,- s 8-1434

arc AAay1983

LIBRARY

Devel Pmeht“

exas MrM University

of

Integrated Pest
Management

in

Texas Citrus

The Texas Agricultural Experiment Station, Neville P. Clarke, Director, The Texas A&M University System, College Station, Texas

 

CONTENTS

Summary . . . . . . . . . . A . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

History of Pest Problems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Factors AiTecting The Quality And Quantity of
Fresh And Process Fruit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Primary And Secondary Arthropod Pests And Their
Control

Major Changes in Pest Complexes Through Research . . . . . . . . . . . . . . . . . . . . .

Grower Pest Control Programs as Aflaected by
Integrated Pest Management Investigations . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Integrated Pest Management in Action . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

References Cited . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Page

ll
13
14

DEVELOPMENT OF INTEGRATED
‘PEST MANAGEMENT IN TEXAS CITRUS

H. A. Dean
Texas Agricultural Experiment Station
2415 East Highway 83
Weslaco, Texas 78596

J. Victor French
Texas A&| University Citrus Center
P.O. Box 2000
Weslaco, Texas 78596

Dale Meyerdirk
USDA, ARS, Boyden Entomological Laboratory
University of California Riverside 92521

The Texas Agricultural Experiment Station, Neville P. Clarke, Director, The Texas A&M University System, College Station, Texas

SUMMARY

A short history of citrus in Texas is provided along with
the changing citrus pest problems.

Data for over 25 years has been utilized for a better
understanding of major pest problems. Some former major
pests have become minor pests through introduction of eiTec-
tive parasites. Certain pesticide-related pest problems are
discussed. The discussion of pests, pesticides, and beneficials
are herein provided in order that the grower and pest control
operator may develop a more valid and effective pest man-
agement program at minimal cost. Such has been accom-
plished through effective Research and Extension Service
programs.

DEVELOPMENT OF INTEGRATED

INTRODUCTION

The earliest record of citrus plantings in Texas dates
back to 1849 when trees grown from seed were ex-
amined approximately 10 miles from Brazoria (50). Con-
sistent citrus production was not possible in the region
north of the Lower Rio Grande Valley (LRGV) because
of recurrent freezes. The earliest seedling trees in the
LRGV were planted in the 1880’s, about 20 miles north-
west of Edinburg (65). The first successful commercial
citrus plantings utilizing sour orange rootstock (75) were

Qmade in 1908 by Charles j. Volz, but it was not until

1920 that the LRGV was recognized as an important
citrus area. Market acceptance of Texas citrus has been
favorable, particularly the red mutations of grapefruit
that have been developed.

The Texas citrus area is comprised of 70,421 acres of
which approximately 63 percent is grapefruit-planted
and the balance mainly oranges. Hidalgo County has 83
percent of the total citrus acreage (61). The grapefruit
acreage is comprised of 84 percent ‘Ruby Red’ and 10
percent ‘Star Ruby’, with the remainder being pink and
white varieties. Future grapefruit plantings will prob-
ably be ‘Ray Ruby’ (49) and ‘Henderson’ Red (52), which
originated as bud mutations of ‘Ruby Red’. Their flesh
and peel color is redder and more attractive.

Early and mid-season varieties comprise 6O percent
of the orange acreage with the balance in late season
‘Valencia’ oranges. ‘Marrs’ is the earliest maturing vari-
ety and originated as a bud mutation from a ‘Navel’
orange tree (75). Some of the other orange varieties
include ‘Hamlin’ and ‘Pineapple’.

Fruit grown for the fresh market has generally
required more use of pesticides. Certain pests are con-
trolled by naturally occurring parasites and predators
while other pests are controlled with the use of selective
pesticides least destructive to natural enemies; thus,
pests are maintained below economic population levels.
If potential pests become major pests, additional person-
nel, equipment, and pesticides are required for their
control. Knowledge from research and experience are
provided herein to help the citrus grower to develop a
more effective and less expensive pest management

_ program.

HISTORY OF PEST PROBLEMS

California red scale, Aonidiella aurantii (Maskell),

' was the most destructive citrus pest in the LRCV until

1933 Citrus spray oil was the principal scalecide used
or its control. A hurricane in September 1933 blew most

f
l ‘f the fruit from the trees and pest control costs nearly

reached zero. Very little spraying of citrus was done
from then until the late 1950’s. Sulfur had continually
been applied (mainly in dust form) as the controlling

PEST MANAGEMENT IN TEXAS CITRUS

agent for citrus rust mite, Phyllocoptruta oleivora (Ash-
mead). However, the continued use of sulfur resulted in
increased populations of armored scales (6, 30).

As far back as 1929, parasites and predators had
reduced California red scale populations, in many in-
stances, to tolerable levels for fresh fruit shipment  In
1935, growers made a formal request for Texas Agricul-
tural Experiment Station at Weslaco (TAES W) to inves-
tigate the importance of biological agents for armored
scale control on Texas citrus. Initial studies in 1937
showed several important natural enemies of scale in-
sects.

The following list of citrus pests, in order of impor-
tance, was provided to Ebeling (1950) by S. W. Clark,
entomologist (TAES W from 1927 to 1937):

1. Citrus rust mite
2. Texas citrus mite, Eutetranychus banksi
(McGregor)

3. California red scale

4. Purple scale, Lepidosaphes beckii (Newman)

5. Glover scale, Lepidosaphes gloveri (Packard)

6. Mexican fruit fly, Anastrepha ludens (Loew)

7. Chaff scale, Parlatoria pergandii (Comstock)

8. Fire ant, Solenopsis geminata (F

9. Florida red scale, C hrysomphalus aonidum (L.)
10. Leaffooted bug, Leptoglossus phyllopus (L.)
11. Southern green stink bug, Nezara viridula 
12. Cotton aphid/melon aphid, Aphis gossypii

(Glover)

13. Brown soft scale, C occus hesperidum 

Zinebl sprays came into use in 1958 and provided
longer residual control of citrus rust mites. In many
instances, control lasted from 3 to 5 months in combina-
tion with oil (30). Other serious pest problems arose as
different pesticides came into use? Several of these
pesticide-related problems became evident in the
1960’s. Parathion drift from treated cotton produced a
major problem with brown soft scale, (21, 44, 45). Sevin
(carbaryl) was approved for control of brown soft scale,
but caused increased populations of chaff scale, Califor-
nia red scale, purple scale, Florida red scale, and Texas
citrus mites (22, 23). In 1970, following continued use of
organophosphorus pesticides, false spider mites,
Brevipalpus spp. , and citrus mealybug, Planococcus cit-
ri (Risso) became major problems affecting grapefruit.
(26, 21)

‘Trade names of pesticides will be used throughout (Diathane® Z-78,
zineb; Metacide, methyl parathion; and Nialate, ethion excepted) for
the convenience of readers (4). Common names of insects and
mites as approved by Entomological Society of America (68) will be
used.

zReference should be made to the current Texas Guide for Control-
ling Pests and Diseases on Citrus, Tex. Agric. Ext. Serv. Bull. 1336
for recommended pesticides and rates.

Pesticidal effects 0n secondary pests and their natu-
ral enemies were more important considerations, in
many cases, than the effects on the target pests. It was
evident that the effects of various pesticides were disrup-
tive to beneficial insect populations which resulted in
secondary pest outbreaks. Control of the secondary pest
is often more difficult and expensive than control of the
target pest. Changes in the order of importance of the
major pests since 1950 will be shown later in the text.

Integrated pest management investigations began
in the 1950’s and have continued to date.

FACTORS AFFECTING THE QUALITY AND
QUANTITY OF FRESH AND PROCESS FRUIT

Blemished fruit are more prevalent in some years
than others and must be sold for juice at reduced return
to the grower. A survey of seven packinghouses in
October 1980 showed that 26.6 percent (range: 14 to 5O
percent) of their total fruit had to be sold for processing.
Most rind blemishes do not affect internal juice quality,
but the U.S. Grade Standards (72, 73) must be met for
fresh fruit shipment. Based on packinghouse records for
three to seven seasons, the leading causes for fruit
blemishes with their respective average percentage and
range were: citrus rust mite, 25 (7-35); windscar, 25 (8-
35); undersize, 17 (9-25); melanose, Diaporthe citri
(Faw.), 10 (5-17); armored scales, 8 (0-17); mealybug, 5
(0-15); misshapened, 4 (O-15); brown soft scale, 1 (O-6);
and other, 5 (0-24).

Rust mite damages grapefruit more severely than it
does oranges (76) and it is the most serious citrus pest in
Texas. Rust mites can be effectively controlled by
acaricides; however, growers can do little to reduce
windscar, the second most widely occurring fruit blem-
ish. Undersized fruit occurs more often with certain
citrus varieties and is most prevalent during years of
higher fruit yields. Misshapened fruit (sheepnose, etc.)
were found in only two of the seven packinghouses
surveyed.

Maturity of Texas citrus is determined by minimal
soluble solids, soluble solids to acid ratios, and juice
content (5). For oranges, the minimal 8.5 percent solu-
ble solids and 1O to 1 soluble solids to acid ratios
(according to the state citrus color-add law) often allows
Marrs oranges to be shipped intrastate as early as Sep-
tember 15. At times, minimal juice is restrictive. Failure
of acid percentages to be low enough to meet minimal
soluble solids to acid ratios has been the principal re-
striction for intrastate movement of grapefruit. Minimal
fruit sizes of 2-1/4 and 3-9/16 inches in diameter for oranges
and grapefruit, respectively, has prevented movement
of small fruit to the fresh market (as authorized by
Federal Marketing Order 906 to the Texas Valley Citrus
Committee). Certain pesticides have been shown to
delay maturity, and retard fruit degreening (32).

Pesticidal residues and spray coverage can cause
problems when fruit is on the trees. Initial sprays are
usually applied at postbloom in late March or April when
some of the previous crop has not been harvested. Late
fall spray applications, principally for mite control, may

delay early fruit harvest. Growers are often confronted

with a decision as to which operation must come first. ~

PRIMARY AND SECONDARY ARTHROPOD
PESTS AND THEIR CONTROL

A list of Texas citrus pests and potential pests is shown
in Table 1 with the relative importance for only the top
four pests. j.

Primary Pests

The most important arthropod pests of Texas citrus
in 1980 were citrus rust mite, chaff scale, California red
scale, and Texas citrus mite. Control of citrus rust mite
must be considered in every pesticidal application to
citrus in the LRGV. Many growers apply an annual
(summer) scalecide treatment for control of chaff and
California red scales. Other growers wait until summer
before making a decision whether to spray or rely orr/r
natural enemies to maintain control of scale insects.
Texas citrus mites can cause significant damage to foliage
in dry years. Control of this mite is needed most when
dry weather conditions prevail following postbloom and
during the fall periods.

Citrus rust mite (Figure 1) — This mite has a high
reproductive potential and small populations may reach
damaging levels in a short period of time. A generation
may develop in 7 to 10 days during the warm season and
as many as 29 eggs may be laid by a single female (76).

Adult female mites are wedge-shaped and approxi-
mately l/zoo-inch in length. This small size makes detec-
tion difficult. A 1O to 14X hand lens is normally used for
determination of mite infestations in the grove. In early
season, undersides of leaves are checked (postbloom to
May); thereafter, fruit are examined. An inspection may
be required every 2 weeks during periods favorable for
mite population increases. The greatest numbers of
mites usually occur in the northeast quadrant of the tree
(9). Russeted fruit (Figure 2) are most frequently found
in the interior, top center, and skirt areas of the tree.
This suggests lack of pesticidal coverage in these areas.

High relative humidity (RH) has been a factor most
often related to increase of citrus rust mite populations.
In the LRGV, RH usually stays above 50 percent. Rust
mites increase very rapidly when RH exceeds 70 percent
(8, 74). Abnormally high rainfall conditions are also
followed by sharp increases in mites. Sharp reductions in
populations are found when RH drops below 1O percent
(8). In May 1972, an epiphytotic fungus, Hirsutella .
thompsonii (Fisher) developed following excessive rain-
fall during March and April (74) and live rust mites were
difficult to find in May and June of that year. This fungus
has provided the best potential control of rust mites of all
biological control agents in the area.

Acaraben® (chlorobenzilate) and Kelthane® (dicofol) a
have been the most widely used acaricides for control of
this mite. Residual control has been about the same for
the two materials but in certain tests (15), repeated
applications were required at shorter intervals witl
Acaraben than with Kelthane. Citrus rust mites were
controlled for 3 months or longer with a significant

/

reduction in mite-damaged fruit at harvest, with soil

,~applications of the systemic pesticide, Temik® (aldicarb)

12). Vendex® (fenbutatinoxide) can provide longer re-
sidual control than Kelthane with adequate coverage (36,
Dean unpublished). Vydate® (oxamyl) has provided 6 to
8 weeks suppression of this mite (34). Zineb can provide
long residual control, particularly with oil; however,
another acaricide must be added for initial quick kill
when high populations are present (30). Zineb and cop-
per treatments inhibit the development of the rust mite
fungus, H. thompsonii (53).

Ethion and Trithion® (carbophenothion) provide
good control, but residual control has been shorter with
Trithion (Dean and Tannahill, unpublished). Carzol S. P.
(formetanate hydrochloride) has provided longer residu-
al control than sulfur. Guthion® (azinphosmethyl) did

‘not provide sufficient rust mite control. The combination

of Acaraben or Kelthane with Supracide (methidathion),
as well as copper, has been associated with some popula-
tion increase of this mite (15, 35).

Chafi scale (Figure 3) Chaif scale has been the
most widely distributed and abundant armored scale in
the commercal citrus area of Texas during the past 2O
years. All life stages have been found during every
month of the year, indicating reproduction occurs
throughout the year. The insect attacks all parts of the
tree aboveground, and may be particularly abundant
under the calyx (button) of the fruit and in pits of the rind
(24).

Aphytis hispanicus (Mercet) is the most common
parasite of this scale, although Prospaltella fasciata
Malenotti has been found quite numerous at times (11).
Aphytis lingnanensis Compere and Aphytis comperei
DeBach and Rosen have also been reared from this

TABLE 1. POTENTIAL ARTHHOPOD PESTS OF CITRUS IN THE LOWER RIO GRANDE VALLEY, TEXAS

Common Name‘

Class Family Species
Arachnida:

Eriophyoidae Phy/locoptruta o/eivora (Ashmead)2

Tetranychidae Eutetranychus banksi (McGregor)5
Panonychus citri (McGregor)

Tenuipalpidae Brevipalpus ca/ifornicus (Banks)
B. phoenicis (Geijskes)

lnsecta:

Diaspididae Par/atoria pergandii (Comstock)3
Aonidiella aurantii (Maskell)“
Chrysomphalus aonidum (L.)
Lepidosaphes, beckii (Newman)
L. gloverii (Packard)

Coccidae Coccus hesperidum L.
Ceroplastes cirripediformis (Comstock)
lcerya purchasi (Maskell)
Saissetia miranda (Cockerrell & Parrott)

Aleyrodidae Dialeurodes citri (Ashmead)
D. citrifo/ii (Morgan)
Aleurocanthus woglumi (Ashby)
Aleurothrixus floccosus (Maskell)
Paraleyrodes citri (Bondar)

Pseudococcidae P/anococcus citri (Risso)
Pseudococcus longispinus (Targioni-Tozzetti)
Pseudococcus calceolaria (Maskell)

Pentatomidae Loxa florida (Van Duzee)

Aphididae Aphis gossypii (Glover)
A. spiraecola (Patch)

Papilionidae Papilio cresphontes (Cramer)

Curculionidae

Compsus auricephalus (Say)
Epicaerus mexicanus (Sharp)

Flatidae Metca/fa pruinosa (Say)
Coreidae Leptog/ossus phyllopus (L.)
’A Formicidae Atta texana (Buckley)
Solenopsis geminata (F.)
Crematogaster laevinscula clara Mayr.
fa C. arizonensis (Wheeler)
Tephritidae Anastrepha ludens (Loew)

citrus rust mite

Texas citrus mite
citrus red mite

(false spider mite)

red and black flat mite

chaff scale
California red scale
Florida red scale
purple scale
Glover scale

brown soft scale
barnacle scale
cottonycushion scale
Mexican black scale

citrus whitefly
cloudywinged whitefly
citrus blackfly

woolly whitefly

citrus mealybug
longtailed mealybug
citrophilus mealybug

(stinkbug)

cotton or melon aphid
spirea aphid

orangedog

(snout beetle)
(snout beetle)

(flatid planthopper)
leaffooted bug

Texas leafcutting ant
fire ant

Mexican fruit fly

‘Common names approved by Entomological Society of America, names in parenthesis only for information.

Zthrough 5: Order of economic importance of primary pests.

insect (Dean unpublished). Numbers of parasites are
usually higher during September and October, although
high numbers have been found in rainy spring months
following warm winters (Dean unpublished). Drier
weather conditions are usually more favorable for in-
crease of chaff scales than their parasites.

California red scale (Figure 4) —- This scale has
three and possibly four generations each year (7). Great-
er numbers are usually found in those years when dry
weather conditions prevail during the spring and sum-
mer when parasites are less abundant. Growers often
mistake chaff scale for California red scale. In Texas,
damage to twigs and young newly planted trees (32) can
be greater from California red scale than from chaff
scale.

A. lingnanensis has been the most effective parasite
in Texas citrus, and has given economic and sustained
control in many instances (29). Efforts to establish Aphy-
tis melinus DeBach or Aphytis africanus Quednau in
Texas have not been successful.

Texas citrus mite (Figure 5) —— This mite was de-
scribed in 1914 in collections from castor bean and velvet
bean at Orlando, Florida (54). In the LRGV, the mite
has been found predominantly on citrus. Most of the
year numbers were greater in south quadrants of grape-
fruit trees (9). Peak populations usually occurred during
May through September, although peaks have occurred
in mid-March from large winter populations when warm
temperatures prevailed during February and March (8,
16). Greater numbers were found on leaves in the tops of
trees than in skirt or inside canopy areas (l4) and greater
populations also occurred on Marrs than on Hamlin,
Pineapple, or Valencia orange leaves (16). Damage (Fig-
ure 6) has been principally to leaves, but it will feed on
fruit. Leaf drop has been associated with high mite
populations, particularly following dry weather
conditions.

Longest residual mite control has been with Vendex
and Kelthane (34, Dean unpublished). Effective control
has been difficult to attain when populations are increas-
ing rapidly, such as during April and May. Ethion,
Trithion, Carzol S.P., and oil have not been as effective
as the aforementioned acaricides. Some reduction in
mite numbers have been noted following use of Acara-
ben or sulfur. Increased mite populations have followed
the use of Zineb (30) or copper (15). This may be caused
by the destruction of a mite fungus, Entomophthora
floridanus Weiser and Muma. The fungus was first
found in the LRGV in 1969 (51). Increases in mite
populations have also been observed following use of
Supracide or Sevin, even though effective acaricides
were added (35, 15, 24).

Secondary Pests

Secondary pests are potential or minor pests nor-
mally held below the economic injury level by their
natural enemies or weather conditions. Outbreaks of
secondary pests result when their natural enemies are
killed by pesticides applied for target pest control; by
pesticidal drift from adjacent crop land; by improper
timing, mixtures, or selection of pesticides; and by‘ in-

4

adequate coverage. Some secondary pest outbreaks re-
sult from indirect causes. Methyl parathion stimulated‘

reproduction of brown soft scale (46). Road dust froi. 

frequently traveled roads can settle on adjacent citrus
trees and act as a drying agent thus causing eradication of
natural enemies. A discussion of secondary pests, not
necessarily in the order of importance, follows.

Citrus mealybug (Figure 7) — Planococcus citri
(Risso) has three to four generationsfper year in South
Texas and possesses a high reproductive potential (43).
Under optimum conditions the mealybug can complete
development in 30 days. Individuals of the first genera-
tion are usually found under the calyx of the young fruit
in the spring. Preference for grapefruit was found in
Texas over other plant parts and other varieties (55). The
winged male is the only motile stage which does not
feed. Following natural enemy destruction by pesticidal
misuse, the populations will increase to high levels by;
the second or third generation. Sooty mold, Capnodium
citri Berk. 6t Desm. , develops in the excreted honeydew
of this mealybug. White filamentous wax secretions pro-
duced by the egg-laying females and their body wax can
cause the fruit to appear as white snowballs. Outbreaks
in 1969 and 1970 in South Texas were associated with
continued use of broad spectrum organophosphate pes-
ticides (22). These pesticides were detrimental to benefi-
cial insects (23, 63, 57). Sex pheromone traps were found
to be effective for survey and indexing the population
density of the citrus mealybug (43, 33). Oil, which
controls only the youngest stages of the mealybug, was
used successfully in an integrated pest management
program because of minimal disruptive effects to the
natural enemy complex (56). Insect growth regulators
also appeared promising for citrus mealybug control (40).
Parasites included Pauridia peregrina Timberlake, Lep-
tomastix dactylopii Howard, and Anagyrus sp. near
sawadai Ishii (59, 22). Predators were a brown lacewing,
green lacewing species, and a predaceous beetle (22,
63). Vine control was important in controlling mealybugs
in infested grapefruit groves (39).

Whiteflies (Aleyrodidae) — The citrus whitefly,
Dialeurodes citri (Ashmead), and the cloudywinged
whitefly, Dialeurodes citrifolii (Morgan) (Figure 8), are
the only whiteflies of potential economic importance of
the five species on citrus in Texas (60). These two species
can become pest problems in early and late spring. They
excrete copious amounts of honeydew. Although quite
similar, the species can be differentiated by their eggs on
the lower leaf surface: citrus whitefly eggs remain yellow
during maturation and have a smooth surface while
cloudywinged whitefly eggs change color from yellow to
black and have a net-like surface. A darkened area at the
tip of the forewing occurs only in cloudywinged whitefly q
adults. No parasites were found attacking either speciea;
in South Texas. A red fungus, Aschersonia aleyrodes
Webber, was found infecting citrus whitefly while some
occasional predation was observed.

(continued on page 9)

\al

Figure 1.
Citrus rust mite.
Ca. 14X.

Figure 2.
Russeted grapefrui
by citrus rust mite.

Figure 3.
Chaff scale.
Ca 9X.

Figure 4.
California red scale.
Ca. 9X.

5.
ci

Figure
Texas

trus mites.

Ca. 13X.

6.
m
u

hi8

F

Texas
citrus leaves.

citrus mite damage to

Figure 7

Citrus mealybug.
Ca. 4X.

Figures 8 a & b.

b. Citus itefly n yph. a 3x.

Figure 9.
Purple scale and its

controlling parasite.
Ca. 8X.

Figure 10.

Brown soft scale.
Ca. 5X.

4!.
1
m
U
hlu
F

Florida red scale
on orange.

e

S

0

Wm
247W
1me
3w
wmw
lwan
FS0

The citrus blackfly, Aleurocanthus woglumi Ashby,

rx became well established in the LRGV despite eradica-

tion attempts in 1971. Yellow traps became an effective
tool for surveying and indexing the population density of
this species (47). Adults have a red abdomen and grey-
blue wings. Eggs are laid in a typical spiral pattern 0n
the lower leaf surface. Nymphs and pupae are black with
conspicuous spines, and pupae have a white wax band
around their margin. Complete biological control was
evident after the introduction of two parasites: Amitus
hesperidum Silvestri (Platygasteridae) and Prospaltella
opulenta Silvestri (Encyrtidae) (67).

The woolly whitefly species, Aleurothrixus floc-
cosus (Maskell) and Paraleyrodes citri Bondar, are both
under complete biological control in the LRGV (60). The
former is attacked by three species of parasites: Eret-
mocerus sp. , Amitus sp., and a Prospaltella sp.; P. citri is
attacked by a single Prospaltella sp. A coccinellid preda-
tor, Delphastus pusillus (Le Conte)’attacks both whitefly
species while the coccinellid, Nephaspis amnicola Win-
go, has been observed feeding only on P. citri. The
woolly whitefly lays eggs in a typical circle configuration
and nymphs and pupae are covered with a secretion of
white wool-like wax filaments. P. citri lay eggs singly and
nymphs and pupae are transparent with long cascading
wax rods.

Brown so t scale —— Coccus hesperidum L. (Figure
10) is a flat, ovate soft scale yellowish brown in color. Its
life cycle is completed in approximately 6O days. Copi-
ous amounts of honeydew often result in heavy encrusta-
tions of black sooty mold. The insect became a major
pest in 1959 (21) when natural enemies were killed by
parathion drift from adjacent cotton fields (45). Methyl
parathion caused increased fecundity of this insect (46).
In the absence of methyl parathion treatments in cotton,
the brown soft scale is no longer a major pest problem in
Texas. It is believed to be under complete biological
control by two dominant parasites: Coccophagus lycim-
nia (Walker) and M icroterys flavus (Howard) (44).

Cottonycushion scale — I cerya purchasi Maskell is
a soft scale which can secrete copious amounts of honey-
dew. The female is characterized by the grooved, white
waxy egg sac which is 2 to 2-1/2 times the length of her
body (32). There are three generations per year with a
life cycle ranging from 96 to 144 days (62). The vedalia
beetle, Rodolia cardinalis (Mulsant), provides complete
biological control in the LRGV. Sporadic infestations
may result from misuse of pesticides which kill the
vedalia beetle.

Florida red scale —— This scale insect (Figure 11, on
fruit) attacks the fruit, leaves, and occasionally the green
twigs. Today, it is only a minor pest due to the in-
troduced parasite, Aphytis holoxanthus DeBach, in 1959
(2, 17). Two other parasites, Pseudhomalopoda prima
Girault and Prospaltella aurantii (Howard) are present
only in small numbers in the presence of A. holoxanthus.
Pesticide-induced outbreaks occur following use of Sup-
racide, Sevin, and sulfur (17).

Purple scale — This scale insect (Figure 9) was the

fourth most harmful pest of Texas citrus in 1950 (32).

Very little parasitization of this scale insect was found

before the introduction of Aphytis lepidosaphes Com-
pere in July 1952 (10). Sulfur was used primarily in dust
form for control of citrus rust mite at that time, and even
though A. lepidosaphes was found quite commonly (10),
purple scale population densities were not sharply re-
duced until other pesticides less toxic to the beneficial
insects were used beginning in 1960. Complete biologi-
cal control was found by 1975 (13).

Glover scale — This scale insect has been an eco-
nomic pest problem only in a few isolated groves during
the past 27 years. Prospaltella elongata Dozier has been
the principal parasite collected most often from this scale
insect, while Aphytis sp., has been collected on numer-
ous occasions. When found, Glover scale is usually
associated with purple scale, with which it is confused.
The adult Glover scale covering is narrow and its body
under the cover varies in coloration from white to pur-
ple. The purple scale body is a chalky white color and
the scale is “comma-shaped.”

Citrus red mite — Panonychus citri (McGregor) was
first found in commercial grapefruit and orange groves in
Texas near Combes in january 1980 (37). The mite has
been found in groves south and eastward toward the
Gulf since that time (38). Heavy infestations were found
on Ruby Red and Star Ruby grapefruit; ‘Orlando’
tangelo; and on ‘joppa’, Navel, and Valencia oranges.

Somewhat larger than the Texas citrus mite, citrus
red mite is recognized by the velvet red body which has
prominent tubercles with long, reddish bristles. Eggs
are round and bright red, and have a central stalk with
threads radiating from the top to the leaf surface like a
maypole. Eggs are generally laid alongside the midrib on
the upper leaf surface.

F oliar applications of Vendex or oil as well as soil-
applied Temik have produced good control (36).

False spider mites — Brevipalpus phoenicis (Geijs-
kes) and B. californicus (Banks) become potential prob-
lems when organophosphorus pesticides are used for
control of other pests. B. phoenicis is the most common
of the two species. These mites are associated with a
“leprosis-like” spotting of fruit, particularly on grape-
fruit. Increases in" mite populations were observed on
inside fruit and leaves in June followed by high popula-
tions in August and September (26). In general, these
mites have not reached pest status where Kelthane,
Acaraben, sulfur, or oil have been used.

Mexican fruit fly — This fruit fly is indigenous to
northeastern Mexico and infests numerous citrus, de-
ciduous, and wild host species. Northward migration of
this fruit fly is a potential pest for citrus in the LRGV and
other citrus as well as deciduous fruit areas from the
migration spread. The first record of this fly in the LRGV
was in 1927 (3). Since that date, a rigorous survey and
detection program was established by USDA. Fly traps
showed this fruit fly as early as October, with peak
populations in the March through May period. Fly
larvae feed and develop within the fruit. Infested fruit
can possibly be shipped since there may be no evidence
of rind injury. Quarantines and regulatory fumigation
with EDB (ethylene dibromide) have been established
to insure against this possibility.

Lflatid planthopper —— Metcalfa pruinosa (Say)
usually hatches in mid-March with adults appearing in
late April 0r May. Only one generation per year occurs
in South Texas, but adults may be found as late as
September. Honeydew is abundantly secreted during
very dry spring months by the nymphs which have a
cottony appearance and are sometimes mistaken for
citrus mealybug. Grapefruit trees are preferred over
oranges. Pesticidal control is usually not required. A
dryinid parasite, Psilodryinus typhlocybae (Ashmead),
has caused heavy parasitization in some years (20).

Barnacle scale —— C eroplastes cirripediformis Com-
stock is an oddity on Texas citrus. A ‘Meyer’ lemon tree,
infested with a mild strain of tristeza virus, was caged
with fine-mesh plastic screen at TAES W in 1955. Barna-
cle scale increased rapidly in numbers, but almost disap-
peared a short time after the cage was removed and
numerous natural enemies were present.

l Early in 1975, infestations of this scale insect were
found in the eastern and western sections of the LRGV
(41). A complex of parasites were important in biological
control of barnacle scale as it was difficult to find this
scale insect in 1977 (27). Thus, barnacle scale is con-
trolled by its natural enemies unless the latter are killed
by pesticides or hyperparasites become numerous and
prevent parasites from maintaining control.

Aphids — Aphid species most frequently found on
the LRGV citrus are the spirea aphid, Aphis citricola
Van der Goot, and the cotton or melon aphid, Aphis
gossypii Glover. Aphids can cause severe leaf curl of new
growth. Pesticidal control is usually not necessary be-
cause of effective control by natural enemies. According
to identification records, Aphidius testaceipes (Cresson)
has been the most common parasite. Both aphids are
inefficient vectors of tristeza virus (28). This disease has
never been a problem in the LRGV even though more
than 95 percent of the citrus is planted on susceptible
sour orange rootstock.

Snout beetles — Compsus auricephalus Say is the
most common in the area. The adult weevil is approxi-
mately 11 mm long and greenish-gray in color, has a
broad snout, and feeds on foliage, while the larvae are
root feeders. The adult of another less common species,
Epicaerus mexicanus Sharp, is blackish-brown in color
and about the same length as the C. auricephalus. Most
species produce only one generation a year.

Mg —— Ants may cause direct injury to the trees or
may interfere with natural control of pests by their
parasites and predators. The most common ant is the fire
ant, Solenopsis geminata (F.), which may feed on the
bark, often girdling and causing death of young citrus
trees (66). Fire ants will nurse honeydew secreting
insects such as aphids, mealybugs, and brown soft scale.
They can also be a nuisance to pickers and other grove
workers.

Acrobat ants will nest in foliage of the tree, in holes
of wood boring insects, or at the base of the trees. They
also feed on honeydew and interfere with biological
control agents. The two particular species identified are
C rematogaster laevinscula clara Mayr. and C. arizonen-
sis Wheeler. The former is reddish-orange, while the

10

latter is entirely black.
The Texas leafcutting ant, Atta texana (Buckley),
can cause citrus defoliation (64).

MAJOR CHANGES IN PEST
COMPLEXES THROUGH RESEARCH

A. Information on the selective effects of pesticides
against target species and their naturalcontrol agents is
of immense value to the grower and pest control
operator. Such information can help them avoid the
creation of new pest problems as well as increase the
residual effectiveness of pesticides against the target
pests. Extension Service personnel began to use this
information as soon as it was made available. The citrus
agroecosystem of pests and their natural enemy complex
can be better understood by citrus growers when this
information is discussed with them by research and
extension personnel.

B. Purple scale was reduced from the fourth most
harmful pest of Texas citrus in 1950 to that of incidental
occurrence status by the early 1970’s. The ability of the
introduced parasite, Aphytis lepidosaphes Compere, to
re-enter after certain adverse pesticidal applications and
bring about control is very unusual (10). Control of
purple scale by this parasite is more effective than the
pesticidal control formerly used. This is a classic example
of biological control (13).

C. Research with oils has produced specifications
which provide guidelines for most-effective pesticidal
oils with the least adverse tree effects (19). Target
species cannot develop resistance to oil and it does not
produce the disruptive effect on the natural enemies as
do many of the organophosphorus pesticides (58). Oil is
the most selective scalecide available, but many years of
research were necessary to gather data on its proper use
and efficacy against specific pests.

D. Florida red scale was reduced from the ninth
most destructive pest of Texas citrus in 1950 to inciden-
tal pest status by 1972. An introduced parasite (Aphytis
holoxanthus DeBach) in 1959 reduced the economic
importance of this pest when adverse pesticides were
not used (17). By killing this effective parasite with the
use of Supracide and/or Sevin, Florida red scale will
become a problem. Reduction of the pest status of this
insect was a very important contribution to the Texas
citrus industry.

E. Brown soft scale was determined to be a
parathion-related problem on Texas citrus (46). Nine
natural parasites were identified and others were im-
ported to provide more effective control under a wide
variety of conditions. Fruit blemishes attributed to
brown soft scales were reduced to less than 1 percent at
the packinghouses.

F. Citrus mealybug was determined to be a ~.

pesticide-related problem and caused by the particular
pesticides applied to the trees (22). Results showed the
problem could be avoided, or limited, by selective use of
certain pesticides (40). Biological control agents (both
native and introduced) have provided effective control
(59).

G. The early introduction of parasites for control of

vb

citrus blackfly prevented this insect from becoming a prebloom treatment was justified (l5). Every grower

p possible major pest to Texas citrus. After establishment should consider citrus rust mite control at this time.
in the early 1970’s and eradication attempts were unsuc- The greatest increase of Texas citrus mites during
cessful, two effective parasites were introduced from the year generally occurs during the April to June
Mexico and distributed throughout the infested areas. period, and because of the importance and potential
Complete biological control was the result (67). damage of this pest, control at this time is considered

necessary (16). Generally, populations of Texas citrus
mites are lowest in February, but usually increase rapid-
ly with the warm weather. These mites may also increase
rapidly during favorable fall weather conditions.

GROWER PEST CONTROL PROGRAMS
AS AFFECTED BY INTEGRATED PEST
MANAGEMENT INVESTIGATIONS

Selective effects of various pesticides against various Armored scales usually increase after the postbloom
pests and certain natural enemies are provided in Table 2. period with warming weather. Parasites are often at
The first pesticidal application of the year is general- their lowest level of the year during February and
ly made at postbloom (when three-fourths of the petals March, particularly following cold winters (11, 17). Con-
havefallen) or soon thereafter. At that time, citrus rust sideration of armored scale control at postbloom is ques-
mite can move onto young fruit and cause considerable tionable. Coverage of all parts of the tree is necessary if
damage. An unusually heavy increase of rust mites can satisfactory scale control is to result. Since complete air
T occur early in the year when the last treatment for displacement is essential, the necessary volume of liquid
control was made during the prior August to September to accomplish control is greater than many growers
period and weather thereafter was favorable for rust realize. Complete coverage cannot be accomplished
mites to increase during the fall and winter (15). Damag- with 25 to 125 gallons per acre in this area.
ing levels of rust mites were found in Ianuary and All commercial varieties of citrus may be attacked

TABLE 2. EFFECTS OF VARIOUS PESTICIDES AGAINST CERTAIN TEXAS CITRUS PESTS AND NATURAL ENEMIES

i? e2 ® %  g gig e g
CITRUS PESTS: g m i‘, 9, = 2 . 3 g ,9 c i; g ,1.’ g, 2
a i5 ‘é i» -9 s é t: a 5 -; a. E e s 8
2 :2 s é 5 E a a s a a a s .2 8- .2 >>
Citrus rust mite 4 4 4 3-4 4 3-4 2-3 3 1 a 1 — a 4 3-4 2-3 3
Texas citrus mite 1-2 4 4 0 3-4 3-4 1-2 3-4 3-4 d 2-3 d a 3 3 — 1
Citrus red mite 1 4 4 — — — — 2-3 3-4 c-d — — — 3 3 — 1
False spider mites 4 4 — 0 c c 3 — 3 — — — — — — -
Chafl scale N N N N a b b-c c 4 4 4 d a 1-2 — — —
California red scale N N N N N a b-c c 3-4 3-4 3-4 d a 1-2 — — —
Purple scale N N N N N a c — 4 4 3-4 d a — — — —
Florida red scale N N N N — — c c 4 c-d — d a 1-2 — — —
Brown soft scale N N — — 1 -2 3 — a 3 4 4 4 — 3 — 3 —
Citrus mealybug N N — N a-b a-b — — 1-2 3-4 2 — — 3 — 1-2 3
Whiteflies N N N — — — — — 2-3 3-4 3 — — 3-4 — 2-3
PARASITES:
Ext. chaff scale N N N N b c b-d c-d a c-d c-d d a — — — -
lnt. chaff scale N N N N b c b-d c-d a c-d c-d b a — — — —
Ext. CA red scale N N N N c c b-c d a b-c d d a — — — —
Ext. purple scale N N N N c c b-c — a — d d a — — — —
Ext. FL red scale _ N N — — c c-d c-d c-d a c-d d d a — — — —
A lnt. brown soft scale — — -— — — — d — a — d d — — — — —
PREDATORS:
“Lady beetles N N N — a a-b — — a c-d c-d d — — — -- —
Brown lacewing N 2 N -— a b — — a-b d d d — — — — —

Numbers: 0 to 4 = degree of kill by pesticide. Letters: a lowest to d highest = degree of increase of insects or mites, or degree of reduction of parasites found. N =
no effect noted. (—) = no information. (Ext) and (lnt.) = external and internal parasites.

11

by melanose (Figure 12), but grapefruit seems more
susceptible (1). The disease is more prevalent in the area
from Mercedes eastward. Infection of fruit is more pro-
nounced when fruit is less than three-fourths of an inch
in diameter and in groves when wet weather prevails
during this period or in groves where greater infection
has occurred. Late melanose infection can occur in the
June to ]uly period when proper weather and other
conditions prevail. Copper is the principal ingredient of
the fungicides used in melanose control. Coverage of
twigs, leaves, and fruit is necessary to accomplish effec-
tive control. However, residual control of citrus rust
mite and Texas citrus mite is reduced when Acaraben or
Kelthane is mixed with copper (15). The most important
biological control agent of citrus rust mite in our area is
the fungus, Hirsutella thompsonii Fisher, which copper
kills (53). Copper also kills an important fungus of the
Texas citrus mite, Entomophthora floridana Weiser and
Muma. Indiscriminate use of copper is to be dis-
couraged.

The citrus nematode, Tylenchulus semipenetrans
Cobb, is a serious pest of citrus with approximately 90
percent of the orchards infested in the LRGV (48).
Nematodes are wormlike, invisible to the unaided eye,
and attack the root system causing general tree decline.
A nematicide for control is generally applied prebloom
or just after bloom. DBCP (dibromochloropropane), a

highly effective nematicide applied in the irrigation wa-

ter, is no longer approved for use. An alternative system-
ic nematicide-acaricide receiving increased grower use is
Temik® (aldicarb). Granular Temik is chiseled I to 2
inches into the soil at the drip line of the tree and
activated by irrigation water. Temik applications in a
‘Marrs’ Early Orange orchard at 33 and 67 lb/acre signifi-
cantly reduced nematode populations in each of the
three seasons of testing and significantly increased yield
in 1 of 3 years (71). Temik activity against whiteflies,
brown soft scale, Texas citrus mites, and mealybugs has
been found in current research (French unpublished).

Vydate® (oxamyl) is a nematicide-acaricide recently
registered for use on Texas citrus. Applied as a foliar
spray, Vydate translocates systemically downward to the
roots. Nematode control and fruit yield improvement
has been less consistent with this material than with
DBCP or Temik (69, 70, 71).

Pesticide selection at postbloom can directly affect
pest problems throughout the season. Many growers
that have used concoctions of various pesticides to con-
trol mites and avoid problems with other potential pests
have learned this is not a valid approach to minimize
pest problems. Postbloom applications are primarily for
control of citrus rust mite and Texas citrus mite. Howev-
er, control of scale insects is sometimes necessary at
postbloom, and careful selection of scalecides is neces-
sary to avoid reduction or knockout of parasite popula-
tions that could result in a sharper increase of armored
scales, or other potential pests by early summer. Delay-
ing postbloom application 1 to 3 weeks, if practical, can
provide additional time for scale parasites to increase.

The decision for a pesticidal application following
postbloom should be determined by grove surveys for

12

pest populations. Generally, increase of citrus rust mite

and armored scale populations are reasons for a second -

pesticidal application. Scalecide applications, when
necessary, are usually applied during the June through
September period. According to a study by Clark and
Friend (1932) and later investigations by the authors, a
full coverage scalecide application in early to mid-
summer will usually provide control for the balance of
the season. Only three scalecides have been successfully
used in this area: oil, Guthion, and Supracide. Each of
these scalecides have their limitations.

In Texas, properly applied oil has been a very useful
and selective pesticide for armored scale and Texas
citrus mite control. Scales are killed with oil by suffoca-
tion (31), and this phenomenon does not offer a ready
mechanism for the development of resistance. The use of
oil has been preferred over certain organophosphorus

pesticides for scale control because of other pest prob- .9

lems that have developed following applications of the
latter (26, 23, 17). Oil undoubtedly kills some adult
parasites. Immature parasites have protection under the
scale coverings, and residual oil having soaked into the
plant tissues, does not kill the emerging parasites as
found with residues of organophosphorus pesticides.
Chaff scale parasites were usually found with a smaller
scale population at an earlier date after oil application
than after certain organophosphorus pesticides. This was
an advantage of oil (25).

Specifications for citrus oils (19) are still valid today.
Oils developed for use on citrus in the 1960’s produce
only minimal tree reaction when properly used. Soil
moisture should be at a maximum when applications are
made. Lack of coverage reduces pest control efficiency
with any scalecide when volumes of less than 500
gallons/acre are used. Certain other restrictions also
must be observed with oil applications: use after Sep-
tember 15 deters the development of soluble solids of
grapefruit and the meeting of minimum maturity stan-
dards for early fruit shipment; increased cold susceptibil-
ity of citrus when applied late; and delay in coloring of
fruit for 3O days in the packing sheds for fresh fruit
shipments. Oil is not suggested when RH is below 3O
percent, which occurs infrequently.

The organophosphorus pesticides Guthion and Sup-
racide kill most beneficial insects and considerable time
is required for biological control agents to re-establish
after their use. A problem with Florida red scale can be
expected after the use of Supracide even though some
control results (16, 15). Numerous studies have shown
that the Texas citrus mite can increase in importance in a
relatively short time period after application of these
pesticides (12, 15). False spider mites become an eco-
nomic pest when organophosphorus pesticides are used
and no Kelthane, Acaraben, sulfur, or oil are applied .
during the May to September period (26). Moreover,
the use of organophosphorus pesticides requires much
greater personnel protection for the applicator safety. In
addition, total tree coverage is absolutely necessary if
satisfactory control is to result.

Greasy spot, Mycosphaerella horii (Harii), is a fun-
gus disease which causes a “greasy-like" spotting of the

undersides of leaves, particularly with grapefruit. Where
~control is necessary, oil or copper applied during the
zummer usually provides adequate control.

The last pesticidal application of the year is usually
made during the fall. This application is to provide citrus
rust mite control until the following postbloom season.
Texas citrus mites can increase in populations in con-
junction with dry, hot, and windy weather in October
and November. Heavy infestation can result in consider-
able loss of leaves. Pesticidal control of armored scale
insects during this period is considered too late to be
effective. Armored scale parasites are numerous at this
time, and if their numbers are reduced or eliminated,
armored scales can increase thereafter without biological
control assistance.

The number of pesticidal applications each year

Kvaries from grove to grove depending on location,
weather conditions, and variations in pest to natural
enemy ratios. One grove may require only two pesticidal
applications a year, while another may need five or
more. Some growers who have been ill-advised may
apply excessive sprays during the year. The foregoing
discussion is certainly n_ot intended to endorse a calendar
spray schedule and this is not recommended. Informa-
tion is provided to develop a knowledgeable approach to
the grower pest management program. The reduction of
one or two applications per year may require extra effort.

Pesticidal decisions based on careful monitoring of
groves for pests and their biological control agents will
result in less expensive pesticide bills. Other benefits
include utilization of natural enemies, fewer major pest
problems, and a less complicated pest control program.

INTEGRATED PEST MANAGEMENT IN ACTION

The Texas Agricultural Extension Service has uti-
lized research data on various citrus pests and their
natural control agents down through the years. Greater
emphasis was considered in the control of target pests
with pesticides in earlier work. A greater variety of
pesticides became available for use on citrus in the
19603. Additional problems with minor pests developed
after continued use of many of these pesticides.

The effects of certain pesticides against various
pests and their natural enemies were summarized in
1977 (23). The Extension Service began use of these pest
management considerations immediately after release of
the information. A better understanding of the citrus
ecosystem and potential factors for possible changes or
upsets were provided. Such information was reproduced
for distribution as a guide in development of more valid
and economical pest management programs for the
growers as part of the Texas Guide for Controlling Pests
and Diseases on Citrus, 1979. A revised edition of this
information is provided in Table 2.

13

REFERENCES CITED

1. Amador, I. M. 1978. Texas citrus: diseases. In producing and
marketing Texas citrus. Tex. Agric. Ext. Serv. Bull. 1178.

2.Bailey, I. C., and H. A. Dean. 1962. Zineb versus maneb for citrus
rust mite control. I. Rio Grande Valley Hortic. Soc. 16: 22-5.

3. Baker, A. C. 1939. The basis for treatment of products where
fruitilies are involved as a condition for entry into the United
States. U.S. Dept. Agric. Cir. 551. 8 pp.

4. Billings, S. C. 1974. Approved list of approved common names of
insecticides and other pesticides. Pesticide Handbook-Entoma,
1974.

5. Brown, R. 1977-78. Texas produce industry guide. Tex. Dept.
Agric. citrus maturity law. Art. P.C. 719a.

6. Clark, S. W. 1928-37. Annual report. Tex. Agric. Exp. Stn. No.
15, Weslaco (Unpublished).

7. Clark, S. W., and W. H. Friend. 1932. California red scale and its
control in the Lower Rio Grande Valley of Texas. Tex. Agric. Exp.
Stn. Bull. 455. 35 pp.

8. Dean, H. A. 1959a. Seasonal distribution of mites on Texas grape-
fruit. I. Econ. Entomol. 52: 228-32.

9. Dean, H. A. 1959b. Quadrant distribution of mites on leaves of
Texas grapefruit. I. Econ. Entomol. 52: 725-7.

10. Dean, H. A. 1961. Aphytis lepidosaphes (Hymenoptera: Chal-
cidoidea), an introduced parasite of purple scale. Ann. Entomol.
Soc. Amer. 54: 918-20.

11. Dean, H. A. 1965. An Aphytis complex (Hymenoptera:
Eulophidae) of chaff scale. Ann. Entomol. Soc. Amer. 58: 142-5.

12. Dean, H. A. 1969. Control of citrus mites with certain pesticides
during 1966-68. I. Rio Grande Valley Hortic. Soc. 23: 51-6.

13. Dean, H. A. 1975. Complete biological control of Lepidosaphes
beckii on Texas citrus with Aphytis lepidosaphes. Environ. En-
tomol. 4: 110-4.’

14. Dean, H. A. 1976. Prevalence of Texas citrus mites in certain areas
of orange trees. I. Rio Grande Valley Hortic. Soc. 30: 27-30.

15. Dean, H. A. 1979. Citrus rust mite control affected by certain
pesticides. I. Rio Grande Valley Hortic. Soc. 33: 55-7.

16. Dean, H. A. 1980. Population differences of Texas citrus mites on
leaves of four orange varieties in Texas. I. Econ. Entomol. 73:
813-6.

17. Dean, H. A. 1982. Reduced pest status of the Florida red scale on
Texas citrus associated with Aphytis holoxanthus. A. Econ. En-
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18. Dean, H. A., and I. C. Bailey. 1960. Introduction of beneficial
insects for the control of citrus scale insects and mites. I. Rio
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19. Dean, H. A., and I. C. Bailey. 1961. Properties of spray oils for
grapefruit in the Rio Grande Valley of Texas for 1961. I. Rio
Grande Valley Hortic. Soc. 15: 10-11.

20. Dean, H. A., and I. C. Bailey. 1961. Aflatid planthopper. Metcal-
fa pruinosa. I. Econ. Entomol. 54: 1104-6.

21. Dean, H. A., I. C. Bailey, and R. Reinking. 1962. Chemical
control of brown soft scale on citrus in the Lower Rio Grande
Valley of Texas. I. Rio Grande Valley Hortic. Soc. 16: 11-21.

22. Dean, H. A., W. G. Hart, and S. Ingle. 1971. Citrus mealybug, a
potential problem on Texas grapefruit. I. Rio Grande Valley
Hortic. Soc. 25: 46-53.

23. Dean, H. A., W. G. Hart, and S. I. Ingle. 1977. Pest management
considerations of the effects of pesticides on Texas citrus pests and
certain parasites. I‘. Rio Grande Valley Hortic. Soc. 31: 37-44.

24. Dean, H. A., and C. E. Hoelscher. 1967. Chaff scale parasite
complex as affected by carbaryl. I. Econ. Entomol. 60: 729-30.

14

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Dean, H. A., and N. P. Maxwell. 1967. Spotting of grapefruit as
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Soc. 21: 35-45.

Dean, H. A., and D. E. Meyerdirk. 1982. Ceroplastes cir-
ripedifonnis parasite complex on Texas citrus. Environ. Entomol.
11: 177-80. "

Dean, H. A., and E. O. Olson. 1956. Preliminary studies to
determine possibility of transmission of tristeza virus in Texas. I.
Rio Grande Valley Hortic. Soc. 10: 25-30.

Dean, H. A., and A. Shull. 1973. California red scale populations
as affected by certain scalecide treatments. I. Rio Grande Valley
Hortic. Soc. 27: 57-62.

Dean, H. A., and B. Sleeth. 1959. Control of fruit russeting in
citrus. I. Rio Grande Valley Hortic. Soc. 13: 63-9.

Ebeling, W. 1936. Effect of oil spray on California red scale at‘,

various stages of development. Hilgardia 10: 95-125.

Ebeling, W. 1950. Subtropical entomology. Lithotype Process
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Fargerlund, I., and D. S. Moreno. 1974. A method of handling
card traps in mealybug, scale surveys. Citrograph 60: 26-8.

French, I. V. 1974. Evaluation of new miticides for control of
citrus rust mite and Texas citrus mite. I. Rio Grande Valley
Hortic. Soc. 28: 112-21.

French, I. V. 1975. Control of armored scale on citrus with non-oil
scalecides. I. Rio Grande Valley Hortic. Soc. 29: 45-51.

French, I. V. 1982. Evaluation of Vendex 4L® and Vydate L® for
suppression of citrus rust mite. I. Rio Grande Valley Hortic. Soc.
35: 121-6.

French, I. V., and E. M. Hutchinson. 1980. Citrus red mite: a
potentially damaging pest of Texas citrus. I. Rio Grande Valley
Hortic. Soc. 34: 107-14.

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3M—4—83