Front Cover
 Table of Contents
 The insects
 Spider mites
 Miscellaneous pests of minor...
 The insecticides
 Equipment for applying insecti...
 Historic note

Group Title: Bulletin - University of Florida. Agricultural Experiment Station ; 595
Title: Insect pests of ornamental plants
Full Citation
Permanent Link: http://ufdc.ufl.edu/UF00027483/00001
 Material Information
Title: Insect pests of ornamental plants
Series Title: Bulletin - University of Florida. Agricultural Experiment Station ; 595
Physical Description: Book
Creator: Kuitert, L. C.
Publisher: University of Florida Agricultural Experiment Station
Publication Date: 1958
 Record Information
Bibliographic ID: UF00027483
Volume ID: VID00001
Source Institution: University of Florida
Rights Management: All rights reserved by the source institution and holding location.

Table of Contents
    Front Cover
        Page 1
    Table of Contents
        Page 2
        Page 3
    The insects
        Page 4
        Page 5
        Page 6
        Page 7
        Page 8
        Page 9
        Page 10
        Page 11
        Page 12
        Page 13
        Page 14
        Page 15
        Page 16
        Page 17
        Page 18
        Page 19
        Page 20
        Page 21
        Page 22
        Page 23
        Page 24
        Page 25
        Page 26
        Page 27
        Page 28
        Page 29
        Page 30
        Page 31
        Page 32
    Spider mites
        Page 33
        Page 34
    Miscellaneous pests of minor importance
        Page 35
        Page 36
        Page 37
    The insecticides
        Page 38
        Page 39
        Page 40
        Page 41
        Page 42
        Page 43
        Page 44
    Equipment for applying insecticides
        Page 45
        Page 46
        Page 47
        Page 48
        Page 49
        Page 50
        Page 51
    Historic note
        Page 52
Full Text

Bulletin 595

J. R. BECKENBACH, Director




Fig. 1.-Florida red scale on upper (left) and lower surfaces of Ligustrum
japonicum leaves. The males are concentrated on the upper side.

Single copies free to Florida residents upon request to

April 1958


S 4
.....-....-- 5

THE INSECTS ...............
Scale Insects ............
Armored Scales -.
Soft Scales ....
Mealybugs ............
Aphids or Plant Lice
W hiteflies .............-

...-.-.--.-.-.- ....- ...... 7
.-...- ...-- -... ..... 10
....- 12

Treehoppers ....-...- ....... .......-... --..-. 14
T h rips ...... .- --....... .. .............. -. ...- .. .. 15
Lacebugs ............... ...... ....--...... .... ----. ------ -----17
Lepidopterous Larvae or Caterpillars .......................... -- .. .. 18
Leaf-eating Caterpillars ........ -..-.... ......... ...... -- ..... 20
Underground Caterpillars .........---......-.. ...... ..... ------ .... 23
Nettling Caterpillars .................... ....-- ----....- ..--...... 23
Beetles and. Grubs .......-...........-... .........- --- ......- --- 24
June beetles ................. .-----.. .... ..- .. 25
Leaf beetles .....-.................. ..--- ..........-------------- 25
Grasshoppers, Katydids and Crickets .............-....-....-- ----- --.. 26
Leaf M iners ............--...... ......--- ..-- ..... ---- ---- -- 28
B orers ............. ---......--- ..... .......... .......... 31
SPIDER MITES ...........-----.....-------......--.-- ---- ..... 33
MISCELLANEOUS PESTS OF MINOR IMPORTANCE ..........-..-...........-.- ..-...-..- 35
Earw igs ........... ........ -.---------- .... ..... .. 35

Leafcutting Bees ...........-......
Snails and Slugs ................. ............
M illipedes .............. .. ........
Centipedes ..........--.....
Sowbugs ...........-- --.
THE INSECTICIDES .............. .
Oil Emulsions ................... ----------
Chlorinated Hydrocarbons ..............
Organic Phosphates ................-------
System ics ................ ............
ACKNOWLEDGMENTS ...... -------......
REFERENCES ............--... .....

... ....... .............. 36
....... ...... ..... -....- ..-- 37
................... .. ..... .... 3 7
........ ... -.. -. -.... ..- ...-... 38
............... ........... ...- ...-- ..-..... ....... 38
-.......... ..... -..--.. ........ ....... 38
...... ...... .. ... .. ......- ..- .... 4 1
.. ... .... .. ........ ... ....... 41
~...- ~~-......... ........ ..... 45
.. ..............-.... 50
........................... 51



L. C. KUITERT, Entomologist

The increased interest in the growing of ornamental plants
has created a demand for information on the control of the
insects and other pests which attack them. This publication is
intended primarily as an aid for home gardeners, although it can
be used as a guide by custom spray operators and nurserymen.
The information is intended to serve as an over-all guide for
the control of the more important pests.
Ornamental plants are subject to attack by a variety of
insects and related pests. Some insect outbreaks occur at definite
seasons of the year (lacebugs and leaf beetles), while others
are active throughout the year (scale insects and borers).
Numerous variations occur in the methods of locomotion, manner
of feeding, life histories and reproductive habits of the pests.
For these and other reasons the insects are discussed under
several categories to aid the gardener in the control program.
For example, insects feeding between the epidermal layers of
the leaf (leaf miners) require control methods different from
those living on the leaf surface, and those insects which lose
the ability to move about during portions of their life cycles
(scales) require more thorough applications of insecticides than
many of those which move about freely.
It is important to learn to recognize the specific pests to aid
in deciding on the best measures for their control. This is
especially desirable since many newer insecticides are specific
in action. A material may be very effective in controlling one
pest and be of little value against closely related species.
The suggestions given for control are based principally on
results of experiments in the Gainesville area, though some of
the work was done in cooperation with nurserymen in other
parts of the state. Numerous observations on the control ob-
tained were made in nurseries where these recommendations
were followed. Some of these suggestions may have to be modi-
fied in certain places, especially in subtropical areas. It is antici-
pated that these suggestions will be supplemented in the future
to provide a well rounded state-wide pest control program.

Florida Agricultural Experiment Stations


Scale insects are serious pests of many ornamental plants.
The scales are so different from the usual concept of insects that
they are often mistaken for fungus growths. They have suck-
ing mouth parts and feed on plant juices. Scales generally are
quite small and occasionally they become so numerous that they
literally coat the leaves and stems. Heavily infested plants
appear unhealthy and produce very little new growth. The
foliage develops chlorotic areas and may drop prematurely and
portions of twigs and branches may be killed. Scale insects are
widely disseminated through the movement of infested nursery
stock, although in some instances they may be carried from
infested plants by birds and other animals. They are divided
into three groups for convenience: (1) armored scales, (2) soft
scales and (3) mealybugs.

Fig. 2.-Florida red scale on podocarpus (5X). The armor is removed from
some scales. Left pointers show the armors, right the insects.

Insect Pests of Ornamental Plants

Armored Scales.-These insects secrete a waxy, hardened,
protective covering which is not an integral part of the insect's
body (Fig. 2). This protective covering, under which the insect
lives and feeds, is called the scale or armor, hence the common
name. The tiny scale may be circular, semi-circular, oblong or
pear-shaped. Adult females vary from about 1/12 to 1/8 inch
in diameter or length. The adult males are tiny, two-winged,
gnat-like insects, and are seldom observed. The sexes cannot
be distinguished in the young larvae but are easily differentiated
in the older immatures. As a general rule the late immature
stage of the male is similar to the female but much smaller.
There are a few exceptions, as in the tea scale, fern scale and
citrus snow scale, where the males, because of their white color,
are more conspicuous than the females.

Fig. 3.-Tea scale on camellia. This scale is one of the most difficult
to control.
Although many kinds of armored scales attack ornamentals,
they are very much alike in habits and life history. A single
species, Florida red scale (Figs. 1 and 2), will suffice to illustrate
them. The female deposits the eggs under the scale covering.
A single female may deposit more than 300 eggs, and these
hatch in one to two weeks or longer, depending on the tempera-

Florida Agricultural Experiment Stations

ture. The young scale, known as a crawler, is broadly oval in
shape, flattened and bright yellow in color. It has the ability
to crawl and move about freely. The crawler moves out over
the plant to the succulent new growth, selects a place to settle,
inserts its mouthparts into the plant tissue and, in the case of
the female, remains there for the rest of its life. The adult
stage is reached in five to 11 weeks. There are several over-
lapping generations a year.
Some species infest only the foliage; others are found only
on the branches, while others may attack both foliage and
branches. Many woody ornamental
plants, including camellia, azalea,
gardenia, holly, hibiscus, citrus,
rose, ixora, crape-myrtle and ole-
ander, as well as a variety of
succulent ornamental plants, are
attacked by one or more species of
armored scale. The more import-
ant species are the Florida red
scale, tea scale (Fig. 3), oyster
shell scale (Fig. 4), white peach
scale, lesser snow scale, purple
scale, cyanophyllum scale and
dictyospermum scale.
Soft Scales.-Whenever large
numbers of ants are observed on a
Fig. 4.-Camellia scale on plant one should suspect the pres-
camellia. It is also referred ence of soft scales, mealybugs,
toas foster shell scale. (About aphids or whiteflies. These insects,
in addition to sucking plant juices,
excrete a sweet liquid called honeydew which covers the foliage
and is attractive to ants. This sticky material is unsightly and
makes an excellent medium for the development of a black fungus
called sooty mold. This fungus retards the growth of the plants
to some extent by reducing light, thus interfering with photo-
synthesis. Sooty mold usually weathers away following control
of the insect infestation.
In the soft scales, unlike the armored scales, the waxy secre-
tion is an integral part of the insect's body. Some of these
scales are covered with a waxy, cottony material while others
are naked. The soft scales vary considerably in size and shape.
Some are flat or slightly convex and others are almost spherical.

Insect Pests of Ornamental Plants

Soft scales are larger than the armored scales and vary from
1/12 to 1/3 inch in length. Usually the eggs are laid under-
neath the female and hatch in one to three weeks. In some
species a single female lays several thousand eggs. The young
scales, or crawlers, move about over the plants for several weeks
before settling down. Development is slow, and periods of sev-
eral months to almost a year may elapse before the female be-
comes an adult. Important species are the hemisperical scale,
tessellated scale, pyriform scale (Fig. 5), black scale, magnolia
soft scale, Florida wax scale (Fig. 6) and liriodendron scale.
These scales attack most citrus varieties and many woody orna-
mental plants, including allamanda, azalea, chinaberry, croton,
gardenia, hibiscus, holly, oleander, magnolia, ixora, palm and
rose. Other ornamental plants which scales infest include
African violet, asparagus fern, cactus, coleus, chrysanthemum,
fern, foliage plants, ivy, orchid and verbena.

Fig. 5.-Pyriform scale-a soft scale-on kalopanax. (Slightly enlarged.)

Mealybugs.-Mealybugs are important pests of annuals and
perennials, in addition to some of the woody ornamentals. Like
the soft scales, they excrete honeydew in large amounts and
this attracts ants and serves as a medium for the development

Florida Agricultural Experiment Stations

of sooty mold. Mealybugs are soft-bodied scale insects which
are usually covered with a powdery or cottony, wax-like material.
They vary from 1/5 to 1/3 inch in length when mature. With
a few exceptions, mealybugs are able to move about throughout
their lives.

Fig. 6.-Florida wax scale-immature and adult. (Twice natural size.)

The females lay their eggs in white cottony sacs. Some 200
to 400 yellowish or orange eggs are laid in the sac. The eggs
hatch in about two weeks and from six to eight weeks are re-
quired for the crawlers to become adults. The reproductive
cycle is not interrupted during mild winters in Florida, although
it may be retarded. Important species are the citrus mealybug,
long-tailed mealybug (Fig. 7) and cottony cushion scale (Fig. 8).
Some of the most common host plants are azalea, cactus, citrus,
coleus, croton, foliage plants, holly, pecan, pittosporum and rose.
Control of Scale Insects.-Control of some of the scale insects
is often difficult, due largely to the failure to obtain thorough
spray coverage. To be effective, the spray must come into con-
tact with the insects. Care should be taken to insure that the
spray is applied to all parts of the wood, twigs and leaves, as
the crawlers move about over the plant and are found in the

Insect Pests of Ornamental Plants

crevices of bark, axils of leaves and under debris. Furthermore,
many of the scales are shielded by the waxy protective covering.
Sprays must be applied so that each insect is wet sufficiently
to allow the spray to penetrate through the protective covering.
Since the recommended insecticides are most effective against
scale insects in the crawler and immature stages, the insecti-
cide should be applied when most of the scales are in these
stages. For many species of scales this period is correlated
closely with the time the new growth develops on the plants.

Fig. 7.-Long-tailed mealybugs on coonti. (Twice natural size.)
Materials effective in controlling scale insects are oil emul-
sions (mayonnaise type), 25 percent wettable powder malathion
and 15 percent wettable powder parathion. Use oil emulsion
at the rate of 1 quart in 20 gallons of water (3 tablespoonfuls
per gallon); malathion at the rate of 1 pound in 20 gallons (4
level tablespoonfuls per gallon) and parathion at the rate of 1
pound in 50 gallons (4 level tablespoonfuls per 3 gallons).
Never apply oil emulsion when temperatures are apt to ex-
ceed 850 to 90 or drop below 420 F. Do not apply oil sprays
to new growth until it has "hardened off," or to tender succulent
plants. Never apply oil emulsion at less than eight-week inter-
vals. Malathion and parathion can be applied during any season
and at frequent intervals without danger of plant injury. How-
ever, they are phytotoxic to several plants, including hibiscus
and Podocarpus nagi.

Florida Agricultural Experiment Stations

Fig. 8.-Cottony cushion scale (a mealybug) on pittosporum.
(About natural size.)
Aphids, or plant lice, infest nearly all types of plants. They
live in colonies and commonly are found on annuals, perennials
and the tender growth of woody ornamentals (Fig. 9). They
have sucking mouth parts and feed on plant juices. As a result
of the continuous draining of these juices, the tender growth
becomes stunted. Sometimes the leaves curl and become dis-


Insect Pests of Ornamental Plants

torted. Aphids may also harden
ment of the flowers.

the buds and cause disfigure-


Fig. 9.-Rose buds infested with aphids. (Slightly enlarged.)

Aphids are soft-bodied and may be whitish, greenish, yellow-
ish, pink, brown or black. They are usually less than 1/ inch
in length and most aphids are wingless. The rate of develop-
ment and reproduction is extremely rapid and many generations
may be produced in a year. Unlike most insects, aphids seldom
lay eggs but give birth to living young. Another peculiarity of
aphid reproduction is that in most generations all individuals
are females which reproduce parthenogenetically; that is, with-
out mating. A single female often produces 100 progeny during
her lifetime and these young aphids mature six to seven days
after birth. When colonies become overcrowded or the plants
harden, winged forms may appear, which fly to other host plants
and establish new colonies.
Aphids frequently excrete honeydew in such quantities as to
moisten the soil underneath the infested plant. This is especially
common during the spring under oaks, crape-myrtle and pecans.
Honeydew attracts ants in large numbers and makes an excel-
lent medium for the development of sooty mold.


Florida Agricultural Experiment Stations

The aphids most often found on ornamental plants are the
potato aphid, green citrus aphid, black citrus aphid, green peach
aphid, melon aphid, oleander aphid and crape-myrtle aphid.
Plants frequently found infested are camellia, citrus, crape-
myrtle, gardenia, hibiscus, ixora, oleander, palm, rose and nearly
all annuals and herbaceous perennials.
Control.-Aphids are easily killed with insecticides, though
applications may have to be repeated as reinfestation easily oc-
curs from adjacent areas. Malathion 25 percent wettable powder
and nicotine sulfate (Black Leaf 40) sprays are effective in con-
trolling aphids. Use malathion at the rate of 1 pound in 25
gallons or 1 ounce (4 level tablespoonfuls) in 11/2 gallons of
water. Nicotine sulfate is used at the rate of 1 pint in 100 gal-
lons or 1 teaspoonful per gallon of water. A liberal amount of
soap or other spreader and sticker should be added to nicotine
sprays. Parathion and demeton are effective aphicides, but
must be used with extreme care. Lindane is effective in con-
trolling some species of aphids. Follow the instructions on the
label for diluting with water.

Whiteflies restrict their feeding to foliage, and nearly always
are found on the lower surface. Both adult and immature stages
suck plant juices. Heavy feeding sometimes gives the infested
leaves an unhealthy appearance and may cause the leaves to
turn yellow and die. Whiteflies also excrete honeydew which
provides an excellent medium for the development of sooty mold.
Adult whiteflies are tiny creatures about 1/16 inch in length.
They have four wings which, with the top of the body, are covered
with a white powdery wax, giving the insects their common
name. They resemble tiny white moths. The immature stage
(Fig. 10) looks somewhat like small scale insects, and they re-
main attached to the leaf until mature. They are about the size
of a small pin-head, oval, flattened and light green in color.
The tiny pale yellow eggs are laid singly on the underside
of the leaves and are attached by a tiny stalk. A single female
lays about 150 eggs. The eggs hatch in one to three weeks.
After hatching the young nymph (crawler) moves about for
several hours and settles on the underside of the leaf. It inserts
its mouth parts, feeds for several days and then molts (sheds
its skin) and in the process increases in size. Three such molts
occur before the insect enters the pupal or resting stage where

Insect Pests of Ornamental Plants

it transforms to the adult. The entire life cycle from egg to
adult requires from about six weeks to almost a year. Consider-
able variation has been noted in the length of the life cycle,
even among eggs laid in the same leaf on the same day.

Fig. 10.-Immature whiteflies on hibiscus. (Slightly enlarged.)

The citrus whitefly is the species most commonly found on
ornamentals, and it has three generations a year in Florida. The
spring brood of adults is at its maximum in late March, the
summer brood in June and the fall (and largest) brood in late
August and early September. Chinaberry is one of the favorite
host plants and it acts as a source or reservoir from which other
ornamental plants become infested. Other host plants frequently
infested are the gardenia or cape jasmine and citrus varieties.
Gardenia rarely is observed without a whitefly infestation. Other
host plants attacked are hibiscus, crape-myrtle, ligustrum, alla-
manda and many annuals.
Control.-In the past considerable effort was required to
eliminate whitefly infestations. With the advent of the phos-
phatic insecticides this problem has been minimized. Time the
applications to coincide with the appearance of each brood.

Florida Agricultural Experiment Stations

Delay the insecticide application until most of the adults have
disappeared, thus allowing most of the eggs to hatch. When
applying insecticides pay particular attention to treating the
lower sides of the leaves. Frequently it is necessary to repeat
the application because whiteflies may easily reinfest treated
Malathion 25 percent wettable powder at the rate of 1 pound
in 20 gallons of water or % ounce (3 level tablespoonfuls) per
gallon is effective. Parathion 15 percent wettable powder at
the rate of 1 pound in 100 gallons or 1/2 ounce (2 level tablespoon-
fuls) in 3 gallons is effective, but may injure some varieties of
hibiscus. Emulsifiable concentrates of these materials can be
substituted for the wettable powder formulations. Follow direc-
tions on the con-
tainer for mixing
with water. Ap-
plications of oil
emulsion or deme-
ton (Systox) are

Although tree-
hoppers are rath-
er common in-
sects, they are
not considered
important as a
group. One spe-
cies, the thorn-
bug, Umbonia
crassicornis A &
S, is an exception
to this general
rule in Florida.
Most species live
on trees or low
bushes and when
disturbed hop
quickly to an-
Fig. 11.-Treehopper or thornbug, Umbonia other part of the
crassicornis A. & S., infesting pithecolobium twig.
(11/2 times natural size.) plant.

Insect Pests of Ornamental Plants

The thornbug is aptly named for, as it clings to the stem of
a plant, the bug closely resembles a thorn. The adult is about
1/ inch in length. It is greenish with brown markings and has
a large projection arising from the front part of the body (Fig.
11). The thornbug is a sucking insect and feeds on plant juices.
In addition to the injury caused by feeding, these insects
secrete honeydew which makes possible the development of sooty
mold. Infestations are usually attended by ants seeking the
honeydew. Sometimes automobiles parked under heavily in-
fested trees are covered with these excretions. Also the females
cut slits in the stem and insert their eggs into the stem. Fre-
quently the terminal twigs and smaller branches are found
covered with the nymphs and adults. Heavy infestations have
caused serious injury to many trees in central and southern
Plants attacked are principally in the legume family and in-
clude pithecollobium, royal poinciana, acacia, Calliandra (powder
puff tree), woman's tongue tree (Albizia lebbeck), mimosa, cas-
sia and tamarind.
Control.-Control of thornbugs has proven difficult. The
chlorinated hydrocarbon insecticides (DDT, chlordane, etc.) have
generally reduced the infestation but failed to give satisfactory
control. Nicotine sulfate and parathion have given best control.
Use 1 teaspoonful of nicotine sulfate or 11/2 level tablespoons of
15 percent wettable powder parathion per gallon of water.

Thrips are serious pests of ornamental plants. For several
weeks during the spring there are few flowers which are not
infested with them. They restrict their feeding to the foliage,
buds and flowers. Injury is caused by puncturing the plant
tissue and then sucking the exuding sap. Infested leaves have
a stippled appearance similar to that resulting from mite infesta-
tions. Usually it is not difficult to distinguish between mite and
thrips infestations as thrips leave small brownish specks of
excrement (Fig. 12) wherever they feed. Frequently infested
buds fail to open or the flowers are deformed. Feeding punctures
on the flowers turn brown and the petals eventually become
streaked and discolored. They are very active and when alarmed
will turn up the tip of the abdomen as if to sting. Flowers
suspected of being infested should be shaken over a sheet of
white paper to detect the thrips.

Florida Agricultural Experiment Stations

Adult thrips are small and vary in size from less than 1/25
to 1/8 inch in length. They are slender insects and usually
brownish or yellowish in color. The tiny eggs are laid on and
in the plant tissues. Each female lays from 25 to 50 eggs, which
hatch in several days to three weeks. Two to four weeks later
the adult thrips appear. A peculiarity of thrips reproduction
is that in some species males may be absent completely or, even
when present, reproduction may take place parthenogenetically
-that is, without mating. Normally, there are three to five
generations a year. However, some species have but one gen-

Fig. 12.-Varnish-like specks of thrips excrement on lower sides
of azalea leaves.

The most important species on ornamentals are the Florida
flower thrips, red-banded thrips, Cuban-laurel or ficus thrips and
the greenhouse thrips. The flower thrips confines its feeding
to flowers and buds of practically all types of plants. The green-
house thrips feeds on foliage and is a common pest on avocado,
azalea, citrus, croton, euonymous, rose and viburnum. The
Cuban-laurel thrips causes leaves to become curled and distorted.

Insect Pests of Ornamental Plants

Control.-Thrips which feed on foliage are readily controlled
with 4 to 5 percent malathion, 5 percent DDT or 1 to 11/2
percent lindane dusts. Spray applications of 1 pound 25 percent
wettable powder malathion in 25 gallons of water (1 ounce in
11/ gallons) or 1 pound 50 percent wettable powder DDT in 50
gallons (1 ounce in 3 gallons) are excellent remedies. Fifteen
percent wettable powder parathion at the rate of 1 pound in 100
gallons (1 ounce in 6 gallons) is also effective.
At present there is no completely satisfactory control for
flower thrips. Insecticides, when used at an effective concentra-
tion, cause some spotting and discoloration of the petals. Also,
flower thrips breed in the flowering parts of weeds, grasses and
trees, and there is a constant migration from these plants to
the ornamentals. This eliminates the usual advantages gained
by applying insecticides possessing a residual action. Malathion,
DDT, lindane and parathion used as sprays at one-half the above
concentrations and applied without runoff at two to four-day
intervals are the most satisfactory methods for controlling flower
Lacebugs injure plants by sucking the plant juices. They
are commonly found on the lower sides of infested leaves. Both
adults and nymphs puncture the plant tissues and withdraw the
chlorophyll, causing the leaf to have first a stippled, unhealthy
appearance and, as feeding continues, a grayish and finally a
brownish sunburnt appearance. Usually the whitish cast skins
and blackish-brown, varnish-like specks of excrement are found
on the infested leaf.
Lacebugs are small delicate insects (Fig. 13). The adults
are easily recognized by the lace-like or gauze-like appearance
of the wings and other expansions of the body. The adults are
about 1/8 inch in length and the wings rest flat on the back. The
young are often dark, spiny insects quite different in appearance
from the adult. Most lacebugs lay their eggs on the lower leaf
surface, although some are inserted in the leaf tissues. These
hatch in two to four weeks. Two to three weeks more are re-
quired for the nymphs to reach adult stage.
These common pests include several that were given the
names of the plants they infest and include the azalea, hawthorn,
oak and sycamore lacebugs. The hawthorn lacebug also attacks

Florida Agricultural Experiment Stations

Fig. 13.-Lacebugs on sycamore leaf. They also deposit excrement on the
leaf. (Inset enlarged about 5 times, others slightly enlarged.)

Control.-Several of the new insecticides are effective in con-
trolling lacebugs. More than one application is required fre-
quently to clean up an infestation, since the materials are not
effective against the eggs. Nymphs hatching from eggs subse-
quent to treatment may not be killed. Treated plants also are
often reinfested from nearby untreated plants. Malathion and
DDT sprays or dusts control lacebugs when applied as recom-
mended for the control of thrips. Infestations are cleaned up
also with oil emulsion sprays.

Caterpillars are the immature stage of moths and butterflies.
They are often referred to as "worms". All caterpillars have
chewing mouthparts and although only a few species are de-
structive, they are among the garden's worst pests. The body
is usually cylindrical in shape and either slender or robust.
However, some are short and oval, while others are flattened.
Caterpillars have three pairs of jointed, true legs on the front
of the body and usually four pairs of unjointed, soft, fleshy
projections called "prolegs" on the abdomen, with a fifth pair

Insect Pests of Ornamental Plants

at the end. The prolegs have
can hold onto a leaf or twig.

tiny hooks so that the caterpillar

Fig. 14.-Egg mass of azalea defoliator. Most of the eggs have hatched.

The life cycle of moths and butterflies is divided into four
distinct stages: the egg, the destructive caterpillar or larva, the
pupa or resting stage and the adult. Although there is consider-
able variation within the group, the life history is quite similar
for the different species. In general, adult females usually lay
their eggs on the host plant (Fig. 14). Each female lays several
hundred eggs, singly or in clusters. The eggs hatch in two days
to two weeks during summer but require considerably more
time in winter. The larvae begin feeding immediately after
hatching (Fig. 15). After feeding for several days, the cater-
pillar molts (sheds its skin) and in the process increases greatly
in size. The period between each molt is referred to as a larval
instar. Caterpillars pass through five to seven larval instars
before they enter the pupal stage. Many moth larvae construct
small earthen cells below the surface of the soil in which they
change to the pupa or resting stage, while others construct
silken cocoons. Two to three weeks are spent in the pupal stage,
where they transform into adult moths. After the adult emerges
from the soil or cocoon, mating takes place and the female is
ready to lay eggs. Under optimum conditions three to six weeks
are required for most moths to develop from egg to adult.

Florida Agricultural Experiment Stations

Fig. 15.-Left and right leaves show injury of early instars of
azalea defoliator.

In general, the life history of the butterflies is similar to
that of the moths except for the pupal or resting stage. Most
butterfly caterpillars attach themselves by a button or girdle
of silk to a twig or other projecting object and change into a
chrysalis within which the transformation into the butterfly
occurs. An exception to this rule is the canna leaf roller, which
pupates within the folds of the leaf.
The large number of variations found within this group pre-
cludes a discussion of the various representatives. Because of
their habits and control, they are grouped into three categories:
(1) Leaf-eating caterpillars, (2) underground caterpillars and
(3) nettling caterpillars, i.e., having poisonous hairs. Another
group which has assumed the habit of mining between the two
leaf surfaces is discussed in the section on Leaf Miners.

There is considerable variation within this group, which in-
cludes the oleander caterpillar, bougainvillea caterpillar, canna
leaf-roller, bagworm, measuring worms, armyworms, hornworms
and tent caterpillars. Some of the larvae, such as the azalea

Insect Pests of Ornamental Plants

Fig. 16.-Mature larva of azalea defoliator. (About natural size.)

defoliator (Fig. 16), restrict their feeding to the foliage of a
single host plant. Other larvae, as the bagworm (Fig. 17) and the
okra caterpillar (Fig. 18),
restrict their feeding to '
closely related plants. Still
others, as the corn earworm
or measuring worm, attack
almost any type of vege-
tation. In general these
"worms" vary in size from
about 1/ inch in length to
large hornworms (Fig. 19)
which may be more than 4
inches long. A few species,
as the azalea defoliator and
the tent caterpillars, are
gregarious and many larvae
are found on a single
branch. Fig. 17.-Bagworms-the bag is en-
Control. e c i l- argued as the larva develops. (About
Control.-The caterpil- natural size.)

Florida Agricultural Experiment Stations

Fig. 18.-Okra caterpillar, also a pest on hibiscus. Inset: Larva about
11/2 times natural size, and immature whiteflies also are present.

lars which feed in clusters are readily eliminated by pruning
out the infested twigs and destroying the larvae. DDT applied
as a 5 or 10 percent dust or as a spray containing 1 pound of 50
percent wettable powder in 50 gallons (1 ounce in 3 gallons)
is effective in controlling many caterpillars. Another good con-
trol remedy is malathion applied as a 4 or 5 percent dust or
as a spray containing 2 pounds of 25 percent wettable powder

Fig. 19.-Larva of Achemon sphinx moth. Its hosts are grapes and
Virginia creeper.

Insect Pests of Ornamental Plants

in 50 gallons (1 ounce in 11/2 gallons). Applications of dieldrin
or parathion dusts or sprays are beneficial if applied when the
caterpillars are young.

Members of this group have similar habits and are called
cutworms. For the most part they are noctural and remain
hidden in the ground near the host plant during the day. They
work at about ground level, cutting off the seedling plant so
that it falls over and dies. Many succulent plants are subject
to attack. In general, cutworms are smooth, shiny caterpillars,
gray or brownish in color with black markings.
Control.-Poison baits containing chlordane, aldrin or DDT,
which are available in prepared form, sprinkled about the base
of the plant are the best materials to use. Five percent DDT
or 5 percent chlordane dusts and sprays consisting of 1 pound
50 percent wettable DDT in 50 gallons (1 ounce in 3 gallons)
or 1 pound 40 percent wettable chlordane in 40 gallons (1 ounce
in 21/$ gallons) also are effective.

The injury these caterpillars cause to plants is relatively
unimportant. They are discussed because they have poisonous
hairs and should be avoided or
handled with extreme care.
Some of these larvae are curious
slug-like animals often referred
to as slug caterpillars, since they
do not have legs but crawl about
on their flattened bellies like the
slugs. The puss moth cater-
pillar (Fig. 20) is a nondescript
creature with long brownish Fig. 20.-Top view of puss moth
creature with long brownish caterpillar.
hairs which meet in a roof-like
ridge on the back. Interspersed among these long hairs are
short, stiff, stinging spines. When these spines enter the skin,
they cause severe irritation. The puss moth caterpillar feeds
on oak, sycamore and hackberry.
Another slug caterpillar having stinging hairs is the distinc-
tive saddle back caterpillar. The larva is brownish in color and
has a green patch on the middle of the back which may be

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thought of as the saddle blanket. In the middle of the green
patch is a much smaller brown patch, sometimes outlined in white,
which is the sad-
dle. Several rows
of stinging spines
are located along
the sides and
a ends of the larva.
The caterpillar
feeds on a variety
of woody orna-
mentals. The
larva of the Io
moth (Fig. 21)
also has poison-
ous hairs. It feeds
on a variety of
Fig. 21.-Larvae of the Io moth. The spines are Con
sharp and many are connected with poison glands. Control.-Elim-
inate the larvae
by picking off and destroying the infested leaf or twig. Applica-
tion of sprays as suggested for leaf-feeding caterpillars are
Frequently beetles cause injury in the nursery and home
garden. Both adult and immature or larval stages are injurious
and both have chewing mouthparts. The adult beetles have a
hard shell and vary from 1/10 to more than 2 inches in length.
The immature stage of most beetles is known as a grub.
Usually adults feed on foliage, flowers and fruits, while the
larvae or grubs feed on foliage or roots or bore through stems.
There are exceptions to this general rule, as in the blister beetles
where the larvae feed extensively on grasshopper eggs. Many
beetles are beneficial and all gardeners should learn to recognize
these beneficial forms. Both the immature and adult stages of
ladybeetles are predaceous on a variety of pests.
The beetles can be separated conveniently into several groups,
the more important being the June beetles or white grubs and
the leaf-feeding beetles. The larvae and adults of some beetles
have assumed the habit of boring through stems and branches
while the larvae of others have become leaf miners. These
groups are discussed under "borer" and "leaf miners."

Insect Pests of Ornamental Plants

June beetles are the familiar reddish-brown insects which
bang into screens when attracted by lights during the summer.
They are also known as May beetles and June bugs. The adult
beetles feed on foliage and flowers, while the grubs feed on the
roots of grasses. Generally the grubs are serious pests only
in grassy areas, or in soil which has been in sod for several
years and is being planted to another crop for the first time.
White grubs are usually a dirty white color and have a brown
head. They usually take a C-shaped position with the end of
the body curved forward toward the head.
Female beetles lay their eggs in small balls of earth in the
soil in grassy areas. The eggs hatch in about a month. The
young grubs feed on grass roots for several months, shed their
skins (molt) and increase greatly in size. This process continues
until the grub has undergone five or more such molts. The full-
grown grub then forms a cell in the soil where it transforms
to the pupa or resting stage. Several months later the adult
beetle emerges from the soil. Most beetles emerge during June
and July. About two years are required to complete the cycle.

The leaf beetles are so called because they feed upon the
leaves of plants both as larvae and as adults. Most of these
beetles are very small, usually not more than 1/5 inch in length.
Many are a dark metallic color; however, some are tan and others
brown. The larvae of some species feed on plant roots, while
others feed on the leaves. Some species restrict their feeding
to a single plant while others are general feeders and attack
most plants in the flower garden. Usually they gnaw tiny holes
through the leaves or along the leaf margin. Sometimes these
beetles do not chew completely through the leaf, but only eat
tiny holes through the upper epidermis, giving the leaf a pocked
Camellias and azaleas are frequently attacked by several
species of flea beetles. The adults hide in the debris and mulch
on the ground and come out at night and scallop the leaves in
a characteristic pattern. These beetles are about 1/4 inch in
length. The one feeding on camellias is a shiny black, while
that feeding on azaleas is a light-brownish color.
Control.-DDT is the best insecticide to use for controlling
the immature and adult stages of most beetles. Apply 2 pounds

Florida Agricultural Experiment Stations

of 50 percent wettable DDT in 100 gallons of water (1 ounce
in 3 gallons) to the infested plants. Spray applications consist-
ing of 1 pound of 15 percent wettable powder parathion in 50
gallons (1 ounce in 3 gallons) also are effective.

Grasshoppers, katydids and crickets frequently become a
problem in iris beds or the flower garden generally. These in-
sects have chewing mouthparts and eat the foliage, flowers and
sometimes other tender growth. Attacks may occur almost any
time during the growing season.
The true or short-horned grasshoppers are commonly pests
in grassy areas. However, they migrate into gardens and nur-
series when their normal food supply is reduced by adverse
conditions. They vary from about 1 inch to almost 21/ inches
in length. Most grasshoppers are good fliers, and the hind legs
are adapted for jumping.
The lubberly locust is the most troublesome grasshopper in
gardens and nurseries in most sections of Florida. This is the
largest grasshopper in the state. The males are usually 2 inches
long, while the females frequently exceed 21/2 inches. They have
very short wings and are incapable of flight. This grasshopper
is very slow and clumsy in movement, crawling feebly over the
ground after being knocked off of a plant. Due to the weak
hind legs and heavy body, it can leap only short distances. There
are two color-forms of the adults. Some are a striking yellow
color with reddish, brown and black markings and others are
almost black. The young are black with reddish markings. In
the early nymphal stages they are gregarious and 50 to 75
nymphs often are found on a single amaryllis plant.
Several of the tree crickets and false katydids may eat holes
in the leaves of hibiscus, turk's cap, gardenia and other plants.
Damage is rarely severe although the numerous holes in the
foliage are unsightly. These insects are commonly referred to
as long-horned grasshoppers. They are nocturnal and are dif-
ficult to locate during the day. The presence of these insects,
though usually unseen, is made very evident in summer and fall
by the songs of the males.
Tree crickets are delicate insects and many are light green
in color. The snowy tree cricket is commonly found on hibiscus
and turk's cap. This insect is attracted to light and in the
evening is found frequently on window screens or doors.

Insect Pests of Ornamental Plants

One of the false katydids has a curious and yet remarkable
way in which it deposits its eggs on leaves and twigs (Fig. 22).
This frequently attracts attention.

Fig. 22.-Katydid eggs along margin of rose leaf.

Mole crickets, although not serious pests of woody orna-
mental plants, are common pests in nurseries and gardens. They
are about 11/2 inches long, 3/8 inch wide and brownish in color.
The body is covered with short, fine hairs giving the appearance
of velvet. They are well adapted for burrowing in soil. Strong,
shovel-like front legs serve to dig the tunnel. The fore wings over-
lap and are shorter than the abdomen. There are several instars
in the immature stage. The various instars are similar to the
adult in appearance, but are smaller and do not have wings.
Moist, loose soil as found in nurseries and ornamental gardens
is the favorite habitat of mole crickets. They feed largely on

Florida Agricultural Experiment Stations

decomposing organic matter and injury to plants is due to their
burrowing activities. In the process of making burrows, they
loosen the soil and disturb and cut off roots. At times they are
responsible for killing small plants.
Control.-Bait formulations containing chlordane or aldrin,
which are available in prepared form, will eliminate mole cricket
infestations. Five percent chlordane or 21/% percent aldrin dust,
or sprays containing 1 pound 40 percent wettable powder chlor-
dane in 40 gallons (1 ounce in 21/2 gallons) or 1 pound 25 percent
wettable powder aldrin in 50 gallons (1 ounce in 3 gallons), also
are effective.

Fig. 23.-Magnolia leaves damaged by a beetle leaf miner,
Prionomerus calcealus (Say).

All of the groups discussed above are composed of related
forms. The leaf miners are unrelated forms which are grouped

Insect Pests of Ornamental Plants

together because of the mining habit of the immature stages.
All leaf miners are immature insects. In the immature stage
leaf miners are very similar in structure and extremely difficult
to separate, although the adults are quite different and rather
easily identified. The leaf mining habit has developed in all
orders having larval and pupal stages.

Fig. 24.-Injury to nasturtium caused by the serpentine leaf miner maggot.

Leaf miners are among the smallest of the plant-eating
animals. The larvae tunnel through a leaf, feeding on the
parenchymal cells between the upper and lower epidermal leaf
surfaces. This feeding causes a blotch mine or blister when
the larva excavates a broad patch (Fig. 23, magnolia leaf miner);
a linear mine if the larva tunnels straight ahead and a serpen-
tine mine if it follows a winding course (Fig. 24, serpentine leaf
miner). Although leaf miners never live as exposed feeders,
some do emerge from the mine. Caterpillars of the azalea leaf
miner leave the mine when about half grown and make shelters
for themselves. The shelter is made by spinning silk in such a
way that the leaf bends or curls over the larva. The larva is
then known as a leaf-tier but continues to mine from the shelter.
Another exception is the palm leaf miner, also called the palm
leaf skeletonizer.

Florida Agricultural Experiment Stations

All leaf miners hatch from eggs and pass through larval,
pupal and adult stages. Eggs are deposited upon the surface
or inserted into the leaf. The larva after hatching from the
egg finds its way into the leaf. It feeds there and passes through
several instars. Upon completion of the larval stage it passes
into the pupal or resting stage where it transforms to the adult.
Some species have but a single generation a year while others
may have several generations. Some forms require soft, tender
leaves and others attack mature leaves. Leaf miners are fairly
numerous, but due to their small size they do little harm to most
plants. There are a few notable exceptions and representative
forms are discussed.

Fig. 25.-Palm frond damaged by a palm leaf skeletonizer, Homaledra
sabalella (Chamb.). A larva, its injury and frass are shown in the lower

Caterpillar.-The palm leaf skeletonizer, Homaledra saba-
lella (Chamb.), probably is the pest most commonly encountered
on palms in Florida. Adults are tiny moths and are rarely seen.
Female moths lay their eggs on the young unfolding fronds.

Insect Pests of Ornamental Plants

The eggs hatch after several days and the young caterpillars
begin feeding immediately. They live gregariously in irregular
runways that are sheltered under a roof of brownish frass pellets
webbed together with silk (Fig. 25). Sometimes they fold the
fronds together and feed in this protected enclosure. Pupation
occurs on the leaf and there are several generations each year.
It injures saw palmetto, sabal, Phoenix and coconut palms.
Maggot.-The serpentine leaf miner, Liriomyza pusilla
(Meig.), is the most commonly observed and most widely dis-
tributed pest of the leaf miner group in Florida. The adult is
a black and yellowish fly about 1/20 inch long. Female flies insert
their eggs beneath the upper epidermis. These hatch after
several days into tiny yellowish maggots which begin feeding
immediately. At first the mine is very small but it gradually
widens as the larvae grow. The larva must obtain its nourish-
ment from a single leaf, since it is not able to enter a new leaf.
When full grown the larva usually leaves the mine to pupate.
There are several generations a year and in Florida the larvae
may continue their feeding through the winter.
Grubs.-Comparatively few beetles have developed leaf min-
ing habits. For the most part, these larvae confine themselves
to woody plants with thick, succulent leaves. Both the larval
and adult stages attack the foliage. However, the adults feed
on the upper surface and do not mine. The mines are chiefly
blister-like and, in cases of severe infestations, the leaves turn
brown as if scorched by fire. One species is a serious pest of
magnolias in some areas.
Control.-Leaf mining pests are extremely difficult to control
because they are protected from insecticides by the epidermal
surfaces of the leaves. In spite of this, applications of parathion
sprays generally have given excellent control. Use 15 percent
wettable powder parathion at the rate of 1 pound in 50 gallons
of water (1 ounce or 3 level tablespoons in 3 gallons). Frequently
additional applications, spaced at two-week intervals, are neces-
sary to prevent reinfestation. Sprays containing malathion have
given effective control. Applications of parathion and malathion
dusts give poor control of leaf miners.


The larvae of some beetles and moths which live in the woody
tissue of shade trees, palms and shrubs are called borers. They

Florida Agricultural Experiment Stations

are a constant threat to, and often serious pests of, ornamental
plants. Wilting leaves on individual twigs or stems often are
suggestive of their work. Borers also may cause an exudation
of sap and boring dust at the tunnel entrances. Infestations
usually start in weakened or dying plants and spread from these
centers. Recently transplanted dogwood and other trees and
shrubs are particularly susceptible to attack. Plants injured
by wind, fire, lightning or construction activities are often
weakened sufficiently to permit entrance by borers. Other causes
which tend to reduce the vitality of trees are the filling in of
earth and grading over of roots, drought and flooding.
There are two general types of borers. One group bores in-
dividual galleries and infests the plant in limited numbers at
widely separated intervals over the trunk and branches. Char-
acteristic examples of this group are the flatheaded apple tree
borer and carpenter worm. A second group is represented by
the shothole borers. These insects infest a plant in large num-
bers and many individuals are often found in the same gallery.
Sweet gum, dogwood and other shade trees which have been
translated recently are often infested with flatheaded borers.
Some species are bark borers and work primarily in the twigs,
while others attack scars and wounds and mine the sap or heart
wood of the trunk and branches. The adults are elongate-oval,
flattened beetles. They are a shining, dark metallic bronze color
above and somewhat lighter beneath. Usually the female lays
an egg near the end of a twig. After the egg hatches, the larva
enters the twig and tunnels downward toward the stem. The
yellow-white, legless larva is somewhat flattened and almost
an inch long when full grown. The larva pupates in an enlarged
place in the tunnel.
Caterpillars of some moths have habits similar to borers. One
of these is the carpenter worm which is a serious pest of live oaks.
The female moth has white wings mottled with gray and a wing
spread of three inches, while the male is somewhat smaller. The
body is rather stout and spindle-shaped. Eggs are laid in crev-
ices of bark, in wounds or in old tennels. The young larvae bore
through the bark and feed on the sapwood while the older larvae
feed in the heartwood. When full grown the caterpillar is white,
tinted with pink, and about 21/ inches long. Three to four years
are required to complete the life cycle.
The bark beetles are representative of the borers which at-
tack in numbers over the entire tree. Nearly all of the these

Insect Pests of Ornamental Plants

beetles are borers both as larvae and as adults. Pine trees struck
by lightning are usually attacked within a matter of days. When
these insects are present in numbers they will attack apparently
healthy trees. In general these insects burrow in the bark and
wood, although some species may discriminate as to the par-
ticular part of the tree they attack.
Control.-Control of borers in living trees is extremely diffi-
cult. Usually the condition is discovered too late to apply a
remedy and the larvae are well protected by the bark. In the
case of the first group of borers there are a number of remedial
measures which can be taken, while there are no effective means
of eliminating the second group.
Newly transplanted ornamental trees should be wrapped with
burlap or Spanish moss to prevent the adults from laying eggs
in wounds or other injuries. Infested twigs should be trimmed
out and burned. Fertilizer applied at about monthly intervals
and frequent watering will help to maintain plant vigor and to
some extent overcome attacks by borers.
Spraying infested trees with benzene hexachloride or DDT
is beneficial in reducing borer attacks. Apply 50 percent wet-
table powder DDT, at the rate of 2 to 4 pounds per 100 gallons
or 1 to 2 ounces in 3 gallons, to newly transplanted dogwood,
sweet gum, pine, oak, maple and locust trees. Twelve percent
benzene hexachloride (BHC) is used at the rate of 2 pounds per
100 gallons, or 1 ounce in 3 gallons. There is really no effective
means of controlling the borers known as bark beetles which
depend on a lowered vitality of the tree for successful attack.


Spider mites, commonly called "red spiders," are frequently
serious pests of most ornamental plants. They are not insects,
but are sufficiently like them to be considered here. Mites are
closely related to the spiders, ticks and scorpions, since they
have four pairs of legs. The name spider mite originated from
the fact that fine strands of silk similar to that of the spiders
are spun by many mites, although the webs may not be detected
Spider mites are extremely small and many of them are
1/50 inch or less in length. They are soft-bodied, oval-shaped
and colored yellowish, greenish or reddish. Many species are
so small that they cannot be seen without the aid of a micro-

Florida Agricultural Experiment Stations

Fig. 26.-Mite injury to camellia. Upper center and right and lower leaves
illustrate moderate to severe damage.

scope. Often their presence is not detected until they become
very numerous and cause obvious plant damage. Mites have
needle-like mouthparts with which they puncture the leaf and
suck up plant sap and chlorophyll. Withdrawal of the chloro-
phyll results in a russeted or stippled condition (Fig. 26) and
reduces the beauty and commercial value of the plant. Some
mite species restrict their feeding to a single host while others
are general feeders on a variety of plants. Although the mites
themselves may have disappeared from injured foliage, their
white shed skins, globular eggs or egg shells are usually present
to aid in identifying the injury.
The adult female mite lays three to five or more eggs a day
and may lay several hundred during her life. Eggs are laid
singly or in clusters. After hatching from the egg the immature

Insect Pests of Ornamental Plants 35

mite molts (sheds its skin) three times before reaching the
adult stage. The length of time required for the eggs to hatch
and for the development of the larval instars is influenced very
much by temperature. At about 800 F. many mites complete
their development from egg to adult in seven days. Plants
commonly found infested are African violet, asparagus fern,
azalea, camellia, camphor, chrysanthemum, Citrus sp., dahlia,
pyracantha, rose and viburnum. Almost all annual, perennial
and woody ornamental plants are subject to attack by one or
more species of mites. Some common mites are the cyclamen
mite, two-spotted mite, privet mite and purple mite.
Control.-Applications of oil emulsion (see under scale in-
sects) or sulfur dust are effective in controlling mites. Sprays
containing 2 pounds of 25 percent wettable powder malathion
in 50 gallons (1 ounce in 11/ gallons), 1 pound of 50 percent
wettable powder ovotran in 50 gallons (1 ounce in 3 gallons)
or 1 pound 50 percent wettable powder Kelthane in 50 gallons
(1 ounce in 3 gallons) are excellent miticides. Other materials
which have proved to be good miticides are demeton and para-


There are several creatures whose injury is negligible in most
instances but for which many inquiries are received and for this
reason they are included here.

Earwigs are readily recognized by the conspicuous pair of
pincers or forceps on the posterior end of the body (Fig. 27).

Fig. 27.-Earwig. The pincers at the posterior end of the body are not
poisonous. (About 3 times natural size.)

Florida Agricultural Experiment Stations

They are dark brown or black, small to medium sized about 3/4
to 1 inch long when adults, and have short wing covers. Earwigs
are largely nocturnal and occasionally are found at lights. Dur-
ing the day most of them are found in the soil or under mulch
and other debris in moist shady places. They are usually scaven-
gers and feed on decaying plant material, but also may feed on
animal matter. Reproduction and growth are very rapid and
occasionally they become a nuisance and constant worry to gar-
Benzene hexachloride (BHC), DDT and chlordane are par-
tially effective when applied as sprays or dusts.

Fig. 28.-Typical injury to rose foliage caused by leafcutting bees.

These solitary hairy wasps are medium-sized and usually
black or metallic blue or green in color. They have a curious
habit of making cells or nests for their young out of neatly cut
pieces of leaves. Rose foliage is used most often for this pur-
pose (Fig. 28). These circular and oval pieces of leaves are
used in forming the thimble-shaped cell. The cells are packed
away in isolated places. They are found in hollowed out stems
of pithy plants, in holes in wood and some times in neglected gar-
den hose. Usually several cells are placed end to end in a burrow.

Insect Pests of Ornamental Plants

Although rose foliage may show considerable evidence of
leafcutting bee activity, no control measures are suggested.

Snails and slugs are not insects. They are closely related
to oysters and clams. Snails have the body protected by a hard,
usually spirally-coiled shell, into which they retreat, while the
slugs are snails without the well developed hard shell. Usually
their color is a uniform gray or gray-black. The body is soft
and covered with a sticky mucous secretion. The individuals
usually observed range from 1 to 11/2 inches in length. Some-
times a small, gray snail develops in tremendous numbers and
becomes a nuisance.
Most snails and slugs feed at night, remaining concealed
during the day in dark, damp situations under boards or stones
and around compost. They move from place to place with a
gliding motion. Some species feed on leaves, stems or roots of
various plants and either scrape off the surface or make irregular
holes in the foliage. They are also objectionable because they
leave a characteristic slime trail wherever they go, which ren-
ders the plant unsightly and unsalable.
The development of snails and slugs is slow and gradual. Two
years are required for some species to reach maturity.
Control.-A metaldehyde bait, available at most garden sup-
ply stores, scattered about the infested area is most satisfactory.
When only a few slugs are involved, they can be collected at
night and destroyed. Some of the newer insecticides are effec-
tive in snail and slug control. A combination spray consisting
of 1 ounce (4 level tablespoons) 15 percent wettable powder
parathion plus an equal amount of a detergent in 3 gallons of
water has given good control in numerous instances. Applica-
tions of chlordane dust or spray provides some control. Apply
the insecticides after dusk for best results.

Millipedes are long, hard, wiry, sub-cylindrical creatures with
many body segments. Almost every segment bears two pairs of
small jointed legs. Sometimes they are called "thousand-legged
worms." The body is reddish brown to light tan in color. They
move rather slowly in spite of their numerous legs. When held
in the palm of the hand, they tend to roll themselves into a

Florida Agricultural Experiment Stations

spiral or coil. They live in dark, moist places and feed principally
on decaying plant material, but are known to attack sprouting
seeds or roots and bulbs.
Millipedes usually are considered only as a nuisance problem,
although there are exceptions to this general rule. They can
be controlled with either 5 percent chlordane, 1.5 percent ben-
zene hexachloride (BHC) or 1 percent parathion dusts.

The centipedes have the body flattened considerably and a
single pair of legs on each body segment. They are fast moving
creatures. Many of them live under bark of logs or under stones.
While they are not known to attack plants, centipedes should
be avoided as they have a pair of poison claws which are used
to kill insects for food.
Benzene hexachloride (BHC) applied as a 11/2 percent dust
or a spray consisting of 1 ounce (4 tablespoons) of 6 percent
gamma isomer BHC in 3 gallons of water provides some pro-
Sowbugs are chiefly scavengers, but occasionally they attack
the roots of plants. They are gray, oval and about 1/2 inch in
length. When held in the hand, they roll into a ball and appear
much like a miniature armadillo. Sowbugs are found most often
in damp situations such as under water-soaked boards. They are
nocturnal, remaining in dark places during the day. Under
favorable conditions the eggs hatch in about one month. De-
velopment is gradual, and several months to one year is required
to reach the adult stage.
Chlordane, benzene hexachloride (BHC), DDT and parathion
applied to the surface of the soil as sprays or dusts are effective

Chemicals used to control insects, mites and related pests
are called insecticides. Nearly all insecticides are poisonous to
humans and must be handled with extreme care. When not
being used they should be stored in places inaccessible to chil-
dren or pets, and preferably kept under lock and key.
For convenience the various types of insecticides are grouped
together as oil emulsions, chlorinated hydrocarbons, phosphatics
and systemics. In the past the chemicals were grouped, accord-

Insect Pests of Ornamental Plants

ing to their action on insects, as stomach poison and contact
insecticides. These older categories are no longer applicable
since the newer chemicals kill both by contact and as stomach
poisons. The older insecticides have been replaced largely as
the new organic chemicals have several advantages. The new
materials kill in several ways rather than only one and many
of them have long lasting or residual qualities. Usually they
kill rapidly, thus reducing the amount of insect damage. DDT
is probably the best known of the recent insecticides.
Insecticides are available in the form of dusts, wettable pow-
ders, emulsifiable concentrates, aerosols, baits, granules and
The major portion of an insecticidal dust is an inert filler
such as talc or lime. Dusts are prepared by mixing finely ground
particles of a solid insecticide with the filler or impregnating
liquid insecticides on the powdered diluent. Dusts are used as
obtained from the dealer. Dusts frequently are more desirable
than sprays for use on plants having dense foliage because
better distribution is obtained. Dusts also are immediately
ready for use and can be applied more quickly than spray.
Sprays are made by mixing wettable powders or emulsifiable
concentrates with water. Wettable powders contain the insecti-
cide plus a wetting agent, and when mixed with water form a
suspension of finely divided particles. Emulsifiable concentrates
contain the insecticide dissolved in an oil-type solvent, plus an
emulsifier which causes the oil and insecticide to mix well with
water. When emulsifiable concentrates are diluted with water,
the tiny droplets of oil become evenly dispersed through the
water. The emulsifier prevents the tiny oil droplets from
separating from the water and coalescing. They stay in suspen-
sion better and longer than wettable powders. Sprays usually
adhere to foliage better than dusts and are generally better to
use for hard-to-kill pests such as the scales and mites.
Aerosols have the insecticide dissolved in a liquefied gas
which is confined in a metal container. When pressure is re-
leased, the liquefied gas vaporizes and the fine particles of in-
secticide adhere lightly to the plant or other object treated.
Actually aerosols are sprays dispersed in extremely fine drop-
lets. The small spray bombs are convenient, clean and easy to
use. Aerosols are especially well suited for use in enclosed
areas. Most household aerosols are not designed for use on
living plants.

Florida Agricultural Experiment Stations

A fumigant is a highly volatile insecticide which acts upon
the insect as a gas. Fumigants are used only in confined areas
such as greenhouses and fumigation chambers, where the insecti-
cide can produce a toxic concentration of the vapor. Most of the
organic phosphate insecticides are volatile and have some fumi-
gation qualities. They are used principally as contact insecti-
Poison baits are prepared by mixing a poison with a material
which is attractive to a pest. Baits have been used extensively
for the control of a number of pests, but the newer insecticides
have largely replaced them. They are still recommended for
controlling mole-crickets, cutworms and slugs.
Considerable care should be used in the selection and applica-
tion of insecticides. Most of these chemicals when applied to
certain plants or used too strong will cause plant injury. Ac-
curacy of dosage is extremely important with the new insecti-
cides to minimize the danger of plant injury. If plant phyto-
toxicity is not known, it is wise to treat a few plants to determine
susceptibility prior to treating the entire planting. There are
so many different types of plants, and these in turn grow under
such varied conditions in Florida, that all of these problems
have not been worked out satisfactorily. The extent of plant
injury depends considerably on soil moisture, temperature and
humidity. Many plants are more susceptible to sprays when
they are wilted or near the wilting stage. Plants growing under
dry conditions should be irrigated thoroughly before you apply
insecticides to them. Observations also have indicated a ten-
dency for more plant injury to result from spray applications
made when temperatures exceeded 850 to 900 F. Much of this
injury can be avoided by applying sprays during the late after-
Oil emulsions for the control of scale insects ordinarily can
be used only during the spring and fall when there is but little
danger of temperatures exceeding 850 F. or falling below 42 F.
for two to three weeks following application. Oils cannot be
applied to tender growth without danger of plant injury. These
factors need not be considered with the new insecticides. For
example, parathion and malathion have advantages over oil
emulsion, because they can be used during the summer season
without danger of burning foliage. They can be applied with
more safety to tender foliage. They are more effective in many
instances and control a wider variety of insect species.

Insect Pests of Ornamental Plants

Failure to obtain satisfactory control of a pest often can be
attributed to improper application of the insecticide. The im-
portance of good and thorough application cannot be over-
emphasized. Apply the insecticides so as to obtain even distribu-
tion over the entire plant. Treat each plant systematically and
completely. Since most scale insect, mealybug, mite and white-
fly infestations are on the undersides of the leaves, the spraying
should be done with the nozzle directed upward.

Petroleum oils are used extensively as insecticides. The
highly refined or mayonnaise type oil emulsions are preferred
for use in horticultural sprays. Oil emulsions in prepared form,
ready to be diluted with water, are available from most insecti-
cide dealers and garden supply stores. Oil emulsions contain a
petroleum oil plus an emulsifier, such as soap, which aids in
getting the oil to mix readily with water. Most oil emulsions
contain 80 to 85 percent oil.
Oil emulsions should be used at 1 to 1.2 percent dilutions
(4 to 5 quarts per 100 gallons or 3 to 4 tablespoonfuls per gallon)
for the control of armored and soft scales, mealybugs, white-
flies and mites. The concentration used is dependent on the
type of plant to be treated, the severity of the insect infestation
and the time of year the application is made. In general, the
higher concentration is used on the following plants: camellias,
citrus, azaleas, gardenias, ixora, holly, ligustrum, pittosporum
and viburnum; while the lower concentration is used on hibiscus,
dogwood, turk's cap and rose. These strengths, although phyto-
toxic to tender succulent plants, are tolerated by most of the
woody ornamentals. Tender plants should be syringed off with
water about an hour following treatment with oil sprays.

World War II ushered in a new era in insect control. About
this time it was found that some of the synthetic organic com-
pounds, known as chlorinated hydrocarbons, were extremely
efficient in controlling a number of pests. The best known of
these materials is DDT. Many of these chlorinated hydrocarbon
materials kill insects by contact and as stomach poisons. In
addition, some give prolonged residual effects while others exert
a fumigating action under certain conditions. Thus the chlori-

Florida Agricultural Experiment Stations

nated hydrocarbons were unique among insecticides in having
a combination of important properties in that, they are both a
contact and a stomach poison; residues left on the plant may
remain effective for several weeks or longer; and they are effec-
tive at extremely low concentrations. A brief discussion of
some of the materials effective against ornamental pests follows.
DDT.-DDT is the short common name for dichloro-diphenyl-
trichloroethane. It is an excellent contact insecticide, and it
has residual qualities. It is very effective in controlling thrips,
leafhoppers, the adults and grubs of a number of beetles, and
many species of caterpillars. DDT is available as a 5 or 10
percent dust, 50 percent wettable powder, and 25 percent emulsi-
fiable concentrate. In general, the wettable powders are pre-
ferred for use in sprays, since less plant injury results from
applying sprays made with wettable powders than with emulsion
BHC.-Benzene hexachloride is another chlorinated hydro-
carbon insecticide which was developed shortly after DDT.
There is some objection to its use in that it has a persistent
pungent, disagreeable odor. Lindane is the common name given
to the essentially pure gamma isomer of benzene hexachloride.
Lindane has less odor than BHC and is used extensively for
controlling ornamental pests. It is an excellent contact insecti-
cide and controls aphids, leaf miners and a variety of caterpillars.
Chlordane.-Chlordane is similar to DDT in possessing a de-
gree of residual contact effectiveness against some insects. It
has not been used extensively on ornamentals. It is effective
against grasshoppers, mole crickets, earwigs, certain species of
caterpillars, and white grubs and other soil-inhabiting pests.
It is used as a 5 or 10 percent dust, a wettable powder or an
emulsifiable concentrate.
Other Chlorinated Hydrocarbon Insecticides.-Several other
chlorinated hydrocarbon insecticides are presently available.
These include aldrin, dieldrin, endrin, heptachlor and toxaphene.
Their effectiveness in controlling pests and phytotoxicity on
ornamentals has been determined in a few instances but not ex-
tensively. Additional testing of these materials is necessary
before they can be recommended. In general, they are not effec-
tive against the sucking insects, including aphids, whiteflies,
mealybugs, scale insects and mites.

Insect Pests of Ornamental Plants

During the past few years a group of insecticides known as
organic phosphates has appeared on the market. These insecti-
cides have given complete and thorough control of aphids, white-
flies, thrips, mealybugs, soft and armored scales, and mites.
They have advantages over the oils in that they can be applied
at any time of the year with less danger of phytotoxicity and
applications can be repeated frequently. They also can be ap-
plied to tender new growth. This is important, since biological
studies indicate that scale crawlers move out to the new growth
in numbers before "hardening-off" occurs.
Malathion.-Malathion is the approved common name of one
of the organic insecticides. It is closely related to parathion.
It is considerably less toxic than parathion to warm-blooded ani-
mals. There is no great hazard involved in handling this organic
phosphate material, and it is used extensively in the control of
ornamental pests. Malathion is effective in controlling aphids,
thrips, whiteflies, mealybugs, most soft and armored scales, a
number of caterpillars and mites. It can be applied without
danger of plant injury to a wide variety of ornamental plants.
It is available as a 4 to 5 percent dust, 25 percent wettable pow-
der and 50 percent emulsifiable concentrate. The latter is used
at 1 to 11/2 quarts per 100 gallons. For smaller quantities of
spray use 2 to 4 level tablespoonfuls of the wettable powder
per gallon, or 2 to 3 tablespoonfuls of the emulsifiable concentrate
per 3 gallons of water.
Parathion.-Parathion has proven to be one of the best in-
secticides yet developed to control the many pests plaguing the
flower grower. It gives excellent control of aphids, whiteflies,
mealybugs, scale insects, leaf miners and a wide range of other
insects and mites. It has the serious disadvantage of being ex-
tremely toxic to warm-blooded animals. Nurserymen and custom
spray operators, when applying parathion at frequent intervals
and for extended periods, should observe all the precautions
given on the label. Individuals who treat only a few plants at
a time and at widely spaced intervals are within the limits of
safety, since the quantity of the concentrate used is relatively
small and the exposure short and infrequent. It is available
as a 15 percent wettable powder and is used at rates of 1 to 2
pounds per 100 gallons or 1 to 2 level tablespoonfuls per 3 gallons.
Other Phosphatic Insecticides.-The insecticidal properties
of a number of other phosphatic compounds have been investi-

Florida Agricultural Experiment Stations

gated. Although some of these are effective in controlling insect
pests, they probably will not be used extensively on ornamentals
in the near future. Some of these materials are TEPP, EPN
and chlorthion. TEPP is excellent for controlling aphids, but
it is extremely toxic to warm-blooded animals and has no re-
sidual action. EPN controls mites effectively but is not effective
against a wide range of insects.
Caution.-Extreme care must be used when handling the
phosphatic insecticides. Avoid inhaling these materials. Any
material coming in contact with the skin should be washed off
immediately, since the phosphatics are absorbed through the
skin. The spray operator should stand to the windward side,
out of the drift of the spray particles, while making application
to avoid breathing any of the spray. When applying phosphatics
to a large number of plants involving the use of spray equipment
for a period of several hours, a respirator should be worn along
with rubber gloves and protective clothing. Unused lots of these
insecticides should be kept in tight containers and stored out
of the reach of children and pets, preferably under lock and key.
Empty containers should be disposed of by burying or burning.

A number of phosphatic compounds are readily absorbed by
growing plants and are translocated through the sap, making
all parts of the plant toxic to certain pests. Absorption may
take place through the roots, the foliage or the seed. Insecticides
absorbed into the plant are called systemics. Good control of
aphids, scale insects, mealybugs and mites requires thorough
and complete coverage with conventional materials. Systemic
insecticides have given excellent control of such pests and mini-
mized the problem of obtaining complete and thorough coverage.
In general, systemics are not effective against the chewing in-
sects. The systemics have been effective in controlling aphids,
mealybugs, whiteflies and mites when applied to the soil around
the base of the plant. Demeton was effective when applied by
means of a sprinkling can to individual plants, or to plants in
seed flats, and when applied through the overhead irrigation
Most systemic insecticides have long residual qualities. Some
systemics, when applied to the soil around the base of a plant,
are translocated into all parts of the plant as the plant develops.
Repeated applications of conventional insecticides are necessary

Insect Pests of Ornamental Plants

to effectively control aphids and mites on rapidly growing por-
tions of the plants. The use of systemic insecticides has elimi-
nated the need of repeating the application for controlling such
Many systemic materials are in the experimental stage. Due
to residues, systemic insecticides will be limited to use on orna-
mentals, nursery stock and non-food crops until the problem is
resolved. In general, future developments should produce ma-
terials toxic to a wider range of insects and mites. It now ap-
pears that the systemic insecticides are specific in their toxicity
to insects. The older insecticides when applied to the aerial
parts of a plant were non-selective and reduced the population
of beneficial insects as well as of the pests. Available data indi-
cate that the systemics are relatively non-toxic to parasites and
One systemic insecticide which has been approved for control
of ornamental pests is demeton. Demeton is available as a 22
to 23 percent emulsifiable concentrate in one gallon lots and is
used at rates of 1/ to 11/2 pints per 100 gallons.
Caution.-Observe the precautions given for the phosphatic
insecticides. There is no greater hazard involved in handling
the systemic materials than other insecticides of equal toxicity.


Various types of dusters and sprayers are available for apply-
ing insecticides. In general, there is but little variation in the
degree of control obtained with the different types of equipment
used to apply the insecticide. When and how the insecticides are
applied is important. One cannot over emphasize the necessity
of properly timing the application of the insecticide, or that
the correct amounts of dusts or sprays must be used. The dis-
tribution of the insecticide over the infested plant must be as
thorough as possible.

Hose Attachments.-Several sprayers which attach to the
garden hose (Fig. 29) are satisfactory for applying insecticides
as sprays. They are inexpensive and simple to use. Their use-
fulness is limited, since it is difficult to apply the spray to the
undersides of the leaves with this type of sprayer. Since many

Florida Agricultural Experiment Stations

Fig. 29.-Sprayers which attach to garden hose are suitable for con-
trolling aphids, chewing insects and mites but are not satisfactory for
applying sprays to control scale.

Fig. 30.-A 3-gallon compressed air sprayer is
a versatile all-purpose sprayer suitable for small

Insect Pests of Ornamental Plants

of the scale insects, aphids, whiteflies, thrips and mites live on
the lower sides of the leaves, these sprayers cannot be depended
upon for controlling these pests.

Fig. 31.-A 3-gallon knapsack sprayer, designed to be carried on the
back. The pump is operated with the right hand and the spray rod with
the left.

Compressed Air Sprayer.-The compressed air type of sprayer
(Fig. 30) is satisfactory for home gardeners. Most of these
sprayers have a capacity of two to four gallons. They are
equipped with an extension spray rod having a nozzle which can
be tilted to permit spraying the lower sides of leaves with rela-
tive ease. This type of sprayer is pumped up by hand before

Florida Agricultural Experiment Stations

spraying and has to be repumped when the pressure drops. Com-
pressed air sprayers must be shaken frequently to prevent the
insecticide from settling out, as they are not equipped with an
Knapsack Sprayer.-The usefulness of the knapsack sprayer
(Fig. 31) corresponds closely to that of the compressed air
sprayer. It is carried on the back and can be used to spray tall
shrubs and large plants effectively. The pump is designed to
maintain a higher and more uniform pressure than the com-
pressed air sprayer. The pump is operated with one hand and
the spray rod and nozzle with the other. Some knapsack spray-
ers have an agitator.

Fig. 32.-Power operated sprayer used extensively by the author in test
work. Note length of extension spray rod and hose.

Power Sprayer.-In general, power sprayers are more versa-
tile than hand sprayers and should be used when available.
Power operated sprayers are essential equipment for many

Insect Pests of Ornamental Plants

nurserymen, estates and park departments. A 15-gallon port-
able sprayer (Fig. 32) producing pressures of 150 to 200 pounds
per square inch was used in much of the experimental work on
which this bulletin is based. The sprayer was equipped with
a 75-foot lead of hose. The extension spray rod was five feet
long and equipped with two nozzles tilted at about 45 degrees
from the spray rod. Sprayers producing higher pressures are
seldom required except when treating tall trees.
There are many other types of power sprayers. Many of
them are designed to treat specific plants or crops but are flexible
enough to suit many requirements. Some nurserymen have
installed a large capacity power sprayer in a central location
in the nursery and have outlet pipes to all parts of the operation.
The system is designed to attach a lead of hose at various points
along the outlet pipe. By using different types of guns or vary-
ing the type, number and arrangement of nozzles they are able
to satisfactorily treat various types of plants.


Fig. 33.-Insecticidal dusts are quickly and easily applied to a limited
number of plants with this midget hand duster.

Midget Hand Duster.-There is a small hand duster (Fig. 33)
on the market which has proven useful for applying insecticidal
dusts in a variety of situations. It is simple to operate and
dusts can be applied quickly and efficiently with it. For the

Florida Agricultural Experiment Stations

most part, its use is restricted to small areas. Distribution is
fairly uniform and excessive applications can be avoided. This
duster should be adequate for applying insecticides for control-
ling mealybugs, aphids, thrips, lacebugs and caterpillars. It
is suitable for small gardens.

Fig. 34.-Crank-type rotary hand duster with the cover to dust
hopper raised.

Crank-Type Rotary Duster.-The crank-type rotary hand
duster (Fig. 34) is satisfactory for both small and large gardens.
It is best suited for use on close growing crops. It delivers a
continuous stream of dust and is especially useful in lath houses.
Power Duster.-Power dusters, like power sprayers, are best
suited to commercial florists and nurserymen.
Each grower should consider his particular needs and consult
with authorities concerning the type of equipment most likely
to fill his requirements.


The author wishes to express his appreciation to a number of persons
and concerns who aided in various ways to make this bulletin possible. Dr.
A. N. Tissot, Entomology Department, gave encouragement and valuable
suggestions that aided immeasurably in undertaking the work. He also
reviewed the manuscript and made many helpful criticisms. Dr. S. H.
Kerr, Entomology Department, and Mr. Ralph Dickey, Horticulture De-
partment, reviewed the manuscript and made many valuable suggestions.

Insect Pests of Ornamental Plants

Mr. F. A. Robinson, Entomology Department, made many of the photo-
graphs used as illustrations.
A number of nurserymen offered encouragement, made many useful
suggestions and supplied a number of plants used in the tests. Samples
of the insecticides used in the control tests were supplied by the following
manufacturers and formulators: American Cyanamid Company, Cali-
fornia Spray-Chemical Corporation, Florida Agricultural Supply Company,
Chemagro Corporation, Geigy Agricultural Chemicals, Shell Corporation
and Velsicol Corporation.


1. EBELING, WALTER. Subtropical Entomology. Lithotype Process Co. 1950.
2. KUITERT, L. C. Control of insect pests of camellias. Amer. Camellia
Yearbook, 147-155. 1949.
3. Parathion controls some of the insect pests of woody
ornamentals. Proc. Fla. State Hort. Soc. 1949.
4. Use of demeton (Systox) for controlling insects on
ornamentals. Proc. Fla. State Hort. Soc. 66: 321-324. 1954.
5. MERRILL, G. B. A revision of the scale-insects of Florida. State Plant
Board of Florida Bul. 1. 1953.
6. PRITCHARD, A. EARL. Greenhouse pests and their control. Cal. Agri.
Exp. Sta. Bul. 713. 1949.


The publications in this collection do
not reflect current scientific knowledge
or recommendations. These texts
represent the historic publishing
record of the Institute for Food and
Agricultural Sciences and should be
used only to trace the historic work of
the Institute and its staff. Current IFAS
research may be found on the
Electronic Data Information Source

site maintained by the Florida
Cooperative Extension Service.

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of Florida

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