Even the best indoor gardens can experience an occasional aphid infestation or mealybug outbreak. After all, pests are a natural part of gardening – indoors or out. The ones attacking out in the garden can be bothersome enough, but it’s the houseplant pests that can become the most annoying. After all, how many multi-legged creatures do you normally invite into your home?
Sticky traps are a good choice in indoor gardens. They catch flying and small crawling insects that suck or rasp the stems and leaves of houseplants. Those specific to a particular insect include a pheromone scent attractant tailored to the specific pest.
Photo Credit: ©2002 Dolezal Publishing/John M. Rickard
Insecticidal soaps are effective only if applied directly to the pest. A cotton-tipped applicator can be used to apply the soap to infested areas.
Photo Credit: ©2002 Dolezal Publishing/John M. Rickard
Begonias are frequent hosts to whiteflies.
Photo Credit: ©2002 Dolezal Publishing/John M. Rickard
Mealybugs are covered with a cottony or mealy wax secretion. This frequent houseplant pest sucks sap from plant leaves and produces a sticky residue.
Photo Credit: ©2005 Buglady Consulting
How you handle potential houseplant pest invasions is what makes the difference between a healthy plant and one that might not recover. The key to controlling these invaders is recognizing their various signs and symptoms and then taking quick action before the problem spreads.
Spotting pests on plants really isn’t that difficult if you continually keep your eye out for them. Many can often be found in clusters on leaves or stems, flying around the plant or crawling around the base of it. The following quick reference lists some common houseplant pest symptoms you may notice on your indoor plants, as well as possible causes and remedies.
Symptom: Curled, twisted, sticky leaves; stunted or deformed blooms; loss of vigor.
Cause: Aphids. Look for clusters of 1⁄16-inch, round, soft-bodied insects that vary in color from black, brown, green and yellow to red and even pink. They generally feed on new plant growth, sucking sap out of leaves, causing holes and distorting new growth.
Remedies: Spraying the plant with a stream of water daily for a period of several days greatly reduces aphid populations. Other options include spraying with a solution of 2-3 tablespoons dishwashing liquid per 1 gallon of water or spraying with insecticidal soap.
Symptom: White trails on or inside leaves; papery yellow or brown blotches on foliage.
Cause: Leaf miners. Look for small, pale larvae and 1⁄6-inch, green or black flying insects.
Remedies: Remove infested leaves. Move plant to a sheltered outdoor spot and spray foliage with neem oil extract solution. (Completely read and carefully follow all package instructions exactly when applying any product.)
Symptom: Stunted plants; white cottony clusters in leaf axils.
Cause: Mealybugs. Look for white or gray, 1/8-inch-long bugs covered with a cottony or mealy wax secretion. (They look like tiny cotton balls on plants.) Mealybugs suck sap from plant leaves and produce a sticky residue. They thrive in tight areas on plants such as the joints where leaves attach to the stem. If left unchecked, these houseplant pests can eventually kill a plant.
Remedies: Lift them off with a cotton swab moistened in rubbing alcohol, or spray them with a diluted mixture of rubbing alcohol and water (3:1); spray with insecticidal soap or horticultural oil, carefully reading and following all label instructions.
Symptom: Stunted, discolored, spotted plants with deformed roots, sometimes bearing swollen galls; loss of vigor.
Cause: Nematodes – microscopic, wormlike creatures that live in the soil and feed on plant roots.
Remedies: Repot houseplant into sterile potting soil after rinsing roots in neem oil extract solution and pruning away swollen root nodules. (The plant may require several repottings at monthly intervals.)
Symptom: Leaves speckle, wrinkle, turn yellow and drop; minute white webs on leaf undersides and at foliage junctions.
Cause: Spider mites. Shake foliage and blossoms over white paper, and look for moving red or yellow, spiderlike specks. Spider mites suck leaf cells dry, eventually causing foliage to dry and curl.
Remedies: Spider mites prefer a hot, dry environment, so deter them by misting plants. Regularly cleaning foliage with water and occasional rinsing can also help; spray with insecticidal soap if necessary, carefully reading and following all label instructions.
Symptom: Stunted, yellow plants lacking vigor; leaf drop; sticky secretion on plant.
Cause: Scales. Look for 1⁄20-inch, flylike insects accompanying soft or hard, 1⁄50-inch, mounded bumps on stems and leaves. These smooth, brown, oval pests look like small shiny bumps and can eventually kill a plant. They attach to the undersides of leaves along the midrib or stems.
Remedies: Remove infested foliage, or swab scales with soapy water or a diluted denatured alcohol solution – rinse well after solution dries; can also scrape scale off with a fingernail or by wiping with a damp cloth. If scale insects persist, choose an insecticidal soap or horticultural oil that specifically lists them and your plant, and carefully read and follow all label instructions.
Symptom: Brown-, silver- or white-speckled leaves, possibly gummy or deformed; deformed blooms fail to open.
Cause: Thrips. Shake foliage and blossoms over white paper, and look for moving winged specks. Or, using a hand lens, look for small, long-bodied insects with fringed wings typically on the undersides of leaves. (Also inspect for shiny black spots, which are fecal matter.) Thrips thrive in hot, dry conditions and feed on plant tissue, causing silvering and mottling of stems, foliage and flowers.
Remedies: Increase humidity and watering; remove and destroy infested foliage; spray with stream of water. Soaps and horticultural oil sprays also can be used for large infestations. (Again, carefully read and follow all package directions.)
Symptom: Yellow leaves and stunted, sticky plants; badly infested leaves will drop. When foliage is shaken, a cloud of white insects may fly up.
Cause: Whiteflies. Shake foliage and look for 1⁄20-inch, white, mothlike insects. Inspect leaf undersides for scalelike, gray or yellow eggs. Whiteflies tend to frequent begonias and herbs. Larvae and adults suck plant sap and deposit sticky honeydew.
Remedies: Whiteflies can spread rapidly, so quick detection and treatment are especially important. Remove and destroy infected plant parts immediately and vacuum up whiteflies at night, while they’re resting. Catch with sticky traps. If necessary, use insecticidal soap, following all package instructions. Repeat on a weekly basis until the infestation is under control.
