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Detection and Identification
of Insects and Related Pests
of the Commercial Foliage Industry
R. A. Hamlen, D. E. Short and R. W. Henley
Florida Cooperative Extension Service
Institute of Food and Agricultural Sciences
University of Florida, Gainesville
John T. Woeste, Dean for Extension
DETECTION AND IDENTIFICATION OF INSECTS AND
RELATED PESTS OF THE COMMERCIAL
R. A. Hamlen, D. E. Short and R. W. Henley*
Insects and mites are a major cause of tropical foliage plant
losses to growers and retailers, and their presence on plants
constitutes a nuisance to the consumer.
Establishment of control programs during production and
after sale requires basic knowledge of these pests' life cycle.
It is important to know how the pest was introduced into the
greenhouse or retail shop, how it spreads, and its relative rate
Since pesticides are so often required, it is necessary to decide
on the most effective chemical to use, what formulation is best,
the correct dosage rate, and the proper method, as well as the
time and frequency of application. Major emphasis must be given
to selection of pesticides safe for the crop and the people who
may come in contact with treated plants. Specific pesticide
recommendations will not be discussed herein because they fre-
quently change. For current recommendations and information
on safety of pesticides to foliage plants refer to the Florida
Insect Control Guide or Plant Protection Pointer -52, "Pest
Control Guide for Commercial Foliage and WVoody Ornamental
Plants in Florida" and Plant Protection Pointer 757, "Phyto-
toxicity of Insecticides and Miticides to Foliage and Woody Or-
namental Plants," published by IFAS, University of Florida,
Production and maintenance of quality foliage plants depends
on people recognizing the most common insect, mite and other
pests that infest tropical foliage plants and knowing how they
develop and what can be used to control them.
Select Specific Pesticides
Before discussing the specific pests themselves, a comment on
types of pesticides available may aid in understanding why
specific pesticides are selected for controlling particular pests.
*Assistant Professor of Entomology, ARC Apopka; Associate
Professor Estension Entomologist, University of Florida,
Gainesville; Associate Professor, Extension Foliage Specialist,
A major consideration is that both cultural conditions and types
of plants grown in the foliage plant industry are so varied that
no single pest control program can be suggested. One possible
program is the application of maintenance or preventive sprays
at one to three week intervals, depending upon the pest, crop
and the length of pesticide residue. Such a program should kill
most of the initial pest invaders and prevent pest populations
from further development.
Maintenance of relatively pest-free stock, propagation and fin-
ishing areas is far easier than eradication of pests once they
become well established in large populations. Where a preventive
program is not followed, it is essential to inspect plants closely
at weekly intervals to detect initial pest populations, and once
found, to apply effective control measures before pests reach
Systemic pesticides usually provide the most effective control
of pests that feed by sucking plant sap (aphids, mealybugs,
scales and whiteflies). Systemic pesticides applied as sprays enter
the plant and are transported to the leaves and stems. Thus,
when an insect punctures and feeds on sap of a plant treated
with a systemic, it receives a lethal dose of the chemical. Sys-
temics are of particular advantage when pests are covered by
foliage and are therefore inaccessible to pesticides that kill only
Spray Both Sides
In the application of pesticides both leaf surfaces, especially
the lower side, must be covered by the spray. Systemic activity
of the pesticide is no excuse to justify poor spraying techniques.
A spreader-sticker should be added to the spray solution to insure
proper coverage and retention of the pesticide on foliage. This
is especially important if plants are watered overhead, as this
method quickly washes pesticides off the foliage if a sticker is
lacking. Where mites are troublesome, miticides, (chemicals with
activity directed specifically against mites) should be used.
Some systemic emulsifiable concentrates are effective when
applied as soil drenches. However, never apply soil drenches to
plants under water stress as plant injury is likely to result. Some
pesticides are available as granular systemic insecticides, miti-
cides and nematicides and have been highly effective against
sucking insects and mites.
To correctly apply systemic granules, the recommended weight
of granules must be distributed over specific soil surface areas
of containers, benches or beds. One quarter to 1/ inch of water
should follow to flush the chemical off the granules and into the
root zone where it can be absorbed and translocated to the upper
plant parts. They usually provide effective control for one to
Pesticide Can Damage Plants
Phytotoxicity is a term used to define plant injury often caused
by pesticides. Damage to foliage often appears as marginal burn,
chlorosis, spotting and distorted or abnormal growth. Although
any portion of the plant may be affected, the new growth is most
likely to show damage. In the use of soil drench applications, root
tissue may be injured causing stunting or slow plant decline.
To minimize phytotoxicity, pesticides should be applied during
the cooler parts of the day. Application should be made in the
early morning in order that the foliage will be dry before tem-
peratures reach 850 to 900F. Generally, wettable powders are less
phytotoxic than emulsifiable concentrate sprays; however, wet-
table powders often leave objectionable residues on foliage.
Since some plants are more easily injured by certain insecti-
cides, it is advisable to make three or four preliminary sprays
Fig. 1. Apical leaves of the zebra plant infested with wingless adult
females and nymphs of the green peach aphid.
at weekly intervals to several plants under actual growing en-
vironments, before proceeding to treat an entire crop. If com-
binations of chemicals are to be used in a single spray, be es-
pecially careful to make preliminary treatments. Since there may
be several formulations of a chemical compound labeled for
market with different concentrations of the active ingredient,
recommendations on the manufacturer's label should be fol-
Aphids are small (generally less than 1/8 in. long), soft-bodied
sucking insects which feed on young developing leaves and stems,
causing distorted or stunted plant growth (Fig. 1). Their body
color is quite variable, most commonly including green, yellow
or black forms. Alert nursery personnel can often detect their
white skins shed on older leaves which are frequently the first
indication of an aphid infestation.
Multiplication rate of aphids, when uncontrolled is enormous.
When aphid populations become overcrowded, winged forms may
be produced and disperse to begin new infestations. Many grow-
ers first notice an infestation on plants adjacent to greenhouse
vents or evaporate cooling pads because these are the locations
where aphids frequently gain entry. Winged forms caught in air
currents may be rapidly spread throughout a greenhouse. The
initial source of these aphids may be partially eliminated by
strict sanitation and weed control both outside and inside the
Aphids excrete a sticky honeydew which coats the infested
foliage. This honeydew is ideal for growth of black sooty-mold
fungi rendering the affected plant unsightly and unsalable.
Control is usually achieved by a single, properly applied spray,
drench or granular treatment. Occasionally, reinfestations occur
and a second spray application may be necessary after four to
six weeks. Specific crops often found infested include: Aphelan-
dra, Brassaia, Gynura, Hoya, and Dieffenbachia.
Caterpillars are immature forms (larvae) of moths and are
often referred to as armyworms, loopers or cutworms. These in-
sects actively feed on and damage a wide range of foliage plants.
Infestations can occur when adult moths fly into greenhouses
from outdoor areas.
Fig. 2. Injury by small caterpillars on Peperomia. Feeding removes
the undersurface leaf tissue and produces a "window" effect (W) in the
Fig. 3. Adult fungus gnat. Notice the delicate pair of wings, many
segmented antennae and long legs.
Fig. 4. Black-headed fungus gnat larvae (1) and pupae (p) found
in infested soil.
Initial infestations are difficult to detect as newly hatched
larvae feed on the superficial tissues of the lower leaf surfaces. As
the feeding larvae remove the undersurface layers of leaf tissue,
a "window" effect is produced on the leaf surface, a condition
commonly observed with Brassaia seedlings and Peperomia (Fig.
2). Only after larvae grow to 1 to 11/2 inches do they actually
begin to consume entire leaves.
Caterpillars are chewing insects and are susceptible to contact
or stomach poison insecticides and are unaffected by most granu-
lar systemics. Exclusive use of granular systemics often allow
larval populations to increase to the point where severe losses
occur. It is much easier to suppress infections if controls are
applied when caterpillars are small.
Although larvae are general feeders, specific crops found to be
occasionally infested include: Asparagus, Brassaia, Cissus, Dief-
fenbachia, Maranta, Peperomia, Philodendron and various orna-
mental Cactaceae and Crassculaceae.
Foliage growers and retailers frequently become concerned
about tiny "black flies" which can become abundant under green-
house and indoor plant conditions. These flies often are fungus
gnats and represent a potential threat. The 1/8 inch long adult
fly (Fig. 3) is a weak flier and is most visible near or on the soil
surface or under leaves. The immature legless form, a black-
headed larvae is about 1/ inch long and lives in the soil (Fig 4).
The larvae have been associated with feeding on and decay of
plant roots and lower stem tissues. Highly organic soils of high
moisture content appear to enhance infestations, especially in
the presence of decaying plant tissue. Feeding may be particular-
ly injurious to seedlings, rooted cuttings or young plants. Con-
trols are usually directed against the larval stages by applica-
tions of chemical drenches to infested soils.
These are soft-bodied insects about 1/8 inch long and possess
a covering of fuzzy, white, waxy threads. Although there are
various types that attack foliage, the longtailed, solanum and
citrus mealybugs are most troublesome.
As with aphid infestations, affected foliage most often is
coated with honeydew and sooty-mold fungi. Adults and nymphs
(young) tend to clump on affected foliage making it difficult for
Fig. 5. Infestation of solanum mealybugs on the purple passion vine.
Note clumping of individuals and the waxy accumulations.
Fig. 6. Root mealybug infestation of bromeliad roots. Notice the
cottony-like, egg-containing masses (m) and nymphs (n) located along
insecticides to penetrate the waxy deposits that surround them
(Fig. 5). For this reason, systemic chemicals are often more
effective than contact insecticides.
Reproduction is continuous in greenhouses, consequently it is
important to make several insecticide applications at intervals
of approximately 14 days. Systemic drench and granular insec-
ticides are also effective. Frequent hosts are: Aphelandra, Ardi-
sia, Asparagus, Crassula, Croton, Cryptanthus, Dieffenbachia,
Dizygotheca, Dracaena, Epipremnum (Scindapsus), Ficus, Gynura,
Hoya, Maranta, Nephrolepis and Syngonium.
In addition to foliar mealybugs, several mealybug species live
below the soil surface and feed on root tissue. This small, below
ground pest is often overlooked until infestations are severe
and widespread. In commercial production and in retail opera-
tions plants frequently should be removed from containers and
their roots inspected.
White Masses Contain Eggs
If root mealybugs are present, a careful examination of roots
may reveal white, cottony-like masses which contain eggs and
females (Fig. 6). Root mealybug nymphs are active and may
crawl from pot to pot via drainage holes or be spread in irriga-
tion water. Populations may become established in soils be-
neath infested plants, forming a source of reinfestation to fol-
To eradicate this pest, be sure to sterilize all soil, pots, and
tools and destroy any infested plants which have not responded
to previous insecticide applications. Clean bench and potting
areas, apply effective insecticide drench treatments to stock
plants and practice strict sanitation in the future. Granular in-
secticides are also effective when care is given to uniformly apply
the proper amount over the soil surface before watering.
Specific crops frequently infested include: Araucaria, Aspar-
agus, Chamaedorea, Chlorophytum, Chrysalidocarpus, Cordyline,
Dieffenbachia, Dizygotheca, Epipremnum (Scindapsus), Ficus,
Hedera, Hoya, Nephrolepis, Pilea, Peperomia, Philodendron,
Syngonium, Zygocactus and various bromeliads.
The two-spotted spider mite is the most common and destruc-
tive mite on tropical foliage plants. This mite is small, about
1/50 inch long, may be brown, greenish or orange-red, is eight-
Fig. 7. Spider mite infested foliage of parlor palm. Note the web-
bing, speckling of upper leaf surfaces due to feeding and the mass of
mites (m) at the leaf tip in position for dispersal.
legged and hardly visible to the unaided eye even when full
grown. You will need a 10X or greater magnifying glass to
readily see them and populations often become quite large before
they are detected.
Most nursery personnel readily recognize this pest when it
produces webs over the foliage, especially on the new leaves
(Fig. 7). Mites feeding on the underside of leaves produce a
greyish or yellowish speckling which is especially prominent
when viewing the upper leaf surface. In severe infestations and
leaf injury, and especially under low humidity indoor conditions,
affected leaves become dry and drop off.
A point of importance in understanding this pest's habits in
the greenhouse and indoors is its dispersal mechanism. When
numbers of mites and subsequent competition for food increase,
mites congregate in an organish mass at the apex of the plant,
typically at the tip of the apical leaf (Fig 7). Individual mites
then drop on silken threads, forming a "rope" of living mites.
Spread to new plants can then occur by air movement, on clothes
or by cultural operations. Once this dispersal phase begins, severe
and irreversible damage has usually occurred resulting in an
unsalable crop and introductions of mites into other areas.
Mites Develop Resistance
Miticides should be applied a minimum of two times at a five
to seven day interval to allow for egg hatch between applications
so that both adults and individuals that hatch from eggs are
killed. If a miticide is properly applied and is not providing con-
trol, change to another miticide because mite populations easily
develop resistance to most chemicals.
Table 1 includes several examples of miticides listed according
to their chemical classification. Growers must learn from experi-
ence which chemicals, when correctly applied, fail to give satis-
factory control, and to then try other nonchemically related
miticides in a different classification.
Table 1. Classification of miticides according to chemical
I. Chlorinated Hydrocarbons: dicofol (Kelthane)
II. Sulfones Sulfonates: tetradifon (Tedion)
III. Sulfites: propargite (Omite)
IV. Cyclic Carbonate: oxythioquinox (Morestan)
V. Carbamates: aldicarb (Temik)
VI. Organotin: Plictran, Vendex
Often, a severe mite problem occurs on plants in the retail
shop because a few mite eggs or nymphs survived even the best
and most conscientiously followed control program during pro-
duction. It is imperative, therefore, that a miticide be applied to
major mite host plants as close to the date of shipment as pos-
Apply Miticide Before Marketing
The retailer might also consider applying a miticide to major
mite host plants prior to placement into retail operations. Major
hosts of this pest are: Brassaia, Calathea, Chamaedorea, Chrysali-
docarpus, Cissus, Codiaeum, Cordyline, Dieffenbachia, Dracaena,
Fatshedera, Fatsia, Hedera, Maranta, and Polyscias.
Other than the spider mite, several microscopic, injurious
mites also have been repeatedly detected on foliage plants. The
most important of these appear to be the broad and cyclamen
mites. These mites are translucent and so small, about 1/100
inch long, that their presence is usually first detected by the plant
injury symptoms rather than by visual observation. Symptoms
of injury initially include the appearance of new leaves that are
curled or cupped, smaller than usual (Fig. 8), newly produced
Fig. 8. Infestation of cyclamen mites on Pilea. Notice the cupped,
thickened and dwarfed leaf development.
Fig. 9. Inhibition of leaf expansion (ie) due to broad mite infesta-
tion of English ivy.
smr ? .'
Fig. 10. Apical leaves of zebra plant infested with broad mites.
Note the serrated margins (sm) of developing leaves.
Fig. 11. Killing of the shoot apex (a) following severe broad mite
infestation of the zebra plant.
Fig. 12. False spider mite infested foliage of the lipstick plant
showing mite injured (mi) basal areas of affected leaves.
Fig. 13. Florida red scale infesting leaves of English ivy.
leaves that do not expand (Fig. 9) or the development of leaves
with serrated margins (Fig. 10). Heavy infestations often cause
death of the shoot apex (Fig. 11).
The false spider mite, another microscopic mite, is reddish in
color and heavy infestations produce a bronze or reddish dis-
coloration on basal areas of affected leaves (Fig. 12). Damage
by this pest has been especially serious on Aphelandra, Columnea
and ornamental cacti.
These preceding small mites are readily moved about on in-
fested plants, equipment or nursery personnel. Injury caused by
these tiny pests is often mistaken by growers, florists and con-
sumers for spray injury or cultural mismanagement and, there-
fore, effective controls are often not applied. As with the spider
mite, repeated applications of an effective miticide on a five
to seven day interval is advised.
Scales are usually small even when mature (1/16 to 1/4 inch
diameter). They occur in many different shapes and colors. Some
common examples are Florida Red Scale (Fig. 13), False Ole-
ander Scale (Fig. 14), Hemispherical Scale (Fig 15), Soft Brown
Scale (Fig. 16), and Japanese Wax Scale (Fig. 17). Scales are
Fig. 14. Heavy infestation of false oleander scale on areca palm. Note the
female (f) scales on upper leaf surfaces.
Fig. 15. Foliage of the zebra plant infested with hemispherical
scale. These are all females and notice their location along veins on
the underside of affected leaves.
Fig. 16. Soft brown scale infesting Pteris fern.
Fig. 17. Stem infestation by Japanese wax scale on Podocarpus.
initially inconspicuous and by the time an infestation is noted,
the population is usually so great that the plant is unsalable.
Once again, the enormous amounts of honeydew excreted by cer-
tain scales allows the prolific growth of sooty mold.
Eggs, produced beneath a relatively hard female shell, hatch
into translucent crawlers, the only stage usually not covered by
a relatively hard covering. Crawlers move over new foliage to
locate feeding sites, usually on or near veins on the underside
of leaves (Fig. 15). The crawler stage is practically invisible to
the unaided eye making it nearly impossible to detect new in-
festations on cuttings or other propagation material. It is also
at this stage that introduction of scales into production areas
occurs. Consequently, it is imperative to maintain stock areas
Quarantine New Plants
It is wise to quarantine newly acquired plants and, if careful
examination shows living scales present, apply effective insecti-
cides until the infestation is eliminated.
To check for living scales, lift the female scale shell using
the point of a knife. If it is firmly attached to the plant, or if
the top cover pops off revealing a yellow-organish, plump mass
attached to the leaf surface, consider the scale alive. Dead female
scales, however, may contain living eggs that will produce
crawlers. Use at least a 10X hand lens to look for the miniature
"jelly bean-like" eggs beneath the empty female shell.
Chemical control is difficult because of the shell-like body of
the females which protects both feeding scales and eggs from the
toxic chemicals. Sprays or drenches of systemic insecticides are
effective when correctly applied. Sprays may need to be repeated
at two to three week intervals. Continue to check for living scales,
especially on new foliage, keeping in mind that scale populations
are slow to respond to treatment and they breed constantly in
the greenhouse. Therefore, persistence in treatment and careful
observation of results will be required to bring success.
These small (about 1/16 inch), slender, gregarious, active
insects feed by rasping or shredding plant tissue surfaces with
their mouth parts. Tissue around feeding punctures dries out,
giving a silver-flecked appearance to wounded areas (Fig. 18).
Larvae are frequently pale yellowish and highly active. Adults
are often darkly colored and are able to jump when disturbed.
Fig. 18. Thrips feeding injury to Ardisia foliage. Notice the silver-
flecked appearance of affected leaves.
Fig. 19. Adult white flies congregating and feeding on the under-
side of infested, recently developed foliage.
Thrips feed primarily on young tissue in the bud or shoot
apexes where new leaves are expanding. Heavy infestations often
result in noticeable deposits of dark fecal material on infested
leaf surfaces. Once again a keen eye and the frequent use of a
good hand lens may avoid expensive losses. Repeated insecticide
sprays at seven to ten days have been effective. Primary hosts
are Aphelandra, Ardisia, Brassaia, Dieff enbachia, Ficus, Philo-
dendron, Sanse cieria, and Syngonium.
This pest is most noticeable when infested plants are moved.
The winged adults which collect in vast numbers on the upper
or young foliage take to the air producing a miniature "snow-
storm" (Fig. 19). Immature whiteflies produce enormous
amounts of honeydew. Greenhouse infestations more than often
occur through the introduction of infested plants or by migra-
tion of winged adults from infested areas outside of the green-
house. Again, inspect newly received plants and remove all
extraneous plant material from in and around your operation.
In controlling this pest the adults are easily killed, but the
remaining stages usually continue to develop and produce more
adults. It is, therefore, advisable to apply an insecticide re-
peatedly at a seven to ten day interval for three to four weeks.
Systemic granules, when applied properly, may control white-
fly for periods up to two months.
Whiteflies are an important and most persistent pest of orna-
mentals, particularly poinsettia, and also infest bedding plants
such as ageratum, fuchsia and salvia. However, this pest is of
only occasional importance on foliage plants unless grown in
accompaniment with a major whitefly host.
SLUGS AND SNAILS
Slugs (Fig. 20) have soft, unsegmented bodies, exude a slimy,
sticky, mucous-like substance and have the ability to elongate
and contract their bodies. Snails (Fig. 21) are related to slugs
but possess a shell within which the body can be retracted when
disturbed. Both are almost universal pests in greenhouses. In-
troductions into production areas may occur in soil, or on pots
and trays previously stored on the soil, or invasion may occur
from outside vegetation. They are omnivorous and voracious
feeders, using rasping mouthparts, with immature ones feeding
on surface tissue and larger individuals eating irregular holes
in foliage (Fig. 21). As feeding is often nocturnal and individuals
Fig. 20. Slug feeding on the lower leaf surfaces of the zebra plant.
Note the unsegmented body and the absence of a shell.
^y~ws 'P -
Fig. 21. Injury to Fittonia from snail (S) feeding. Notice the
presence of a shell.
are hidden in moist, dark areas, such as under fats or pots
during the day, damage is often blamed on cutworms or other
Sprays or baits may be used for control. Best results are
usually obtained if the baits are applied in the afternoon and
avoiding irrigation until the next day. As feeding is often inter-
mittent and eggs are unaffected, repetitive applications are
necessary for control of all developmental stages. Good sanita-
tation with the removal of extraneous vegetation and trash piles
or other material which might offer food or shelter to these
pests will aid in the effectiveness of the control program.
Single copies are free to residents of Florida and may be obtained
from the County Extension Office. Bulk rates are available upon
request. Please submit details of the request to C.M. Hinton, Publi-
cation Distribution Center, IFAS Building 664, University of
Florida, Gainesville, Florida 32611.
COOPERATIVE EXTENSION WORK IN AGRICULTURE AND HOME ECONOMICS
(Acts of May 8 and June 30, 1914)
Cooperative Extension Service, IFAS, University of Florida
and United States Department of Agriculture, Cooperating
K. R. Tefertiller, Director
This publication was printed at a cost of $516.45 or 17 cents per copy
to inform commercial foliage growers about the detection and identi-
fication of insects and related pests of foliage plants.