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ENY-330 Houseplant Arthropod Pest Management 1 D. E. Short, S. M. Dickerson, and E. A. Buss2 1. This document is ENY-330 (MG004), one of a series of the Department of Entomology and Nematology, Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida. First printed: October 1993. Revised: October 2006. Please visit the EDIS Website at http://edis.ifas.ufl.edu. 2. D. E. Short, professor Emeritus, S. M. Dickerson, DPM student, and E. A. Buss, assistant professor, Entomology and Nematology Department, Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida, Gainesville, 32611. The use of trade names in this publication is solely for the purpose of providing specific information. UF/IFAS does not guarantee or warranty the products named, and references to them in this publication does not signify our approval to the exclusion of other products of suitable composition. Use pesticides safely. Read and follow directions on the manufacturer's label. The Institute of Food and Agricultural Sciences (IFAS) is an Equal Opportunity Institution authorized to provide research, educational information and other services only to individuals and institutions that function with non-discrimination with respect to race, creed, color, religion, age, disability, sex, sexual orientation, marital status, national origin, political opinions or affiliations. U.S. Department of Agriculture, Cooperative Extension Service, University of Florida, IFAS, Florida A. & M. University Cooperative Extension Program, and Boards of County Commissioners Cooperating. Larry Arrington, Dean Many different plants may be grown indoors for personal enjoyment, including orchids, bromeliads, ivys, spider plants, and many other ornamental and flowering species. It is important to provide appropriate care of indoor houseplants, such as described in Care of Plants in the Home (Cir 454). However, sometimes insects or their relatives can become a problem. This publication describes some of the most common pests, their damage, and several control options for non-commercial plant health care. Common Pests of House Plants Spider mites (Figure 1) are less than 1/32 inch long and may be greenish, yellowish, reddish, or virtually colorless. Mites suck juices from plants through their needle-like mouthparts causing a speckled appearance called stippling. They are usually found on the underside of leaves. When plants are heavily infested, fine webbing may be seen on the plant. A hand-held lens or magnifying glass is helpful in detecting spider mites before severe damage occurs. Figure 1. Red spider mites and their webbing. Credits: James L. Castner, University of Florida Aphids (Figure 2) are soft-bodied, pear-shaped, have long antennae, and two short tubes or cornicles at the rear end of the body. They are usually less than 1/8 inch long and may or may not have wings. Aphids, which usually feed in colonies, may be green, pink, black, brown, or yellow in color. They tend to suck fluids from new, rapidly growing plant tissue. In heavy infestations, leaves may wilt or turn yellow and prematurely drop. In some cases, aphid saliva is toxic to the plant and causes new
Houseplant Arthropod Pest Management 2 growth to curl and become distorted. Some aphids also transmit plant viruses, and most secrete honeydew, which is a sugary waste product. Sooty mold is a fungus that grows on honeydew, and may affect plant growth. It may also be present with infestations of other honeydew producing pests, such as mealybugs, soft scales and whiteflies. Figure 2. Crape myrtle aphids. Credits: James L. Castner, University of Florida Mealybugs (Figure 3) are soft-bodied insects covered with a white powdery material. Some species have long waxy filaments extending from the rear of the body. When mature they are about 1/8 inch in length. They damage plants by sucking fluids from leaves, stems, or roots, but may also inject toxins into the plant. Leaf yellowing and reduced plant growth are common symptoms of mealybug feeding. Figure 3. Grape mealybug on Ixora. Credits: Lyle J. Buss, University of Florida Scale insects secrete a waxy protective covering over their bodies and are known as either soft or armored scales. The covering that is produced by soft scales is attached to their bodies. The covering secreted by armored scales is not attached to the body. Scales (Figure 4) can be almost any color depending on the species, and may be circular, oval, oblong or pear-shaped. They are 1/8 to 1/3 inch long when mature. They may be found on either side of leaves, on branches or stems. Some scales also infest stem crevices, axils of the leaves, or roots, making them hard to control. Scales cause damage by sucking plant juices. Reduced growth and premature leaf drop may occur, as well as yellow spots on tops of leaves from scales feeding on bottoms of leaves. Figure 4. Barnacle scales. Credits: Lyle J. Buss, University of Florida Adult whiteflies (Figure 5) are white and resemble tiny moths that swarm about the plant when disturbed. Nymphs (immatures) are pale green, flat, and oval-shaped, making them hard to see. Both adults and nymphs are about 1/16 inch long and tend to gather on the undersides of leaves where they suck plant juices. Whitefly feeding generally causes plants to become unthrifty. Whiteflies are capable of transmitting viruses to some plants. Figure 5. Silverleaf whitefly adults. Credits: James L. Castner, University of Florida
Houseplant Arthropod Pest Management 3 Thrips (Figure 6) are small insects that are black or yellow-brown, may or may not have wings, and jump when they are disturbed. They range from 1/16 to 1/8 inch in length. They usually feed on plant flowers and leaves. They do this by punching a hole in the plant with a mandible and inserting a straw-like structure in the wound to extract plant juices. Leaves may take on a silvery appearance or become deformed, while spots or blotches form on flowers. Thrips may also transmit viruses to plants. Figure 6. Eastern flower thrips. Fungus gnat maggots are white, worm-like larvae that are about 1/4 inch long when mature. They feed on decaying matter and fine root systems in soil. Wilting or an unhealthy appearance of the plant may become evident during a heavy infestation. Adult fungus gnats (Figure 7) may be seen crawling on the soil surface or flying around windows before severe plant damage occurs. Figure 7. Fungus gnat adult. Credits: James L. Castner, University of Florida Springtails (Figure 8) are attracted to moist soil, but rarely cause damage to plants. They may be a nuisance if many are present. Springtails range in size from microscopic to less than 1/4 inch long, are usually white or brown in color, and jump when disturbed. Figure 8. Springtail. Control Measures Any plant with an insect problem should be separated from other plants immediately. Many cultural practices are effective in managing houseplant pests and may be sufficient unless the outbreak is severe and affects many plants. All of the pests may not be immediately eliminated. Insects hidden in leaf axils or under leaves, and any eggs present are likely to survive initial cultural changes. If the problem continues, a pesticide may be needed. If the infested plant's value does not warrant the cost of chemical treatment, dispose of the plant and its soil and sanitize the area. Cultural Practices Exclusion Any plant purchased should be carefully examined for pests. It is a good idea to isolate new plants for a while before placing them with other plants. This will prevent the spread of any infestations that may develop if eggs were present at the time of purchase. Sanitation Sterilized soil should always be used for potting to help prevent damage from soil-born root pests. Washing or Spraying with Water Washing with soapy water and a soft brush or cloth will remove aphids, mealybugs, and scale insects from broad-leaved plants. Use 1-2 tablespoons of a mild dishwashing liquid to a gallon of water. Do not use laundry detergent or automatic dishwashing detergent. Large plants that are difficult to move can be cleaned with a sponge or a toothbrush. Routinely wash plants twice per year or every 7 to 14 days during a pest outbreak.
Houseplant Arthropod Pest Management 4 Spraying plants with a forceful stream of water will remove many insects. Be sure to spray the undersides of leaves where most plant pests are found. Spraying also keeps the foliage free from dust and the plants look more attractive. Unfortunately, this tactic may not kill some insects, and they could crawl back on. Handpicking If one or a few plants are involved, you may be able to control aphids and mealybugs by removing them with a toothpick or tweezers. Handpicking is not effective against really tiny insects and mites. Alcohol An easy way to control a light infestation of mealybugs or aphids is to wet or remove the insects with a swab or cotton ball that has been dipped in a solution of 1/2 water and 1/2 rubbing alcohol. Be careful not to over apply as this mixture may burn some sensitive plants. Try on a small plant part first. Avoid Over-Watering Fungus gnats and springtails are attracted to warm, moist environments and may be an indication that plants are receiving too much water. Allowing the soil to dry until only slightly moist may eliminate problems with these pests. Over-watering can also contribute to fungal diseases that cause root rot. Poor drainage will contribute to pest problems in the same manner as over-watering. Chemical Control Correct identification of the pest is essential to choosing a pesticide. Some products kill only certain pests, while others act against many pests. Products labeled for houseplant insect control include soaps, oils, and products made from plant extracts. Some insecticides labeled for general household pests (e.g., cockroaches, ants, etc.) contain materials that may kill plants or burn foliage. Be sure to choose a product that is specifically labeled for houseplants. Insecticides are poisons and should be handled as such. Read and understand the manufacturer's label before using the material, and observe all instructions and precautions. Do not exceed the rate indicated on the label. Take plants outside to treat them. Do not spray plants in rooms where fish aquariums, birds, or other pets or people are located. Wear rubber gloves when handling and applying pesticides. Wear a dust mask or avoid breathing mists or fumes. Do not spill sprays on the skin. Change clothes and wash all exposed parts of the body immediately after using pesticides. Store pesticides in original labeled containers in a locked area out of reach of children. Rinse empty containers 3 times, wrap in newspaper, then crush or puncture to prevent re-use. Place the container in the garbage can for disposal in an approved sanitary landfill. Some insecticides and miticides are available in a concentrated form that must be mixed with water, or a ready-to-use sprayable form. The concentrate is more economical, while the ready-mixed spray is more convenient. Both formulations are equally effective if used properly. Some preparations contain several pesticides to provide control against many common insect and mite pests, as well as some fungal diseases. See Table 1 for a list of some products available to homeowners for common pests of houseplants. For More Information Care of Plants in the Home (Cir 454) http://edis.ifas.ufl.edu/MG031 Fungus Gnats (ENY-912) http://edis.ifas.ufl.edu/IG125 Insect Management in the Home Garden (ENY-476) http://edis.ifas.ufl.edu/VH036 Mites (ENY319) http://edis.ifas.ufl.edu/MG001 Scales and Mealybugs (ENY-323) http://edis.ifas.ufl.edu/MG005 Silverleaf Whitefly (ENY-911) http://edis.ifas.ufl.edu/MG362 Thrips on Ornamental Plants (ENY-333) http://edis.ifas.ufl.edu/MG327
Houseplant Arthropod Pest Management 5 Table 1. Some products available to homeowners for the control of insect pests on house plants. Active Ingredient Trade Names Pests Comments Bifenthrin Ortho Rose & Flower Insect Killer Aphids, beetles, caterpillars, fungus gnats, lace bugs, leafhoppers, leafminers, leafrollers, mealybugs, scales (crawlers), spider mites, thrips, whiteflies, others Synthetic pyrethroid Capsaicin Bonide Hot Pepper Wax Concentrate Aphids, lace bugs, leafhoppers, spider mites, thrips, others Insect repellent Horticultural oil Bonide All Seasons Horticultural & Dormant Spray Oil, Sunspray Ultrafine Horticultural Oil Aphids, leafrollers, mealybugs, mites, scales, whiteflies, others Petroleum (Bonide) or Parafin (Sunspray) based oil Imidacloprid Bayer Advanced Garden 2-in-1 Plant Spikes Aphids, leafhoppers, mealybugs, plant bugs, scales, thrips, and whiteflies Fertilizer and insecticide combined Insecticidal soap Bon-Neem Insecticidal Soap, Concern Insecticidal Soap, Safer's Houseplant Insecticidal Soap, Schultz Garden Safe Insecticidal Soap Aphids, mealybugs, scales (crawlers), spider mites, thrips, and whiteflies Made from potassium salts of fatty acids Permethrin Bonide Eight Garden & Home Insect Control, Southern Ag Garden Insect Dust, Spectracide Bug Stop Multipurpose Insect Control Concentrate Aphids, beetles, gnats, leafhoppers, leafminers, leafrollers, mealybugs, scales, spider mites, thrips, whiteflies, others Synthetic pyrethroid Pyrethrins Schultz Expert Gardener Houseplants & Gardens Insect Spray, Schultz Garden Safe Houseplant & Garden Insect Spray, Spectracide Houseplant & Garden Insect Spray Aphids, earwigs, lace bugs, leafhoppers, leafminers, leafrollers, maggots, mealybugs, millipedes, mites, moths, pillbugs, rootworms, thrips, whiteflies, others Made from extracts of chrysanthemum flowers