault. Too much water, poor drainage, or not enough ventilation are cultural evils which will weaken orchids and make them easy prey for pests. Cleanliness, you might say, is next to "orchidliness." Keep your plants and their surroundings clean and you will have little or no insect trouble. Scum or algae accumulations on pots are breeding places for minute pests. Pick up refuse, paper, and leaves left near the plants. Insects don't like to crawl across gravel or cinders, and a bit of paper or a leaf makes their journey to your plants much easier.

Keep ants away from orchids! Ants carry aphids, mealy bugs, and scale. No ants, no pests, is the rule to be followed here. Buy a suitable ant poison. Keep some in the orchid window or case; put more in the kitchen, where ants tend to congregate, and more outdoors where they come from. Stop them before they reach your orchid collection. This may sometimes be a bit difficult unless you isolate orchids over saucers of water, or isolate orchid benches from floors and walls. While in bud and flower, orchids secrete a sweet honey that ants find irresistible. The honey forms in drops at the base of the flower. Taste it; you'll be amazed how good it is.

If you do get scale or aphids on your plants, the cure is simple if you act in time. Never put off combating pests until tomorrow. They multiply so fast that what would be a few moments' work today will take hours later on. Aphids can be brushed off with a moist soft cloth, or killed with a nicotine spray. Scale succumbs to the same treatment. If the scale infestation is unusually heavy, dip a soft toothbrush into the nicotine solution and scrub the plants. Get down into the nooks and crannies at the base of the rhizome. That's where scale breeds, gathering strength for a sudden eruption up the stem.

Thrips and red spider aren't much of a problem—if the cultural conditions under which your orchids are grown are correct. You may not see them—they are very small. Their presence is indicated by the damage they do: many minute white scarlike marks on the underside of leaves, buds, and flowers. Thrips like dry, hot conditions, not the moist atmosphere which orchids require. When you have thrips, merely increase your humidity. If they don't leave fast enough to suit you, spray them with a nicotine solution. The same remedy is good for red spider, although a gentle spray of water often will knock them off the foliage. Once off the plant, they usually don't get back.

ORCHID PESTS

Top: Sow Bug; Red Spider; Cockroach; Scale

Center: Thrip; Mealy Bug; Dendrobium Beetle; Aphids

Bottom: Snail; Slug; Cattleya Fly; Orchid Weevil

Mealy bug infestations on the more tender and succulent types of orchids may become serious. Luckily the colonies spread rather slowly and are usually noticed in time to stop them. They hide beneath the rhizomes, under the leaves, and in the axils of leaves and stems. A toothbrush scrubbing with nicotine or a thorough spraying which forces the nicotine into the sheltered areas and under the dead tissues will stop mealy bugs cold.

A word of warning at this point. When using nicotine sprays, and they are the most widely used for orchids, never let the spray get on flowers and buds. Both water and the chemical will spot them badly, ruining them for further decorative use. Nothing has been said as yet about oil sprays which, unfortunately, are somewhat dangerous to use and have not been adapted widely to orchids. The difficulty lies in the oil that is used. Mineral oils—those from petroleum products—in concentrations heavy enough to stop pests, particularly scale, clog the stomata of orchids and the plants may eventually die. On the other hand, insecticides using a vegetable oil base have proved of considerable value.

The truly serious pests, however, are slugs, snails, cockroaches, and sow bugs. The damage they can do is tremendous. One baby slug can cut down a small shoot, demolish a bud, or eat the heart out of a flower in one night. With these insect foragers the rule is watchfulness and prevention. There is no cure for the damage they do. Once new growth is topped, it probably won't develop; if it does, it probably won't bloom. Once a flower is ruined, you might as well throw it away.

Scatter a metaldehyde snail poison near your orchids. Slugs and snails will always stop for a taste and then die before they can reach the orchids. You can't do much about sow bugs except pick them off the compost when you see them. Some of the Paris green baits are effective, but they are also poisonous to children and animals. Cockroaches can be controlled by a little roach poison scattered in odd corners.

It is a wise precaution in outdoor or window culture to tie a bit of cotton—about an inch or two thick and wide— around the base of new flower stems. For some reason slugs and snails won't crawl over the cotton to get to the flower bud. Even sow bugs and cockroaches are reluctant about crossing such a barrier. In tying the cotton barrier, keep it a fraction of an inch above the top of the compost. Nonabsorbent cotton, if it can be secured, is the best. However, if you have isolated benches and practice cleanliness, cotton on orchid flower stems is a confession of laziness.

The chances are better than a hundred to one that you will never be bothered by the cattleya fly, the dendrobium beetle larva, and the orchid weevil. They do serious damage, though, in some areas of the United States where large commercial orchid collections are maintained. Cattleya flies and dendrobium beetle larvae bury themselves inside orchid stems. You can detect them by blackened spots on the pseudobulbs. About the only cure is to dig them out and destroy them individually. The injured tissues are dusted with sulfur to protect them against rot. Before you start cutting up an orchid, have it checked by an expert. All black spots aren't caused by larvae.

If you get any of the native orchid pests, the orchid weevil is the most likely invader. It is a small, black, shiny beetle which feeds lightly on buds and flowers. Its depredations are not extensive, but it causes the flowers to become spotted and unsightly. It lives in the osmunda when not out to dinner, and the job of killing it is not an easy one. Paradichlorobenzine—the same insecticide used on lawn web worms—is the standard control for the weevil. Go after them on a warm morning when the temperature is 85° or better. Sprinkle a half-teaspoon of paradichlorobenzine crystals over the compost of each five-inch pot— less on smaller pots. Don't let the crystals touch and burn the leaves. Place the treated pots in a closed Wardian case, blocked-off window, or closed greenhouse for the rest of the day. If the temperature goes up to 1000 or more, don't worry. The warmth makes the crystals evaporate, forming a heavy gas that seeps down through the compost with a killing intensity. Be certain that the pots are dry before you begin treating your plants, and wait a day or two afterward before watering again.

Recently, excellent control of the orchid weevil has been secured by weekly dusting or spraying with pyre-thrum and derris combination insecticides. So far, DDT has been highly variable. Only about half the preliminary reports are favorable. The standard 5 per cent and 10 per cent concentrations of DDT apparently injure orchids. However, 2 per cent or 3 per cent concentrations may kill all orchid pests without undue injury to orchid foliage.

Here is one of the finest DDT formulas to come out of experimental tests. It is used by an eastern grower who maintains that it is good for all orchid pests; even slugs and cockroaches succumb. Mix two ounces of du Pont's Deenate 25-W with one gallon of water and add two teaspoons of Rohm Sc Haas D-195 soap spreader. This is the stock solution. Store it in a cool, dark place. It should remain active for many months. When ready to spray mix the stock solution with four gallons of water, pour into a spray gun and cover your plants well with a gentle, fine mist of the dilution. The residue on the plant remains effective for several months. It will control scale, though it may not get into nooks and crannies where scale hides. A good scrubbing with the mixture at potting time is the best precaution. Be careful when handling DDT not to get it on your skin, it may be injurious. In any event, a good practice is always to wash yourself with a strong soap after applying DDT to plants.

Bacterial rots are the inevitable result of poor culture. They are caused by a cold, damp atmosphere around the orchids. Wet rots, caused by cold water dripping from glass panes onto the plants, start out as a dark-brown discoloration on leaves. Soon the infected areas become black and water-soaked. Dry rots are caused by the same cold, damp conditions. But instead of developing soft, watery tissues, the affected areas become dry, hard, and filled with woody fibers. The treatment for both is identical: cut out the infection, dust with sulfur, and improve your culture.

Beginners often run into a third type of rot. Minimizing the importance of well-drained composts, they use heavy soils. Water left standing on top of the compost—not quickly draining off—will rot orchid rhizomes. The base of orchid pseudobulbs becomes semitransparent, gradually darkens, and the rot spreads through the bulb. The treatment is harsh and the cure uncertain. Lift the plant out of the pot, brush off the compost, cut away the rot, and dust with sulfur. Let the plant dry out for a day or so and repot correctly. Watch for any continued infection; there probably will be some, since the rot travels freely through the tissues.

Always remember that the best you can do is never too much when it comes to pest control. You grow orchids not for their foliage but for their flowers. Similarly, most insects attack orchids for their flowers. You can win the struggle, but you must practice cleanliness, watchfulness, and prevention. Never give a bug a break. Once you have paid as much as $25 for a single plant, and then seen what a slug or snail can do to it, you'll know what we mean!

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