Insects and Related Pests of House Plants and Their Control 1
D. E. Short 2
Carefully examine any plant you may purchase to be sure they are free of
pests. After bringing the plant home, it is a good idea to isolate new plants
for at least a month before you place them with other plants. During this
time, you can watch the new plants and discover any infestations that develop.
Always use sterilized soil for potting to help prevent infestations of soil
pests such as nematodes, springtails, psocids, and fungus gnats.
Pests of House Plants
Mealybugs and spider mites are the most common pests on house plants.
Mealybugs are soft-bodied insects covered with a white powdery material. When
mature they are about 1/8" in length and some species have long wax
filaments extending from the rear of the body. They damage plants by sucking
the plant juices.
Spider mites are about 1/50" long when mature and may be
greenish, yellowish, reddish or virtually colorless. They are commonly found
on the underside of the leaves. When plants are heavily infested, fine webbing
will be noticed on the plant. Mites suck juices from plants through their
needlelike mouthparts. A 10- or 15-power magnifying glass is very helpful to
detect infestations before severe damage occurs.
Aphids may be green, pink, black, brown, yellow or blue in color.
They are usually less than 1/8" long and may or may not have wings. They
are pear-shaped and have long antennae and two short cornicles or tubes
extending from the rear end of the body. Aphids suck plant juices and cause
new growth to curl and become distorted.
Scales can be almost any color depending on the species. They are
1/8 to 1/3" long when mature, surrounded with a waxy covering and may be
circular, oval, oblong or pear-shaped. Scales are found on both sides of the
leaves as well as on twigs and branches. They may be almost hidden in the
crevices of the stem or axils of the leaves. Scales cause damage by sucking
plant juices.
Whitefly adults are about 1/16" long, white in color, and
resemble tiny moths. When disturbed they will swarm about the plant. The
nymphs (immatures) are 1/16" in length, pale green in color, flat, and
oval shaped. They are found on the underside of the leaves and cause damage by
sucking plant juices.
Fungus gnat maggots, Springtails and Psocids are soil pests that may
damage the root systems of house plants. Fungus gnat maggots are white,
worm-like in shape and about ¼" long when mature. Springtails range in
size from microscopic to about 1/5" long, are usually white in color, and
jump when disturbed.
Psocids range in size from about 1/32 to 1/16" in length, and
usually white to gray colored, and may or may not have wings.
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Control Measures
Syringing - Spraying plants with a forceful stream of room temperature
water once every two weeks will remove many insects before they have a chance
to become established. Be sure to spray the undersides where most plant pests
are found. This is best done outdoors or in a laundry sink. Spraying also
keeps the foliage free from dust and the plants looking more attractive. Give
your plants a shower twice a month.
Washing - Washing with soapy water and a soft brush or cloth may be
all that is needed to remove aphids, mealybugs, and scale insects from
broad-leaved plants. Use 2 tablespoons of a mild dishwashing liquid to a
gallon of water. Large plants that are difficult to move can be cleaned with a
sponge or a toothbrush. Give your plant a thorough washing twice a year. For
persistent scale problems scrub leaves gently with a soft brush.
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.
Caterpillars may be picked off plants by hand and destroyed. Cutworms, slugs,
and snails may be found in their hiding places during the daytime and
destroyed or picked from the plants at night when they come out to feed.
Alcohol - An easy way to control a light infestation of mealybugs or
aphids is to wet or remove the insects with a swab that has been dipped in a
solution of 1/2 water and 1/2 rubbing alcohol. Swabs recommended for babies
are excellent. Be careful not to over apply as this mixture may burn some
sensitive plants.
Nicotine Compounds - Aphids may be controlled by using home-made
nicotine preparations. Soak cigar or pipe tobacco in water for several days
and dilute to the color of weak tea before adding 2 teaspoons of a mild
detergent to a gallon of nicotine solution.
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Chemical Controls
The concentrated form of insecticides and miticides may be purchased at garden
supply or similar stores, and should be mixed with water prior to spraying.
For control of mites, aphids, mealybugs, whiteflies, and thrips a commercial
insecticidal soap may be used. If a commercial soap is not available, 1 1/2
teaspoons of dishwashing liquid per quart of water may be substituted. Do not
use dishwashing liquids containing a degreaser and do not use an automatic
dishwashing soap or detergetnt. Repeat in one week and later as required.
Complete coverage of the plant, especially the underside of the leaf, is
important. For scale control, a commercial horticultural oil may be used. If a
commercial oil is not available, substitute 1 1/2 teaspoons dishwashing liquid
and 1 1/2 teaspoons vegetable cooking oil per quart of water. Repeat in 10
days and later as required. Application to house plants is probably best made
with a hand atomizer sprayer. The type which holds one pint to one quart of
spray is suitable for most homes and small greenhouses.
For control of soil-inhabiting pests such as fungus gnats, springtails, and
psocids, soak the soil with diazinon solution mixed at the rate of 1 teaspoon
25% diazinon emulsifiable concentrate per gallon of water. Take plants
outdoors, place under shade and treat. Return inside when foliage is dry.
Ready-to-use spray preparations are available wherever houseplant products
are sold. Read the label on the container to be sure that it can be used
safely on plants. Some insecticide sprays in aerosol or trigger spray
containers have oils or other materials that will kill plants or burn foliage.
Commercial preparations that contain several pesticides to provide control
against a broad spectrum of common plant pests including spider mites, scales,
aphids, whiteflies, mealybugs and fungal diseases may also be purchased. Read
the label and follow the directions on the container.
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Precautions
Insecticides are poisons and should be handled as such. Read the
manufacturer's label carefully before opening the container and observe all
instructions and precautions. Do not spray plants in rooms where fish
aquariums, birds, or other pets are located. Wear rubber gloves when handling
and applying insecticides. Avoid breathing mists or fumes. Do not spill sprays
on the skin. Change clothes and wash allexposed 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 and put rinsings
in spray tank. Dispose of empty containers (one gallon or smaller) by wrapping
in newspaper, crush or puncture to prevent re-use, and put in the garbage can
for disposal in an approved sanitary land fill.
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Footnotes
1. This document is ENY-330, one of a
series of the Department of Entomology and Nematology, Florida Cooperative
Extension Service, Institute of Food and Agricultural Sciences, University of
Florida. Date first printed October 1993, Revised April 1996, April 1997.
Please visit the FAIRS Website at http://hammock.ifas.ufl.edu.
2. D. E. Short, professor of
Entomology, Cooperative Extension Service, Institute of Food and Agricultural
Sciences, University of Florida, Gainesville, 32611.
The Institute of Food and Agricultural Sciences is an equal
opportunity/affirmative action employer authorized to provide research,
educational information and other services only to individuals and
institutions that function without regard to race color, sex, age, handicap,
or national origin. For information on obtaining other extension publications,
contact your county Cooperative Extension Service office.
Florida Cooperative Extension Service / Institute of Food and Agricultural
Sciences / University of Florida / Christine Taylor Waddill, Dean
Disclaimer
The use of trade names in this publication is solely for the purpose of
providing specific information. The Great Rocky Mtn. Foliage Co.
Inc./Plantscaping.net/ 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.
Copyright Information
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and Agricultural Sciences (UF/IFAS) for the people of the State of Florida. UF/IFAS
retains all rights under all conventions, but permits free reproduction by all
agents and offices of the Cooperative Extension Service and the people of the
State of Florida. Permission is granted to others to use these materials in
part or in full for educational purposes, provided that full credit is given
to the UF/IFAS, citing the publication, its source, and date of publication.
