Front Cover
 Acknowledgments and approaches...
 Individual problems
 Approaches to the control of citrus...
 Precautions in the use of...
 Back Cover
 Four keys to pesticide safety

Group Title: Circular - Florida Cooperative Extension Service - 139G
Title: Control of insects, mites and diseases of Florida's dooryard citrus trees
Full Citation
Permanent Link: http://ufdc.ufl.edu/UF00067881/00001
 Material Information
Title: Control of insects, mites and diseases of Florida's dooryard citrus trees
Series Title: Circular Florida Cooperative Extension Service
Physical Description: 27 p. : ill. ; 23 cm.
Language: English
Creator: Knapp, Joseph L
Publisher: Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida
Place of Publication: Gainesville
Publication Date: 1980
Subject: Citrus -- Diseases and pests -- Florida   ( lcsh )
Genre: government publication (state, provincial, terriorial, dependent)   ( marcgt )
non-fiction   ( marcgt )
Statement of Responsibility: Joseph L. Knapp.
General Note: Cover title.
Funding: Circular (Florida Cooperative Extension Service) ;
 Record Information
Bibliographic ID: UF00067881
Volume ID: VID00001
Source Institution: Marston Science Library, George A. Smathers Libraries, University of Florida
Holding Location: Florida Agricultural Experiment Station, Florida Cooperative Extension Service, Florida Department of Agriculture and Consumer Services, and the Engineering and Industrial Experiment Station; Institute for Food and Agricultural Services (IFAS), University of Florida
Rights Management: All rights reserved, Board of Trustees of the University of Florida
Resource Identifier: oclc - 08851322

Table of Contents
    Front Cover
        Page 1
    Acknowledgments and approaches to the control of citrus pests
        Page 2
    Individual problems
        Page 3
        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
    Approaches to the control of citrus pests and suggested spray program
        Page 20
        Page 21
    Precautions in the use of pesticides
        Page 22
        Page 23
        Page 24
        Page 25
        Page 26
        Page 27
    Back Cover
        Page 28
    Four keys to pesticide safety
        Page 28
Full Text


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.

Copyright 2005, Board of Trustees, University
of Florida

ril 1980 r- Circular 139 G
1 Revision of no.

control of Insects, Mites and Diseases
of Florida's Doorvar trusS- Tees
L A i 'Y

Florida Cooperative Extension Service
Institute of Food and Agricultural Sciences
University of Florida, Gainesville
John T. Woeste, Dean

The use of trade names in this publication is solely for the purpose of
providing specific information. It is not a guarantee or warranty of the
products named and does not signify that they are approved to the
exclusion of others of suitable composition.

This publication was prepared in cooperation with research ento-
mologists and plant pathologists of the Institute of Food and Agricul-
tural Sciences and USDA. Numerous workers made suggestions and
helped in obtaining and preparing photographs.

1. Do Not Apply Pesticides. (See page 20 .) There are many in-
stances where dooryard, and even commercial plantings of citrus
are never sprayed or dusted, and yet the trees survive and produce
good crops of satisfactory fruit. This results from natural control of
pests by parasites, predators, weather, and other factors.
2. Individual Problems Controlled When They First Appear.
(See page 20 .) This requires learning to identify common citrus
pests and detecting their presence early enough so that sprays can
be timed to give effective control. Most homeowners find this prac-
tice to be unsatisfactory.
3. Follow the Spray Program Suggested in This Circular. (See
pages 20-21.) This practice is generally more satisfactory than
Number 2 for those who use pesticides.

Joseph L. Knapp1
Insects, mites, and diseases are common problems to the Florida
homeowner with a dooryard planting of citrus. The object of this
circular is to aid him in the control of these pests.
Frequently more harm than good comes from an attempt to control
these pests with pesticides. To be successful, the right material
should be applied at the right time using the right amount in the
right manner. If any of these conditions cannot be met, it is usually
better not to spray at all.
In order to acquaint the home citrus grower with insects, mites,
and diseases and their control, the subjects are discussed in the
following order: individual problems; beneficial insects, mites, and
fungi; approaches to the control of citrus pests; dooryard pest control
chart; suggested spray programs; sprayers; and precautions in the
use of pesticides.

Citrus rust mites (Fig. 1) have an annulate, wedge-shaped body
lemon-yellow in color and about 1/200 inch in length. They have 2
pairs of legs and piercing-sucking mouthparts. They can just barely
be seen with the naked eye and can be seen better with a 10-power
magnifying glass.

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Figure 1 Citrus rust mites.
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The life cycle of the citrus rust mite is completed within 5-7 days
during the summer. Eggs are spherical (round), transparent and laid
singly on leaves, stems and fruit of all commercial citrus varieties.
The mite has 2 immature stages that are similar to the adult in
appearance. Although present throughout the year, in Florida the
citrus rust mite is most prevalent during the summer months.
Injury from extensive citrus rust mite feeding causes surface
blemish to the fruit (Fig. 2). This can reduce the external quality of
marketable fruit, and reduce yield by causing premature fruit drop
and reduced fruit size. At times, citrus rust mite feeding will cause.
premature leaf drop.

Figure 2 Rind blemish caused by citrus rust mites.
Citrus red mites (purple mites) (Fig. 3) are only about 1/50 inch
long. They are bright red to deep purple in color and infest leaves,
fruit, and new growth. Injury results from feeding and appears as a
scratching or etching of fruit and the upper surface of leaves. In
periods of prolonged dry weather they can cause a collapse of leaf
cells and even leaf drop. Use a 10X magnifying glass to inspect for
citrus red mites and eggs on the upper surface of the leaf, looking
especially along the midrib as well as in angular crevices of the leaf
stems and the young, tender twigs. Citrus red mites are more
numerous from May through July, but can be the most damaging
from October through February.

'Extension Citrus Pest Management Specialist

Figure 3 Citrus red mite.

Texas citrus mites are about the same size as citrus red mites,
but are brownish-green in color with dark brown to greenish spots or
bars near the lateral margins (edges). Numbers of mites are
generally much heavier along the midrib on the upper surface of
leaves. They also are most numerous May through July, and most
damaging October through February.
Six-spotted mites are also about the same size as citrus red mites
but are white-yellow to sulfur-yellow in color. Adults usually have
six dark spots that are barely visible with a 10-power magnifying
glass, arranged in two rows on the back or abdomen. These mites live
in colonies on the under surface of leaves, especially along the veins
and midribs. Injury appears as yellow spots, often cupped toward the
top of the leaf. Six-spotted mites prefer grapefruit, but can be found
occasionally on other varieties of citrus. They usually appear in early
February and have disappeared by mid July.
Purple scale (Fig. 4) and Glover scale (long scale) are very
similar in appearance and habits, but Glover scale is longer and
narrower. The covering of the mature scale is purplish-brown in color
and about Y~ inch long. These scales suck juices from leaves, fruit,
twigs and branches. Injury to leaves results in yellow or chlorotic
spots. These scales can cause leaves and fruit to drop, as well as cause
twigs and branches to die. They are often overlooked because they
are found primarily on the inner parts of the tree.



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Figure 4 Purple scale.

Chaff scale (Fig. 5) forms a light brown nearly round armor
closely resembling a piece of wheat chaff. Where abundant on the
bark, the limbs appear to be covered with chaff. This scale infests
leaves, fruit and bark, causing green spots on the fruit.
leaves, fruit and bark, causing green spots on the fruit.

Figure 5 Chaff scale.

Citrus snow scale (Fig. 6) is a serious pest in most parts of citrus
growing areas of Florida. Male scales have elongated white armor,
while females are mahogany colored, making them inconspicuous
and hard to see against tree bark. They are largely confined to the
trunk, limbs and twigs.
If its parasite is not active in your area and chemical control is
necessary, make 2 applications of the recommended insecticides at
the times given in the Suggested Spray Program. Be sure to
thoroughly wet all bark.

Figure 6 Citrus snow scale on tree trunk and limbs.

Florida Red scale (Fig. 7) and Yellow scale (Fig. 8) are armored
scales of similar size and shape. The armor or covering of the adult
female is almost circular in outline for both scales; however, the
yellow scale is yellow to light orange in color, while Florida Red scale
is dark reddish-brown with a nipple-shaped center that is grayish to
reddish-yellow. These insects infest leaves and fruit, and can cause
them to drop.
Do not mistake Florida Red scale for brown whitefly fungus.
Cottony cushion scale (Fig. 9) is rarely of economic importance
except in nurseries and on young trees. The mature female is
conspicuous because of her fluted white egg sac. The Vedalia
ladybeetle feeds on this scale and usually keeps it under control, but
cannot always be depended upon on young trees.


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Figure 7 Florida red scale.

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Figure 8 Yellow scale.





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Figure 9 Cottony cushion scale.
Whiteflies (Fig. 10), which primarily attack new growth, are
disliked by most dooryard growers. The nymph (immature stage),
which is transparent and seldom recognized, infests the underside of
the leaves, withdrawing copious quantities of sap, resulting in some
injury to the trees. Dooryard growers also object to sooty mold fungus
(Fig. 11) which in turn grows in the honey-dew excreted by the
immature stages of the whitefly. Never spray the trees when a large
number of adult whiteflies are present.Instead, wait 10 to 12 days
until most of the adult whiteflies have disappeared. This will allow
enough time for the eggs to hatch and the young to be killed before
they can cause much damage.
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Figure 10 Whiteflies.

Figure 11 Sooty mold fungus.

The citrus blackfly is a close relative of the common whitefly
often seen in Florida. The adult fly is about 1/25 of an inch long, slate
blue-black in color. Eggs are laid in a distinctive spiral pattern
(Fig. 12) on the underside of leaves with about 28 to 34 eggs in each
spiral. The larvae change from dusky color through dark brown to
black as they grow. The pupae are shiny black, spiny and oval in
shape. Homeowners should look for this insect on the underside of
leaves and report suspected infestations to the local county
Extension office.


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Figure 12 Citrus blackfly egg spirals and immature forms.

Mealybugs (Fig. 13) have a segmented body which is covered with
mealy white wax. They are most common during the spring and
early summer, but are frequently found during the winter in tree
crotches and under loose bark. Mealybugs may become so numerous
following fruit set that their feeding under the button of young fruit
may cause the fruit to drop. They also collect in masses between fruit
clusters. Sooty mold can also be severe following a mealybug

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Figure 13 Citrus mealybug.

Aphids or plant lice (Fig. 14) attack young, tender growth and
cause leaves to wrinkle and curl (Fig. 15). Insecticides should be
applied to infested young growth before the leaves curl. There is
little value in applying an insecticide after many leaves are curled or
new growth is nearly mature.
The orange dog (Fig. 16) is often a pest of young citrus trees. As
an adult, the species is a large black and yellow swallowtail
butterfly. However, it is named from the larva, which is an ugly
brown and white caterpillar which grows to a length of 1'/, to 2
inches. During the summer and early fall these caterpillars may be
quite destructive on young trees. Pick caterpillars off young trees by
Several kinds of grasshoppers and katydids (Fig. 17) feed on the
leaves of citrus trees, but usually are not important pests of dooryard

trees. Eggs of the broad-winged katydid are laid along the leaf
margins and arouse the interest of many home gardeners.

Figure 14 Aphids or plant lice.

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Figure 15 Leaf curl caused by aphid feeding.


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Figure 16 Orange dog larvae.

Figure 17 Broadwinged katydid.

There are many beneficial parasites (tiny wasp-like insects),
predators (insect and mite) and pathogens (predominantly fungi)
that attack various pests of citrus. In many cases, natural enemies
regulate potential pests. This is referred to as biological control.

Parasitic wasps. Many wasp-like parasites, particularly of the
genus Aphytis, effectively control a wide range of armored and soft
scale pests. Most noteworthy are the parasites of purple, Florida Red
scale, and the citrus snow scale (Fig. 18).

pure 18 Scale parasites shown by scale for size comparison.

Fungi. Two parasitic fungi, Aschersonia spp. and Aegerita sp. are
commonly found infecting immature whiteflies of citrus. Red
Aschersonia forms pink and reddish pustules Ys inch or less in
diameter on the underside of leaves (Fig. 19). It is so colorful that
many growers are quite concerned when it appears and usually think
it is harmful. Aegerita or brown whitefly fungus appears as
cinnamon pustules about Ys inch in diameter on the underside of
leaves. This fungus is often confused with Florida Red scale.

Figure 19 Aschersonia fungus infecting whiteflies.

Other fungi such as Hirsutella thompsonii (Fig. 20) and
Triplosporium floridana attack citrus rust mite and Texas citrus
mite, respectively. H. thompsonii is particularly important in
reducing citrus rust mite populations in the summer.
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mite infected by Hirsutella

Figure 20


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Figure 21 Ladybeetle adults feeding on aphids.

Predators. Several insect and mite predators such as the
ladybeetles, adult (Fig. 21) and larvae (Fig. 22); and lacewings,
larvae (Fig. 23), feed upon eggs and other stages of insects and mites.
Most are general in their feeding habits and exhibit an overall effect
on pests throughout the year.

Figure 22 Ladybeetle larvae.



Figure 23 Lacewing larvae feeding on aphids.

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Scab (Fig. 24) is a fungus disease that attacks young leaves, small
fruit and tender twigs of grapefruit, Temple, Murcott honey orange,
lemons, sour orange, Satsumas, and some varieties of tangelos. It
causes raised, light brown, corky areas on fruit and leaves (Table 1).


Figure 24 Scab on temple orange.

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Figure 25 Melanose on 'Marsh' grapefruit.

Melanose (Fig. 25) is a fungus disease that attacks young fruit
primarily of grapefruit; however, other citrus varieties may be
affected. The injury to fruit is often confused with rust mite injury,
which has a smoother feel. This rind blemish does not affect the
quality of the fruit. While scab is more important on young trees,
melanose is more injurious to older trees. Trees are usually over 10
years of age before melanose becomes a problem. Since melanose
grows in dead wood, keeping the trees free of such wood will aid in
the control of this disease (Table 1).
Greasy spot (Figs. 26 and 27) is a fungus disease that attacks all
varieties of citrus grown in Florida. Infection occurs mostly in the
summer, but symptoms do not appear until two to nine months later.
Symptoms first show up as yellowish-brown spots on the leaves. The
spots develop a slightly blistered appearance on the underside of the
leaves, and ultimately become oily brown or black. Spots vary in size
from small dots to u% inch in diameter.Where several spots coalesce
(grow together), the areas covered may be considerably larger. This
disease can cause serious premature defoliation during the fall and
winter. This disease may also infect the fruit rind, especially on
grapefruit, causing specks to appear in areas between the oil glands.
Good spray coverage of the lower leaf surface is essential for
satisfactory control (Table 1).

Figure 26a Greasy spot on upper lef surface.
Left ely infection. Right -late infection.


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Figure 26b Greasy spot on lower leaf surface.
Left early infection. Right late infection.

Figure 27 Greasy spot on grapefruit.

Sooty mold (Fig. 11) may blacken leaves of the entire tree.
Aphids, mealybugs, certain soft scales, and particularly immature
whiteflies excrete a sweet, syrupy material known as honey-dew. The
sooty mold fungus grows wherever this material falls. Controlling
these insects will prevent sooty mold, and oil sprays will usually
cause it to flake off, making leaves and fruit bright and shiny.

Homeowners with a few citrus trees should follow one of the
following courses in the control of insects and diseases:
1. Do not apply pesticides. Depend entirely on natural control of
predaceous insects and mites, parasitic insects and diseases,
weather, and other factors. There are many instances where
dooryard, and even commercial plantings are never sprayed or
dusted, and yet the trees survive and produce good crops of
satisfactory fruit. Under this program, yield may be reduced and
external quality will usually be low.
2. Individual problems controlled when they first appear.
(See Pest Control Chart, page 24 .) Make frequent inspections,
identify the problems, and apply the recommended pesticides before
infestations can become severe. These steps require: 1) learning to
identify the more common pests of citrus; 2) detecting their presence
early; 3) sprays timed to give effective control. Unfortunately, most
homeowners do not find this practice easy to follow and the results
are often unsatisfactory. Frequently the pests cause severe damage
before they are detected. (Cooperative Extension Service Circular
137-D, Insects and Mites of Florida Citrus, will give additional help
in learning to identify citrus pests.)
3. Follow the spray program suggested in this circular. This
schedule may need to be supplemented in the event insects such as
grasshoppers, katydids, and other less common pests attack citrus
trees between the regular sprays.

There is no simple rule one can follow which will always result in
bright fruit and vigorous trees. However, there is a rather simple
spray schedule that can be followed which will control most pests and
result in thrifty trees producing fruit of good quality, but not
necessarily always of a bright color. A schedule of this type usually
requires three or possibly four spray applications per year. A
suggested spray program follows. (Substitutions can be made see

Postbloom (4 weeks after petals fall) Copper plus a recommended
Summer (JuneJuly) Benlate plus Ethion plus .5% spray oil.
Fall Recommended miticide for citrus rust mite and spider mite

Figure 28 Compressed air sprayer.


Many of the failures to control citrus pests that are charged
against the pesticide are quite often the result from improper
application and timing. A gardener who has a substantial number
of citrus trees is advised to get a good sprayer. One to three-gallon
compressed air models (Fig. 28) can be used while trees are small.
These models are not expensive. Air pressure is pumped up by hand,

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and the nozzle, which is at the end of a short wand, delivers a fine
spray which can be accurately directed to all surfaces.
When trees become large and cannot be thoroughly covered by this
type of sprayer, dooryard citrus growers should either obtain a small
power sprayer or hire someone with adequate equipment to insure
thorough coverage of the entire tree. If these conditions cannot be
met, it is generally better not to apply sprays at all.
Sprayers which attach to the end of garden hoses are generally not
satisfactory for use on mature citrus trees. The spray pattern is
usually coarse, and it is very difficult to direct the spray to reach and
adequately cover the undersides of the leaves, especially those near
the ground, and the side of plants close to a building or fence. If a
hose attachment sprayer is used, the emulsion concentrate
formulation of insecticide is preferred over the wettable powder.

Care in Handling Pesticides. Treat all pesticides as poisons
and handle according to the cautions on the manufacturers' product
labels. Always read the label carefully and completely before using
any pesticide.
Pesticide Residues. Citrus consumed by the producer should be
prepared by the generally accepted practices of washing, peeling, etc.
Dooryard fruit that is offered for sale must conform with federal
and/or state food and drug pesticide residue regulations. Copper and
oil emulsions are exempt from a tolerance, and no waiting period is
required. Waiting periods between last application of certain
pesticides and harvest of fruit are as follows: Benlate no time
limitation; Diazinon 21 days; Ethion 21 days on lemons and limes;
no time limitation on orange, grapefruit, tangelo, tangerine; do not
repeat application within 90 days; Kelthane -7 days; malathion 7
Oil Emulsion Sprays. Do not apply oil emulsion sprays during
the fall or winter months or to a tree that shows signs of wilting. Two
oil sprays a year are not recommended, but if applied, allow at least 6
weeks to elapse between applications. Do not mix oil with sulfur or
apply the two separately without allowing at least a three-week
interval between applications, as injury to fruit and foliage may
Herbicides (weed killers). Another problem that should be of
concern to dooryard citrus growers is the use of weed killers on
lawns. If a weed killer is used, be sure it is not used close enough to
citrus to result in residues in the fruit; or be sure it is approved for
use around citrus trees.

Household Sprays. Several homeowners have made the
mistake of spraying citrus trees and other plants with sprays
formulated specifically for use inside homes to control household
pests. These sprays, in general, have the insecticide dissolved in
some type of petroleum solvent such as refined (deodorized) kerosene
and should not be applied to plants because injury to the plants
usually results.

Table 1. Dooryard Citrus Pest Control Chart

Other Pests
Controlled Remarks



Ethion + oil



Rust mites
Spider mites
Rust mites
Spider mites
Grasshoppers & katydids
Spider mites
Greasy spot
Loosens sooty mold

Controls citrus snow scale only
Controls citrus snow scale only

Controls most species of scale insects

Does not control chaff scale

Does not control snow scale. Do not
apply if trees are wilting or in a near
wilt state. Do not apply within 3 weeks
of sulfur. Oil applied after October may
increase susceptibility of trees to cold
damage and may reduce crop the
following year. Oil applied in the fall
may inhibit solids formation and retard
fruit coloring.

Spider mites
Citrus snow scale




Rust Mites


Ethion + oil


Most species of scale insects
Spider mites
Spider mites

Spider Ethion Rust mites
Ethion + oil Rust mites
Most species of scale insects
Kelthane Rust mites
Oil Scale See comments under scale pests
(Does not control citrus
snow scale)
Greasy spot
Loosens sooty mold

Aphids Malathion Mealybugs
Grasshoppers & katydids



Grasshoppers & katydids


Other Pests
Controlled Remarks

Whiteflies Oil Scale
Spider mites
Greasy spot
Loosens sooty mold
Malathion Scale

Grasshoppers Malathion Scale
& katydids
Mealybugs, aphids,

Scab Copper Apply before new growth starts in the
fungicide spring and when 2/3 of petals have
spray fallen



Scab Apply spray thoroughly to young fruit,
4 weeks after the flowers shed.




Greasy spot

'Read the label thoroughly follow label directions for mixing and application rates.

This public document was printed at a cost of $998.90, or 19.9 cents per copy to inform home gardeners
about citrus insects, mites and disease. 5-5M-80

SCIENCES, K. R. Tefertlller, director, in cooperation with the United States Department of Agriculture, publishes this Infor-
mation to further the purpose of the May 8 and June 30, 1914 Acts of Congress;and Is authorized to provide research, educa- IFAB
tional Information and other services only to individuals and institutions that function without regard to race, color, sex or
national origin. Single copies of Extension publications (excluding 4-H and Youth publications) are available free to Florida
residents from County Extension Offices. Information on bulk rates or copies for out-of-state purchasers is available from
C. M. Hinton, Publications Distribution Center, IFAS Building 664, University of Florida, Gainesville, Florida 32611. Before publicizing this
publication, editors should contact this address to determine availability.

June-July. Sprays of copper may
blacken existing corky areas of the
rinds, but this will not affect eating
See comments under scale pests

Four Keys to Pesticide Safety


TAINER BEFORE EACH USE. Heed all cautions and

LABELED CONTAINERS, away from food or feed.
Keep them out of the reach of children, pets, and irre-
sponsible people.









Four Keys to Pesticide Safety


TAINER BEFORE EACH USE. Heed all cautions and

LABELED CONTAINERS, away from food or feed.
Keep them out of the reach of children, pets, and irre-
sponsible people.









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