Title: Control of insects and diseases of dooryard citrus trees
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Permanent Link: http://ufdc.ufl.edu/UF00084386/00001
 Material Information
Title: Control of insects and diseases of dooryard citrus trees
Series Title: Control of insects and diseases of dooryard citrus trees
Physical Description: Book
Creator: Brogdon, James.
Publisher: Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida
 Record Information
Bibliographic ID: UF00084386
Volume ID: VID00001
Source Institution: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
Resource Identifier: oclc - 232333819

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

June 1972



SEP 1 1972

-tk IA

-' -- --

James E. Brogdon
Fred P. Lawrence
R. S. Mullin


41~14 yi,


1. Do Not Apply Sprays or Dusts. (See page 14.) There are
many instances where dooryard, and even commercial plant-
ings 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. Control Individual Problems When They Appear. (See page
14.) This requires learning to identify the common pests of
citrus and being able to detect their presence early enough
so that sprays can be timed to give effective control. Most
homeowners do not follow this practice satisfactorily.

3. Follow the Spray Program Suggested in This Circular. (See
pages 14, 15, 16.) This practice is generally more satisfactory
than Number 2 for those who use pesticides.

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 workers of the Uni-
versity of Florida Agricultural Extension Service, Experiment Stations,
and College of Agriculture; USDA; and industry. Numerous workers
made suggestions and helped in obtaining and preparing photographs.
Special appreciation is expressed to W. L. Thompson, R. B. Johnson and
R. F. Brooks, Citrus Experiment Station, Lake Alfred, and L. W. Ziegler,
College of Agriculture, for assisting in the preparation of this circular.

First Printing 1955
Second Printing 1965
Third Printing 1966
Fourth Printing 1968
Fifth Printing 1969
Sixth Printing 1971
This Printing 1972

(Acts of May 8 and June 30, 1914)
Cooperative Extension Service, University of Florida and United States
Department of Agriculture, Cooperating, Joe N. Busby, Dean



James E. Brogdon, Fred P. Lawrence, and R. S. Mullin1

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 these conditions cannot be ob-
served, it is usually better not to spray at all.
In order to acquaint the home citrus grower with insects and
diseases and their control, the subjects are discussed in the fol-
lowing order: individual problems; beneficial insects, mites, and
fungi; approaches to the control of citrus pests; dooryard pest
control chart; suggested spray programs; sprayers; and precau-
tions in the use of sprays.

Purple scale (Figure 1) and Glover scale (long scale) are
very similar in appearance and habits, but long scale is longer

S" ,.

Figure 1.-Purple scale on leaf.
Much enlarged.

Figure 2.-Purple and long scale on
twigs and leaves.

1Entomologist, Citriculturist and Plant Pathologist.

and narrower. The covering of the mature scale is purplish-
brown and about 1/8 inch long. These scales suck juices from
leaves, fruit, twigs and branches (Figure 2). Injury to leaves
results in a yellow or chlorotic area or spot. These scales can
cause leaves and fruit to drop, and twigs and branches to die.
They are often overlooked because they are found primarily on
the inner parts of the tree.
Chaff scale (Figure
3) forms a light brown
nearly round armor.
Where abundant on the
bark, the limbs appear
to be covered with chaff. -
This scale infests leaves,
fruit and bark. It causes
green spots on the fruit.
Citrus snow scale
(Figure 4) is a serious
pest in parts of Orange, "
Seminole, Volusia and
Lake counties. Male Figure 3.-Chaff Scale.
scales have elongated
white armor, while fe-
males are inconspicuous
and hard to see against
tree bark. They are
largely confined to the
trunk, limbs and twigs.
Control of snow scale
is difficult. Make 3 appli-
cations of the recom-
mended insecticides at
the times given in the
Suggested Spray Pro- Figure 4.-Citrus Snow Scale.
gram. Be sure to thoroughly wet all bark. Recent experiments
have shown diazinon also to be effective against snow scales at
the rate of 2 teaspoons of diazinon 2E per gallon of water (1 pint
in 50 gallons).
Florida red scale (Figure 5 and 6) and Yellow scale (Figure
7) are armored scales. The armor or covering of the adult female
is almost circular in outline for both scales, but yellow scale is
lighter in color. It is yellow to light orange, 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,



Figure 6.-Grape-

fruit with heavy red
scale infestation. .

and ma y cause
them to drop.
Florida red
scale may be mis-
taken for brown
whitefly fungus.

Figure 5.-Florida
red scale on leaf.
Much enlarged.

A .

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Figure 7.-Yellow



Cottony cushion scale
(Figure 8) is rarely of
economic importance ex-
cept on young trees. The
mature female is con-
spicuous because of her
fluted white egg sac. The
Vedalia ladybeetle feeds
on this scale and usually
keeps it under control,
but cannot always be de-
pended upon on young

Figure 8.-Heavy infestation of cottony
cushion scale on young citrus twig. Young
scale shown on leaf.

Whiteflies (Figure 9) are disliked by most dooryard growers.
The nymph (immature stage), which is seldom recognized, in-
fests the underside of the leaves and withdraws quantities of
sap, resulting in some injury to the trees. Dooryard growers

object to sooty mold
fungus (Figure 24)
which grows in the hon-
ey-dew given off by the
immature stages of the
whitefly. (See page 12.)
Never spray the trees
when a large number of
adult whiteflies are seen,
but wait 10 to 12 days
after most adult white-
flies have disappeared.
This will give the eggs
time to hatch and allow
the young to be killed
before they cause much

^ .a, ^ 2. '

1. I

Figure 9.-Whiteflies on a citrus leaf.

Mealybugs (Figure 10) have
a segmented body which is
covered with mealy white wax.
They are most common during
spring and early summer, but
are frequently found during
winter in tree crotches and
under loose bark. Mealybugs
may become so numerous fol- Figure 10.-Citrus mealybugs
lowing fruit set that their feeding under the button of young
fruit may cause fruit to drop. They also collect in masses be-
tween fruit clusters. Sooty mold (Figure 24) is also severe
following a mealybug infestation.

Aphids or plant lice (Figure 11) attack young, tender growth
and cause leaves to wrinkle and curl (Figure 12). 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.


Figure 11.- Non- i
winged adult aphids
and some young. -

Figure 12.-Young citrus leaves severely curled
by aphids. Note aphids. Also note ladybeetles
which feed on aphids.

The orange dog (Fig-
ure 13) is often a pest of
young citrus trees. As an
adult, the species is a large
black and yellow butterfly.
The larva is an ugly brown
and white caterpillar which
grows to a length of 11/. to
2 inches. During the sum-
mer and early fall these
caterpillars may be quite
destructive on young trees.
Figure 13.-Orange dog cater- Pick caterpillars off young
pillar on citrus twig. trees by hand.

Several kinds of grasshoppers and katydids (Figure 14) feed
on the leaves of citrus trees, but usually are not important pests
of dooryard trees. Eggs of the broad-winged katydid are laid

Figure 14.-Top-broad-winged

katydid. Bottom-lubberly grasshopper.

along the leaf
margins (Figure
15) and arouse
the interest of
many home gar-
deners. If grass-
hoppers and
katydids become
numerous enough
to require insec-
ticidal control, Figure 15.-Eggs of the broad-winged katydid
apply malathion on leaf margin.
at 2 teaspoons of 57% malathion emulsifiable concentrate per
gallon of water (1 pint in 50 gallons).

Citrus red mites (purple mites) (Figure 16) are only about
1/50 inch long. They are rose to deep purple and infest leaves,
fruit, and new growth. Injury appears as a scratching or etch-
ing of the upper surface of the
leaf. They may cause a collapse
of leaf cells and leaf drop. Use ";
a magnifying glass to inspect t -
for purple mites and eggs on ,
the upper surface of the leaf,
especially along the midrib and
in angular crevices of leaf stems
and young, tender twigs. Purple
mites are more numerous from
May through July, but are most
injurious from October through
Feb Figure 16.-Purple mite and egg
February. greatly enlarged
Texas citrus mites are about the same size as purple mites,
but are brownish-green with dark brown to greenish spots or
bars near the lateral margins. Populations of mites are much
heavier on the upper surface of the leaves. They are most nu-
merous May through July, but most damaging October through
Six-spotted mites are about the same size as purple mites
but are white-yellow to sulfur-yellow. Adults usually have six

dark spots 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 are found on other types of citrus. They usually
appear in February and disappear by the middle of May.
Rust mites (Figure 17) are present most of the year. Their

Figure 17.-Rust mites magnified about 20 to 25 times.

injury (Figure 18), which
does not materially affect in-
ternal fruit quality, often re-
sults in russet (brown) fruit
and may cause leaf drop.
They appear as tiny yellow
wedges about 1/200 inch long.
They cannot be seen with the
naked eye and are difficult to
recognize with a 10-power
magnifying glass. Look for
mites on green fruit and both
sides of leaves.

Figure 18.-Rust mite

injury to fruit.

Scab (Figure 19 and 20) 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


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varieties of tangelos. The disease is particularly important in
coastal areas. It is a serious problem on young trees where
it causes raised, light brown,
corky areas on fruit and
leaves. Scab can be controlled
with two copper sprays. The
first should be applied just
before growth starts in the
spring and the second when
two-thirds of the petals have
fallen from the bloom.
Melanose (Figures 21 and
22) is a fungus disease that
attacks young leaves, small
fruit, and tender twigs. The
diseased leaves have raised
brown lesions that make them
feel like sandpaper. The in-
jury to fruit is often confused
with rust mite injury, which Figure 19.-Scab on young citrus
has a smoother feel. While leaves.
scab is more important on young trees, melanose is more injuri-
ous to older trees. Trees are usually over 10 years of age before
melanose becomes a
problem. Melanose can
be controlled by coating
the young fruits, leaves,
and tender twigs with a
ccoplper spray just after
S'. the flowers shed (usually
," in early April). Since
.7 q- melanose grows in dead
I wood, keeping the trees
free of such wood will
aid in the control of this
.. disease.
Greasy spot (Figure
23) first causes yellow-
ish brown spots on one
side of the leaves, later
becoming visible on both
sides. The spots then
Figure 20.-Warty areas and protuber- have a slightly blistered
ances of the rind caused by scab on young appearance on the under-
fruit of lemon. side of the leaves, and
the color ultimately becomes an oily chestnut brown. Spots

vary in size from small dots to i. inch in diameter. Where
several spots coalesce, the areas covered may be considerably
larger. The disease may cause leaves to drop.
Use of copper in the post-bloom spray and zineb or oil emul-
sion in the summer spray will aid in controlling greasy spot.

". S

Figure 21.-Melanose of grapefruit, Figure 22. Distortion of
showing raised brown to black colored young grapefruit leaves as a re-
pustules. suit of severe melanose infection.

Sooty mold (Figure 24)
may blacken the entire tree.
,0. Aphids, mealybugs, certain
soft scales, and particularly
immature whiteflies excrete
a sweet, syrupy material
S-. known as honeydew. This
&4V material falls on leaves and
-.. "- fruit, and in it grows sooty
m mold fungus. Controlling
4 i, these insects will prevent
i sooty mold, and oil sprays
S "will usually cause it to flake
-r.- off, making leaves and fruit
bright and shiny.
Nutritional Problems
Nutritional or physiolog-
ical sprays are very im-
Figure 23.-Greasy spot on citrus portant and necessary for
leaves. portent and necessa for
citrus growing in alkaline
soils. Many growers find these sprays beneficial to all citrus
regardless of soil acidity or fertilizer practice.

A good nutritional spray is one that contains copper, zinc,
and manganese. Since neutral materials are easier to mix and
use, they are recommended to homeowners in preference to the
sulphate compounds. Mixing directions on the label should be
followed, since neutral copper, zinc, and manganese are available
in formulations containing several different percentages of me-
tallic copper, zinc, or manganese.
Apply nutritional sprays in
the spring before growth starts,
usually between January 15 and r
February 15, or add them to the
Post-Bloom Spray. (See page

There are many beneficial
parasites (tiny wasp-like in- Figure 24.-Sooty mold on
sects) and predators (insects grapefruit.
and mites) that feed on the various pests of citrus. There are
also two important fungus diseases that kill immature whiteflies.

Figure 25.-Four kinds of ladybeetles that
may be found on citrus.

Ladybeetles (Figure
25) are small, beneficial
insects. Some are black
with two red spots, and
others orange with sev-
eral or no black spots.
Both the young and
adults feed on harmful
Red aschersonia, com-
monly found on citrus
trees, is a beneficial

fungus that kills immature whiteflies. It forms pink and
reddish pustules 1/8 inch or less in diameter on the underside of
leaves. It is so colorful that many growers are quite concerned
when it appears and usually think it is harmful.
Brown whitefly fungus also aids in control of whiteflies. It
appears as cinnamon or brownish pustules about 1/8 inch in di-


ameter on the underside of leaves. This fungus is often con-
fused with Florida red scale. However, it can be distinguished
from red scale because it does not have the raised reddish-brown
center peculiar to the red scale.

Homeowners with a few citrus trees should follow one of the
following courses in the control of insects and diseases:
1. Do not use sprays or dusts. Depend entirely on natural
control by predaceous insects and mites, parasitic insects and
diseases, weather, and other factors. There are many instances
where dooryard, and even commercial plantings are never spray-
ed 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. Control individual problems when they appear. (See Pest
Control Chart, page 16.) Make frequent inspections, identify
the problems, and apply the recommended pesticides before in-
festations become severe. These steps require learning to iden-
tify common pests of citrus and being able to detect their pres-
ence early enough so that sprays can be, timed to give effective
control. Unfortunately, most homeowners do not follow this
practice satisfactorily. Frequently the pests cause severe dam-
age before they are noticed. (Agricultural Extension Service
Circular 137, Insects and Mites of Florida Citrus, and Circular
200, Control of Minor Pests of Commercial Citrus, will give ad-
ditional help in learning to identify citrus pests.)
3. Follow the spray program suggested in this circular.
This schedule may need to be supplemented if 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 re-
sult 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 four or possibly five
spray applications per year. A suggested spray program follows.
(Substitutions can be made-see chart.)

1. Post-Bloom Spray (March-April).-This spray should be
applied immediately after the flower petals have fallen and be-
for the young fruits are 3 inch in diameter. This usually occurs
in late March or early April. A suggested combination spray
follows. Amount of Pesticide
50 Gals. Water 1 Gal. Water
Malathion (57%) emulsifiable concentrate 1 pint 2 teaspoons
Kelthane (18/2%) emulsifiable concentrate 1 pint 2 teaspoons

NOTE: A neutral copper should be used (a) for melanose con-
trol on older trees; (b) for scab control on Temple, Satsuma,
grapefruit, tangelos, Murcott honey orange, and lemons; and (c) to
aid in greasy spot control. Follow directions on amount on the
container label, since available formulations of neutral copper
contain different percentages of metallic copper. Nutritional
materials can be added to this spray. (See Nutritional Problems,
page 12.)

2. Pre-Summer Spray (May).-Same as Fall Spray below.

3. Summer Spray (June 15-July 15).-A suggested combina-
tion follows.
Amount of Pesticide
50 Gals. Water 1 Gal. Water
Oil Emulsion (80-90% oil) 3 pints 2 tablespoons
Ethion (25%) emulsifiable concentrate 1 pint 2 teaspoons

4. Fall Spray (Between October 15 and November 15).-A
suggested combination follows.
Amount of Pesticide
50 Gals. Water 1 Gal. Water
Malathion (57%) emulsifiable concentrate 1 pint 2 teaspoons
Kelthane (182%) emulsifiable concentrate 1 pint 2 teaspoons

5. Dormant Spray (Usually in January).-This is an optional
spray and may be omitted unless scab is a problem (on Temple,
Satsuma, grapefruit, tangelos, Murcott honey orange, and lem-
ons) or mites or scales show signs of building up to high popu-
lations. Neutral copper should be used for scab, Malathion for
scales, and Kelthane for mites. To these can be added nutritional
materials. (See Nutritional Problems, page 12.)


Pests Material Amount Remarks
Scales (except Malathion 2 teaspoons per gallon Cover upper and lower surface of all leaves and branches
cottony-cushion), (57%) EC, (1 pint in 50 gallons) thoroughly. For citrus snow scale, thorough cover of
Whiteflies Ethion 2 teaspoons per gallon the trunk, limbs and twigs is essential. See Suggested
(25%) EC (1 pint in 50 gallons) Spray Program. See cautions in the use of oil sprays.
plus plus
Oil emulsion 2 tablespoons per gallon
(80-90%) (3 pints in 50 gallons)
Cottony-cushion Malathion 2 teaspoons per gallon A second application usually will be needed, 3 to 4 weeks
scale, (57%) EC (1 pint in 50 gallons) after the first.
Spider mites Kelthane 2 teaspoons per gallon Use amounts of Ethion plus oil emulsion as for Scales.
(purple mites, (18'/%%) EC (1 pint in 50 gallons) Malathion will kill mites but not their eggs. If used for
Texas citrus mites, Ethion 2 teaspoons per gallon this purpose, a second application should be made 1 to 2
six-spotted mites) (25%) EC (1 pint in 50 gallons) weeks after the first.
Ethion plus Same as for
Oil emulsion Scales above
Rust mites Same materials as for Spider mites. Thorough coverage of leaves and fruit is essential.
(Chlorobenzilate is excellent
where available)
Aphids Malathion spray As directed on Inspect new growth carefully and treat before leaves

Neutral copper

Neutral copper

container label
As directed on
container label

As directed on
container label

Apply spray thoroughly to all surfaces just before new
growth starts in the spring and when 2A of petals have
Trees are usually more than 10 years of age before mel-
anose becomes a problem. Apply spray thoroughly to
young fruit, leaves, and tender twigs just after the flow-
ers shed.

The use of copper in the post-bloom spray and zineb or oil emulsion in the summer spray will aid
in the control of greasy spot (see pages 12 and 15).



Greasy spot

Many failures to control citrus pests, charged against the
insecticide, result from improper application and timing. A
gardner who has a substantial number of citrus trees is advised
to get a good sprayer. One to three-gallon compressed air mod-
els (Figure 26) can be used while trees are small. These models
are not expensive. Air pressure is pumped up by hand, 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 (Figure 27) 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 less
satisfactory for use on citrus trees, and in particular against
pests like scales and mites. 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.


Figure 26.-Two gallon compressed air sprayer.

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Figm 27 Sml pxersae


Care in Handling Pesticides.-Treat all pesticides as poisons
and handle according to the cautions on the manufacturers' prod-
uct labels. Always read the label carefully and completely be-
fore using the pesticide.
Pesticide Residues.-Citrus consumed by the producer should
be prepared by the generally accepted practices of washing, peel-
ing, etc. Dooryard fruit that is offered for sale must conform
with federal and/or state food and drug pesticide residue regu-
lations. 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 fol-
lows: Chlorobenzilate-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 days.
Oil Emulsion Sprays.-Do not apply oil emulsion sprays dur-
ing the winter months or to a tree which 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, as injury to, fruit and foliage may result.
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 mis-
take of spraying citrus trees and other plants with sprays formu-
lated 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
which should not be applied to plants because injury to the plants
usually results.

NOV 4 1976
OCT 2 0 '976

Four Keys to
Pesticide Safety


all cautions and warnings.

LABELED CONTAINERS, away from food
or feed. Keep them out of the reach of chil-
dren, pets, and irresponsible people.






Y'~LicF ~2B ~~

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