WHATS BUGGING YOU? How to kill, destroy, expunge, obliterate houseplant pests Diane Martin Harrowsmith Country Life, December 1993 Most Garneners realize that all manner of bugs are a fundamental part of nature--as pollinators, recyclers and sources of food for other animals--and strive for a mutually beneficial coexistence with them. Yet many of today's safe pest-management practices aren't suited for the indoor garden. Few of us are eager to introduce a swarm of green lacewings into our living rooms or to cover our African violets with lloating row covers. Indoors, we need to kill pests dead (to borrow the slogan created by the poet e.e. cummings for Raid pesticides). But we also want to get rid ofthem without harming ourselves, our pets, our plants or the environment. Fortunately, there are better and safer ways than using pesticides, synthetic or natural, to eliminate bugs on indoor plants (see the charts on pages 74 and 75). Although climatic conditions are ideal, food is abundant and there are no natural enemies, indoor bugs are at a disadvantage if you know what you're doing and, just as important, you know what they're doing. The earlier you notice bugs on your plants and take care of them, the better your chances of never being tempted to resort to chemical warfare. What to look for? Foliage wilt and yellowing, leaf drop and stunted growth (which can also indicate improper environmental conditions) are indicators of pest-infected plants. Other signals of insect problems are sticky foliage and foliage that is flecked, blotched, stippled or covered with bumps. Check carefully, for sooner or later everyone encounters one or more of the five most common houseplant pests: mealybugs, whiteflies, scale, aphids and spider mites. MEALYBUGS Mealybugs, which prefer to feast on soft-stemmed or succulent plants and thrive in warmth and humidity, are easy to identify. Their round, white, furry bodies are about the size of a dill seed and are covered with a fine granular excretion, or wax, that makes them look as if they were dusted with flour. They can be found at rest or crawling along stems, on upper as well as lower leaf surfaces (especially along the veins) and in the axils, where leaves and stems meet. They also hide in the tips of new shoots and often cluster together. The citrus mealybug (Plarlococcus citri) is the most common indoor pest, but there are hundreds of types. Because mealybugs are soft-bodied insects, they are highly sensitive to temperature and humidity. Females lay between 300 and 600 eggs in conspicuous cottony masses in protected spots, such as in the angles of stems or midribs of leaves. The eggs hatch in a week's time, and the emerging nymphs begin feeding almost immediately on plant sap. Male nymphs pass through a cocoon stage and emerge with wings and no mouth, dying soon after they mate. After molting several times, females reach maturity, lay eggs for a week or two and then die. It is the nymphs and adult females that cause most damage to plants, by piercing leaves, sucking sap and excreting honeydew (a sticky substance that coats leaves and nourishes black sooty mold, a fungus). Nymphs and adult females are also the most vulnerable, since in these stages they are slow-moving and visible. Likely victims: African violets, aralias, begonias, cacti and other succulents, dieffenbachias, dracaenas, ferns, gardenias, grape ivies, jade plants, philodendrons, pothos. WHITEFLIES Adult whiteiflies, which are unrelated to houseflies, are about the size of a celery seed, have four broadly rounded wings and are covered with a snow-white waxy powder that causes them to resemble tiny moths. They congregate on the undersides of leaves and, when disturbed, fly short distances, creating small, agitated white clouds. The subtropical greenhouse whitelly (Trialeurodes vaporariorum) is the most common indoor variety. Like the mealybug, it is a sucking insect. Most whiteflies are primarily parthenogenetic, which means they can produce off spring without mating. Females lay between 200 and 400 pale green eggs during their lifetime, leaving them in circular clusters on the undersides of leaves. Minute six-legged crawlers--flat and colored light green--hatch in about 10 days. The crawlers attach themselves to the leaves and begin sucking sap and excreting honeydew, which can foster sooty mold. They will remain attached to the foliage while they pass through several scalelike stages from which they emerge as winged adults. Adults, which are easily visible, tend to cluster at the tops of plants and on new growth, especially on shoots that are yellow-green, a color that attracts the insect. Likely victims: Begonias, coleus, fuchsias, hibiscus, peace lilies, pelargoniums, primulas, poinsettias. SCALE There are more than 2,000 species of scale insects; those that attack houseplants are classified either as soft (Coccidae) or armored (Diaspididae) scales. Among soft scales are the types most commonly found on houseplants: hemispherical scale (Saissetia coffeae), black scale (S. oleae) and brown soft scale (Coccus hesperidum). These foes, which are recognizable by their hard, turtlelike, gray-brown shells, are oval shaped and measure between 1/5 and l/4 inch long. Looking like dark bumps on leaves and stems, soft scales are sucking insects. They secrete honeydew and flourish and multiply best in warm, hurnid conditions. Females lay 500 to 1,000 eggs under their shells. When the eggs hatch, the young feed on the mother's body until they are ready to venture out and begin sucking sap from the plant. Female offspring shed their shells twice on their way to maturity, keeping the same form, but males undergo metamorphosls, turning into small, mouthless, flylike bugs. The males live only three or four days--long enough to mate--while females can live for almost four months. Armored scale species are also covered with hard protective shells, which are separate from their bodies, but they rarely produce honeydew. Oysterlike or volcanic in shape, they blend in color with their host plant. Determining whether your poinsettia is covered with a soft or armored scale is important only if you're using biological controls. Deciding whether you have scales or simply bumps on the leaves is more important. Scrape the spot in question with a knife: if it is a scale, it will lift easily. Likely victims: Citrus, cyclamens, ivies, palms, philodendrons, poinsettias, schefleras, weeping figs. APHIDS Sometimes called plant lice or green flies, aphids are a huge genus--about 4,000 species--though they are more common in greenhouses than in living rooms. Even better, only a small percentage of aphids, approximately 10 percent, attack many different plants; most aphids feed only on a particular species. Still, there are plenty of aphids to torment the indoor gardener: fern aphids (Idiopterus nephrolepdis) attack ferns; melon aphids (Aphis gossypii) attack dioscorea and schefflera; mottled arum aphids (Macrosiphum circumflexum) attack amaryllis, arums, begonias, caladiums and cyclamen. The type most commonly encountered on houseplants is the green peach aphid (Myzus persicae), which is also a threat to many agricultural crops. Aphids' soft, delicate, pear-shaped bodies are about the size of sesame seeds and are colored pink, white or yellowish green. Equipped with long legs, antennae and a set of tailpipelike projections off their backs, most aphids are wingless and slow moving indoors. They feed on succulent growth, causing wilting and deformed leaves and buds, and they secrete honeydew; its shine may be one of the first signs that your plants are infested. Although aphid reproduction is a complicated affair--some females lay eggs, some give birth to live young, some do both--indoors, aphids usuallv reproduce parthenogenetically and give birth to live young rather than laying eggs. That's one reason why they can turn up so quickly on a leaf that appeared to be aphid-free the day before. Because the offspring stay close to their mothers, aphids are found in clusters on new growth, flower buds and the undersides of leaves. Each unfertilized female produces about 50 daughters that mature in approximately a week, ready to become mothers themselves. Likely victims: African violets, arrowhead vines, begonias, caladiums, cinerarias, chrysanthemums, cyclamens, ferns, gardenias, hibiscus, ivies. SPIDER MITES The first sign of spider mites is usually stippled, yellowing leaves, the result of the tiny punctures these pests make in order to suck sap from the plant. Spider mites also spin irregular webs that, in time, can encase an entire plant. Although related, these are not the beneficial predatory mites that eat other insects; these mites eat your plants. The two-spotted spider mite (Tetranychus bimaculatus) is the species found most commonly on indoor plants. Similarly troublesome, especially on cyclamens, begonias, grape ivies and African violets, are broad or cyclamen mites (Steneotarsonemus pallidus), which are much smaller than spider mites, about one-fourth their size. Citrus red mites, false spider mites and European red mites also ravage houseplants. With a 10-power hand lens, you can identify spider mites: greenish, pinkish or yellowish elliptical forms with eight legs and two large blotches on either side of their backs. The female lays between two and six round, shiny, cream-colored eggs each day. The six-legged baby mites feed for a daY or two after hatching, then begin a series of molts until they reach maturity (8 to 20 days). Outdoors, twospotted spider mites go through diapause, a resting phase somewhat like hibernation, but indoors they are active throughout the year. True spider mites live in colonies, clustering on mature leaves, and they prefer dry, warm conditions, exactly the environment provided by many houses. Misting plants daily or hosing frequently with a jet of water will break up webs, wash away eggs and suppress their development. Likely victims: Aralias, aspidistras, crotons, dracaenas, ferns, ficus, hibiscus, ivies, palms, scheffleras. Diane Martin lives in upstate New York. This article was adaptedfrom Kill Bugs Dead: An Indoor Gardener's Guide to Eliminating Insects on House Plants Without Using Harrnful Pesticides (The Scriptorium Press, 1992). THE WEAPONS OIL-DETERGENTSOLUTION 1 cup vegetable oil 1 Tbsp. dishwashing detergent Mix well. To use, dilute as follows: 1 to 2 l/2 tsp. oil-detergent solution 1 cup warm water. Spray plant thoroughly and let sit for 1 to 2 hours, then rinse with clear, warm water. TOBACCO TEA 1 cigarette or 1 cigar butt or 1 tsp. pipe tobacco 1 cup warm water 1/4 tsp. olive oil 1/4 tsp. liquid soap Soak tobacco in water for 24 hours.Strain and discard tobacco. Combine tobacco water, olive oil and soap, and mix well . To use, spray on affected area of plant and let sit for several hours. Rinse with warm water. INSECTICIDAL SOAPS Insecticidal soaps are commercial preparations based on soaps made from fatty acids. They are effective only when wet and in direct contact with the bug. Relatively harmless, they still should be used in careful compliance with label instructions.