Insect enemies of house plants and their control


Material Information

Insect enemies of house plants and their control
Physical Description:
5 p. : 27 cm.
Johnson, G. V
United States -- Bureau of Entomology and Plant Quarantine
U.S. Dept. of Agriculture
Place of Publication:
Publication Date:


Subjects / Keywords:
Insect pests -- Control   ( lcsh )
Insecticides   ( lcsh )
House plants   ( lcsh )
federal government publication   ( marcgt )
non-fiction   ( marcgt )


General Note:
Caption title.
General Note:
At head of title: U.S. Department of Agriculture, Bureau of Entomology and Plant Quarantine.
General Note:
"E-524 ; January 1941."
Statement of Responsibility:
by G.V. Johnson.

Record Information

Source Institution:
University of Florida
Rights Management:
All applicable rights reserved by the source institution and holding location.
Resource Identifier:
aleph - 030270833
oclc - 607535339
System ID:

Full Text

U. S.
E-524 AGRICULThR[ January 1941


By G. V. Johnson, Division of Truck Crop and Carden
Insect Investigations

Plants in houses or window boxes often become infested with various
insects or other pests. Some of these pests may attack the foliage chiefly,
while others may affect only the underground parts. The ones most commonly
found are mealybugs, scale insects, whiteflies, aphids, red spiders, thrips,
fungus gnats, and earthworms. The object of this paper is to give brief
descriptions of these pests, followed by suitable control measures.

Mealybugs can be recognized by their general appearance, which is
that of small objects that have been dusted with meal or flour. They are
soft-bodied insects and move about very little. The eggs are placed in
white cottony or fuzzy sacs, which are usually a little larger than a full-
grown mealybug. The insects and egg sacs are usually found at first on the
underside of the leaves along the midrib or in the crevices where the leaves
join the stem of the plant. Mealybugs obtain their food by sucking the plant
juices, and, when they are abundant, the plant soon has an unthrifty appear-
ance and growth is retarded. Mealybugs attack many plants, but they are
especially troublesome on such plants- as coleus, fuchsia, cactus, fern,
begonia, croton, gardenia, geranium, orchid, poinsettia, citrus, ivy,
ageratum, and dracaena.

A scale insect is characterized by the small shell-like covering or
scale which covers its body. There are many forms, ranging from round or
oval to somewhat rectangular, and one has the shape of an oystershell. In
color these insects range from white to black, but browns and grays pre-
dominate. They are most often found on the stems of plants, but they may
feed on the leaves and fruit as well. Their damage to the plant is similar
to that of mealybugs in that they obtain their food by sucking the plant
juices. Heavy infestations may not only cause retardation in growth, but
also the destruction of the plant. Scale insects attack a wide variety of
plants, among which are palms, rubber plants, citrus, ivy, vinca, croton,
and ferns. ARY

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Whiteflies are among the commonest insects found on ornamentals in
the house, greenhouse, or window box. These small insects get their name
from their appearance; their wings are snowy white, whereas their bodies
may be yellowish or pinkish. When the plants are disturbed, the adults take
flight and are easily recognized while flying over and around the foliage.
The younger forms of the whitefly are wingless and pale green, and they
attach themselves to the under surfaces of the plant. Both the adults and
the young feed, as do the mealybugs and scales, by sucking the plant juices.
Infested plants lack vigor, and, when severely infested, may wilt, turn yel-
low, and die. The plants most commonly affected include geranium, fuchsia,
ageratum, lantana, coleus, begonia, calendula, solanum, and many others.

Aphids, or plant lice, are also common pests of a very wide variety of
ornamental plants. These insects are soft-bodied, usually green, although
some forms, such as the nasturtium aphid, are nearly black, and others are
pink, red, or brown. They usually live in colonies or clusters on the most
tender portions of the plant. Both winged and wingless plant lice may often
be seen in the same cluster. Aphids feed by sucking the plant juices and,
when abundant, cause severe curling and shriveling of the infested leaves and
growing tips. Cne or more species of aphids attack nearly every species
of ornamental plant.

Thrips are of several kinds. They are slender-bodied insects, yellow-
ish to brown or black, the immature forms of which are without wings, whereas
the mature forms have wings and can fly readily. They are difficult to see,
however, because of their small size. The thrips differ from aphids and
scales in their manner of obtaining food in that they first rupture the plant
tissue with their mouth parts and then suck the plant juice. Their feeding
causes a whitish spotting or "silvering" of the foliage, and the edges of
the leaves wither, curl up, and die. Small black specks, which represent
excretion from feeding, are usually present on the leaves of plants on which
these insects have fed. Fuchsia, croton, cineraria, ageratum, and many
other ornamental plants are attacked by thrips.

Red spiders (or mites) are not true insects, since they have 8 legs
and insects have only 6. They obtain their name from the resemblance they
bear to spiders, but are so small as to be scarcely visible to the naked eye.
Red spiders vary in color, but are usually reddish or greenish. They do
most of their feeding on the under surfaces of the leaves by extracting the
plant juices, but in cases of heavy infestation they feed on both surfaces
of the leaves and on the stems of the plant, often covering the area over
which they roam with a light web. Fed-over leaves first have a whitish
appearance, later turning brownish and oftentimes dying. Most plants are
subject to the attack of red spiders, but some of the smooth, hard-leaved
plants, such as certain palms, are only moderately injured.

Funyg.u gnats are small, delicate, flylike insects. The adults are a
nuisance in the house, as they fly to light and may be found, when present,
swarming over the windows. The immature forms are small white maggots, and
they live in the soil in pots of plants. They are particularly fond of soils
containing large quantities of decaying vegetable matter. The maggots cause


injury to the root systems by burrowing in the soil and, whcn abundant, they
may cause actual injury by feeding on the roots and root crowns. Plants in
infested pots appear unhealthy, and root rots often follow the attacks of
these insects.

Earthworms often find their way into soil used in potting plants and
breed very rapidly under favorable conditions. While they do not injure
the plants through direct attack, the worms in the soil may injure the
delicate root system by their continuous tunnelling.

Leaf-eating insects, such as caterpillars and other wormlike forms,
beetles, and grasshoppers, which feed by biting or tearing and swallowing
portions of the foliage and flowers of plants, may at times invade flower
boxes and defoliate the plants. They rarely occur on plants in the home.
As only a few specimens are likely to be found, these may be collected and
destroyed. In case of a heavy infestation, the infested plants should be
treated with a spray made by adding 3 tablespoonfuls of lead arsenate powder
to a gallon of water.

Control Recommendations

Prevention.--The householder must be constantly on guard to see
that plants brought into the house are not infested with insects. It is
much easier to keep an insect from being introduced than to eradicate an
infestation after it has become established. When plants are to be brought
into the house or placed in a window box, a thorough inspection of the plants
and pots should be made to see that they are not infested with any pests.
Whenever repotting is necessary, be sure that insect-free soil and pots are
used. Bouquets that are brought into the house should be examined to see
that they do not harbor any pest which may be readily transferred to other

Treatment.--The control of these pests, once they have become estab-
lished on the plant, is dependent upon a timely, careful, and thorough
application of the proper remedy, In some cases applications at weekly
intervals may be required. Since scales, mealybiigs, aphids, whiteflies, and
red spiders obtain their food by sucking the plant juices, they cannot be
reached with a stomach poison, such as lead arsenate, paris green, or calcium
arsenate. It is necessary to apply a material to the body of the insect so
as to kill by actual contact. There are many such materials on the market,
the most common of which are nicotine sulfate, pyrethrum dusts and extracts,
derris powder and extracts, tobacco dust, white oil emulsions, and thio-
cyanate sprays.

Manufacturers who sell their products interstate are required by law
to label plainly all packages containing insecticides and to show the
quantity of the active ingredients so the buyer can readily satisfy himself
that he is obtaining the proper material. Directions for the use of commer-
cial preparations are usually given on the containers in which they are sold.

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