Mealybugs of California with Taxonomy, Biology and Control of North American Species

By Howard L. McKenzie

This title is part of UC Press's Voices Revived program, which commemorates University of California Press’s mission to seek out and cultivate the brightest minds and give them voice, reach, and impact. Drawing on a backlist dating to 1893, Voices Revived makes high-quality, peer-reviewed scholarship accessible once again using print-on-demand technology. This title was originally published in 1967.
This title is part of UC Press's Voices Revived program, which commemorates University of California Press’s mission to seek out and cultivate the brightest minds and give them voice, reach, and impact. Drawing on a backlist dating to 1893, Voices Revived

• Language: English
• Publisher: University of California Press
• Release date: Dec 22, 2023
• ISBN: 9780520338227

Howard L. McKenzie

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Mealybugs of California

WITH TAXONOMY, BIOLOGY AND CONTROL

OF NORTH AMERICAN SPECIES

MEALYBUGS

OF CALIFORNIA

With Taxonomy, Biology, and Control

of North American Species

(Homoptera: Coccoidea:

Pseudococcidae)

Howard L. McKenzie

UNIVERSITY OF CALIFORNIA PRESS • BERKELEY AND LOS ANGELES 1967

The buckram embossment on the cover of this book depicts the Giant Mealybug, Phenacoc- cus giganteus McKenzie.

University of California Press

Berkeley and Los Angeles, California

Cambridge University Press

London, England

Copyright © 1967 by The Regents of the University of California

Library of Congress Catalog Card Number: 67-10279

Printed in the United States of America

To the late

PROFESSOR G. F. FERRIS and the late DR. HAROLD MORRISON, eminent coccidologists for over forty years, and close friends who contributed so much to our knowledge of this family of insects.

CONTENTS 1

CONTENTS 1

INTRODUCTION

ACKNOWLEDGMENTS

SCOPE OF STUDY

LIST OF COLORED PHOTOGRAPHS

ECONOMIC IMPORTANCE

CONTROL MEASURES

CONTROL

Organic Phosphates

Chlorinated Hydrocarbons

Ground Mealybug Control

Miscellaneous Chemical Control

Adversities Caused by Chemicals

Cultural Methods

ECOLOGY

MACRO-ENVIRONMENTAL PREFERENCES

MICRO-ENVIRONMENTAL PREFERENCES

Perennial-Flowering Plants (Excluding Grasses)

Annual-Flowering Plants (Grasses Excluded)

Grasses

Conifers

Ferns

Inanimate Objects

MULTIPLE HOST POSITIONS

ANT ASSOCIATIONS

Benefits to Mealybugs

Benefits to Ants

Strange Aspects of Ant-Mealybug Associations

BIOLOGY Life History, Annual Successions

Oviposition

First Instar Nymph

Second Instar Nymph

Third Instar Nymph

Adult Female

Fourth Instar Male

Fifth Instar Male (Adult)

Parthenogenesis

Instars and Generations

Succession in Mealybugs

CYTOLOGY

GENETIC SYSTEMS

Parthenogenesis

Sex Determination

Chromosome Number

TECHNIQUE

FIELD and LABORATORY METHODS COLLECTING METHODS

Choosing a Location

Collecting on Foliage and Stems

Collecting on Branches

Collecting on Crown and Roots

Collecting on Grass

Collecting on Conifers

Preserve Plant Material

PREPARATION OF SLIDE MOUNTS

Temporary Mounts

Permanent Mounts

MORPHOLOGY and CLASSIFICATION MORPHOLOGY

Segmentation

Head

Thorax

Abdomen

Pores and Ducts

Body Setae

CLASSIFICATION DEFINITION OF FAMILY PSEUDOCOCCIDAE

NORTH AMERICAN GENERA OF PSEUDOCOCCIDAE

FIELD CHARACTERISTICS OF MEALYBUG GENERA

KEY TO GENERA OF

TAXONOMY OF SPECIES

List of California Mealybugs

DISTRIBUTION TABLE

LITERATURE CITED

HOST INDEX

GENERAL INDEX

ADDENDUM

INTRODUCTION

Mealybugs¹ are slow moving insects which, in the female stage, are characteristically elongate-oval, soft, and with distinct segmentation. They are usually thinly or thickly covered with a mealy or cottony wax secretion which often extends from along the sides in a series of short filaments, and with usually two longer ones at the posterior end of body (see kodachrome prints and water color paintings in this book). Their mouthparts are thread like, often longer than the body itself, inserted through the tough tissue or bark to suck juices from the host; and they are among the most serious pests of plant life. They vary in size from very minute young, 0.50 mm, to mature adult females measuring as much as 8.00 mm, or perhaps 9.00 mm, in length. The eggs are usually laid in loose masses of cottony wax or felt-like ovisacs. Some species bear living young. The males, seldom seen, are delicate, winged or infrequently apterous (wingless), possessing two conspicuous long caudal wax filaments. They have abortive mouth parts and take no food.

Identifications of mealybugs in practically all cases are based upon the adult female, since the males are so rarely available. Consequently, in this study the males are excluded from consideration.

Historically, most of the literature on California mealybugs is confined to a few isolated publications. The first article pertaining to this subject was written by Carnes (1907) and entitled The Coccidae of California. It was published in the second biennial report for 1905-1906, of the California State Commissioner Horticulture. In this publication twenty- nine (29) mealybugs species were listed which had been recorded, in the entomological literature of the world, as occurring in California. One (1) of these species had been taken in quarantine, but not established in the State. Eleven (11) of the more important pseudococcid species on the list were described in considerable detail, and two (2) of them

¹ Homoptera; Coccoidea; Pseudococcidae.

were illustrated in ink to show gross external features. Later, Essig (1914) wrote an article entitled The Mealybugs of California, published in The Monthly Bulletin, State Commission of Horticulture, Sacramento, California. In Essig’s article an attempt was made to bring together all the information about this group of insects, with particular reference to those of economic importance. Although special attention was given to the economic forms, mention was also made of the noneconomic species in order that the reader would have a more comprehensive idea of the group as a whole. Ten (10) species were listed by Essig in the noneconomic group of mealybugs; eight (8) species were designated as economic on ornamental plants; while four (4) species were assigned as economic on cultivated plants and fruit trees. Two (2) other species were discussed, but were not classified as either economic or noneconomic. Except for certain photographs which fairly adequately depict certain California mealybugs in life, no detailed illustrations showing specific morphological pseudococcid structures accompanied this publication.

In 1918, Ferris published a much more sophisticated treatment of the subject, titled The California species of mealybugs, printed by the Stanford University Press. This study included some 44 species for the state. Rather precise pen and ink drawings of the penultimate and anal lobe cerarii on the last two abdominal segments of the mealybug were included in this study.

Prior to this more comprehensive treatment of California mealybugs, little had been done to contribute to an accurate identification of species involved. Ferris (1917, p. 5) stated that of the nearly 100 species of mealybugs thus far described from North America, including some 35 from California, not more than three or four are recognizable at all on the basis of the published descriptions if taken apart from their typical host and their type locality.

Until Ferris’ 1918 publication, the additional claim could safely be made that even under most favorable conditions, the identifications of many of our California species could not be accomplished with reasonable accuracy.

In 1950, and again in 1953, Ferris produced the splendid volumes of his Atlas of the scale insects of North America, Series V and Volume VI, the Pseudococcidae (Parts I and II respectively), published by the Stanford University Press. In these volumes there are approximately 250 specific names available for North American species of pseudococcids, these including an indeterminate number of synonyms. Of this number some 89 species are recorded in the Atlas as occurring in California. All the species in the Atlas were magnificently illustrated. Ferris implied that the primary intention of this work was to clarify existing names, rather than to describe new species. In fact, he (1950, p. ill) stated, no search has been made in the available material for new species and much material has deliberately been set aside and omitted from consideration. Only here and there have previously undescribed species been included and these only because they have been involved in the synonymy of other species through misidentification or because they assist in rounding out some group that would be inadequately considered if they were omitted.

In 1960 I published an article on Taxonomic study of California mealybugs, with descriptions of new species, this appearing in Hilgardia, a University of California Agricultural Sciences Publication. The purpose of this study was to describe and delineate new California species of mealybugs, and to comment briefly on the taxonomy of other named forms if necessary. A prediction was made at the time that additional undescribed pseudococcid species in the state were a practical certainty and that subsequent collections, particularly of those forms occurring underground, would no doubt reveal many of the new species which would have to be dealt with later on. Furthermore, several new species collected outside the state were described and included in this study to broaden our concepts of this important family of Coccoidea. It was planned that the material made available in this and four subsequent studies (McKenzie, 1961, 1962, 1964, and 1965), all published in the Hilgardia series, would ultimately be incorporated in a systematic exposition on Mealybugs of California, to appear as a companion piece to my publication (1956), The Armored Scale Insects of California. The Hilgardia series of five studies contains descriptions of 57 new species of mealybugs, including those described in other Western States and subsequently found in California.

ACKNOWLEDGMENTS

I am particularly indebted to Dr. R. M. Bohart, Chairman, Department of Entomology, Davis, for suggesting that a systematic exposition on the mealybugs of California be undertaken as a companion piece to my (1956) publication on Armored Scale Insects of California. Dr. Bohart has also read the manuscript of this book, offering helpful suggestions, especially in the area of the more technical taxonomic problems.

At the outset of these investigations, both the late Professor G. F. Ferris, Stanford University, California, and Dr. Harold Morrison, United States Department of Agriculture, Washington, D. C., offered their wholehearted support of the project. In addition, Dr. Morrison made available distribution and host records of California pseudococcids represented in the United States National Collection of Coc- codea (now the United States National Museum). It is difficult to express how very grateful I am to both Professor Ferris and Dr. Morrison for all they have done, and I only hope that they were well aware of this attitude long before they passed on.

In 1960, officials at Stanford University presented as a gift to the University of California, Department of Entomology, Davis, the entire Stanford Coccoidea Collection accumulated over a period of 40 years by Professor Ferris. Without this magnificent collection to rely on, the present volume would have been infinitely more difficult to complete. Appreciation is again expressed to Stanford University for this splendid gift. In addition, permission has been granted by Stanford University Press for the use of many of Professor Ferris’ original illustrations from his Atlas, Series V (1950), and Volume VI (1953). These drawings were placed in my custody at the time the Scale Insect Collection and Library were transferred to* the University of California at Davis (see pages 3 and 4 for the list of illustrations used).

Mr. R. F. Wilkey, taxonomist, Bureau of Entomology, California Department of Agriculture, Sacramento, has been particularly co-operative in assisting me in these investigations, not only in preparing the necessary slide mounts, but also in helping to screen out and determine the various lots of field collections. The numberous pseudococcid slide preparations he has made for this study have contributed much, because of their excellence, to the accuracy of the final technical illustrations of the involved species. I hereby acknowledge his most willing assistance.

In addition, the California Bureau of Entomolgy has maintained extensive and accurate collection records of mealybugs taken in California, and these data have been extensively used in this publication, with the approval of Mr. R. M. Harper, Bureau Chief.

Mr. Douglass R. Miller, Research Assistant and Graduate Student, University of California, Department of Entomology, Davis has been responsible for collecting the majority of the new mealybug species encountered in these studies. In addition, he has assisted in preparing some of the chapters in this book, as well as some of the drawings depicting certain undescribed species, and has helped in proofreading much of the manuscript. I extend to him my sincere appreciation for his untiring assistance during these investigations.

The chapter on cytology was prepared in collaboration with Dr. Spencer W. Brown, Geneticist, University of California, Berkeley. Actually, Dr. Brown used only a very small part of my material on parthenogenesis in the cytology chapter and, therefore, most of the information on this subject should be accredited to him. Sincere appreciation for his contribution is here indicated.

Drs. Robert L. Usinger, Chairman, Department of Entomology, Berkeley, E. Gorton Linsley, Dean, College of Agriculture, Berkeley, and Alfred M. Boyce, Dean, College of Agriculture, Riverside, examined and unanimously approved the publication of these investigations by the University of California Press. Their support of these studies is most gratefully acknowledged.

Dr. Maurice L. Peterson, University Dean of Agriculture and Director of the Agriculture Experiment Station, Berkeley, kindly made funds available to cover the costs of printing the watercolor paintings and kodachrome prints of various mealybugs included in this book. To Dr. Peterson, and to Dr. James H. Meyer, Dean, Agriculture, Davis, who submitted the original request asking that these colored plates be included in the book, I extend my deepest thanks.

Dr. W. Harry Lange, Department of Entomology, Davis, assisted in taking many of the kodachrome illustrations presented herein. In addition, both Drs. Lange and E. M. Stafford, same department, read the chapter on Control Measures and offered helpful suggestions with particular reference to insecticidal terminology. Dr. O. G. Bacon, same department, has carefully read all the chapters of this book exclusive of the taxonomy section. I gratefully acknowledge this kind assistance.

Dr. L. R. Brown, Department of Entomology, Riverside, and Mr. D. J. Bingham, Nursery Service, California Department of Agriculture, Sacramento, loaned several excellent kodachrome slides of certain mealybug species included in the colored plates of this book. I express my appreciation to them for the loan of these slides.

Thanks are extended to Mr. L. E. Myers, Supervising Inspector, Los Angeles County Agricultural Commissioner’s Office, who loaned me his extensive mealybug collection for use during these investigations.

The Museum of the California Academy of Sciences, San Francisco, California, through the generosity of Dr. E. S. Ross, kindly loaned me the mealybug collection of the late Professor E. O. Essig which is deposited at that institution. This collection has proven especially helpful in this study because of Professor Essig’s early work on California pseudococcids.

The University of California, Department of Entomology, Riverside, recently turned over their entire collection of Coccoidea for deposition in the Museum, University of California, at Davis. I am much indebted to Mr. Harold Compere, Drs. S. E. Flanders and C. A. Fleschner, for this generous gift.

Much valuable information relative to California mealybugs has come from this collection.

Miss June McCaskill, Department of Botany, Davis, is responsible for many of the wildflower and shrub identifications, and Dr. Beecher Crampton, Department of Agronomy, Davis, determined numerous grasses (Gramineae) mentioned in this book. I am deeply indebted to these individuals for this kind assistance.

Since January, 1962, the National Science Foundation, Washington, D. C., has generously provided funds for a grant supporting this study. Continued support of the project is contemplated for all of 1966, and possibly even beyond that time. I express my appreciation to this organization for the grant, which has promoted constructive research on this important subject.

Several delineators have assisted in the preparation of certain pen and ink illustrations, and their initials appear individually, or in pairs on some of them. These individuals are: Mrs. Julia Z. litis, Mrs. Helen Court, Mrs. Mary Foley Benson, and Douglass R. Miller. I sincerely appreciate their help, and especially their concern for this work. Without doubt, they have contributed much to the accuracy of these studies.

Special mention is made of the impressive watercolor paintings of mealybugs reproduced in this book. The artist, Mrs. Mary Foley Benson, is known to many entomologists because of the paintings she prepared of certain economic insects which appeared in the United States Department of Agriculture Yearbook for 1952. Mrs. Benson was formerly Chief Scientific Illustrator for the United States Department of Agriculture. Later she established a studio in Hollywood, California, where she prepared special illustrations for display and sale, as well as other commercial and fine art. Her work has been shown in many art galleries, a few of which include United States National Museum, and Lausburgh, Washington, D. C.; Carnegie Institute of Technology, and Hunt Botanical Library, Pittsburgh, Pennsylvania; Hollywood Association of Artists, and Frances Webb Galleries, Los Angeles, California.

Permission has been granted by Stanford University Press, Stanford University, California, to use numerous illustrations included in G. F. Ferris’ (1950 and 1953), Atlas of the Scale Insects of North America, Series V, and Volume VI, The Pseudococcidae (Parts I and II). Certain species drawings have been slightly altered to include corrections, and these are followed by the symbol (A). The original drawings of figures 64 and 120 were lost. Copies of these illustrations were, however, made from Ferris’ Atlas, and these are followed by the symbol (C). The following list records the species by figure numbers as they occur in the present book:

Fig. 5. Amonostherium lichtensioides (A); Fig. 7. Anisococcus adenostomae; Fig. 8. A. crawii (A); Fig. 9. A. didymus (A); Fig. 10. A. ephedrae; Fig. 12. A.

oregonensis; Fig. 13. A. quercus (A); Fig. 15. Antonina crawii; Fig. 16. A, graminis; Fig. 17. A. pretiosa; Fig. 18. Cataenococcus olivaceus (A); Fig. 20. C. villosa; Fig. 32. Chorizococcus reducta (A); Fig. 33. C. rostellum; Fig. 39. Crisicoccus azaleae; Fig. 40. C. pini (A); Fig. 41. Cryptoripersia salina (A); Fig. 43. Cucullococcus vaccinii; Fig. 44. Discococcus caricis; Fig. 45. D. flabellatus (A); Fig. 46. D. graminis; Fig. 47. D. hopi (A); Fig. 48. D. simplex (A); Fig. 51. Distichlicoccus californicus (A); Fig. 53. D. salinus (A); Fig. 54. Dysmicoccus aciculus (A); Fig. 58. D. quercicolus (A); Fig. 60. D. ryani (A); Fig. 61. D. timberlakei (A); Fig. 63. Ehrhornia cupressi; Fig. 64. Ferrisia virgata (CA); Fig. 67. Heliococcus stachyos (A); Fig. 68. Heterococcus arenae (A); Fig. 69. H. pulverarius (A); Fig. 70. Humococcus atriplicis (A); Fig. 73. H. hilariae (A); Fig. 75. Hypogeococcus spinosus (A); Fig. 76. Misericoccus arenarius (A); Fig. 77. Nipaecoccus aurilanatus (A); Fig. 78. N. nipae (A); Fig. 79. Paludicoccus distichlium; Fig. 82. Phenacoccus artemisiae (A); Fig. 85. P. celtisifoliae (A); Fig. 86. P. colemani (A); Fig. 88. P. dearnessi; Fig. 89. P. defectus; Fig. 93. P. eremicus (A); Fig. 94. P. eriogoni (A); Fig. 98. P. gossypii (A); Fig. 101. P. helianthi (A); Fig. 104. P. lycii; Fig. 106. P. minimus; Fig. 108. P. pauperatus (A); Fig. 109. P. solani (A); Fig. 110. P. solenopsis (A); Fig. 111. Pianococcus citri (A); Fig. 112. P. kraunhiae (A); Fig. 113. Pseudantonina arundinariae (A); Fig. 117. Pseudococcus fragilis (A); Fig. 119. P. longisetosus (A); Fig. 120. P. longispinus (CA); Fig. 129. Puto ambiguus; Fig. 130. P. arctostaphyli (A); Fig. 132. P. bryanthi; Fig. 134. P. cupressi (A); Fig. 145. P. yuccae (A); Fig. 147. Radicoccus kelloggi (A); Fig. 152. Rhizoecus cacticans; Fig. 153. R. californicus; Fig. 154. R. cyperalis; Fig. 157. R. falcifer; Fig. 159. R. graminis; Fig. 160. R. kondonis; Fig. 161. R. leu- cosomus; Fig. 167. Spilococcus andersoni; Fig. 168. S. atriplicis; Fig. 172. S. eriogoni (A); Fig. 174. S. gutierreziae (A); Fig. 175. S. implicatus (A); Fig. 177. S. larreae (A); Fig. 181. S. prosopidis (A); Fig. 183. S. sequoiae (A); Fig. 185. Stemmatomerinx decorata; Fig. 186. Tridiscus distichlii; Fig. 187. T. multiorbis (A); Fig. 188. Trionymus americanus (A); Fig. 189. T. caricis; Fig. 190. T. diminutus (A); Fig. 191. T. dolus (A); Fig. 192. T. festucae; Fig. 196. T. mocus (A); Fig. 197. T. modocensis (A); and Fig. 200. T. smithii (A).

SCOPE OF STUDY

I have tried to present pertinent information about all known mealybug species found in California— 193 species in all. Of this number, 88 species have been named by the author, 32 of which are described as new in the present volume. In addition, the number of pseudococcid genera represented in California totals 35, and of this number, four (4) have been previously described by the author. Some higher-group names have been suggested for certain pseudococcid genera in North America. A complete bibliographical record is included, with reference to the original description of each genus and species; their type locality and host; North America distribution; additional hosts; external features and habitat; recognition characters (morphological structures as viewed through microscope); notes about relationship to other species; and California distribution, with an accompanying outline map showing range in the state. Dichotomous keys to North American genera and species are presented. A common name has been assigned to each California species of mealybug.

This study also contains information relative to the economic importance of mealybugs in California; a resume of control measures as gleaned through a search of the literature; ecology (habitats, ant associations); biology (life history, annual successions); cytology; techniques used in collecting mealybugs and preparing them for critical study on microscope slides; and a detailed account of external morphology of the Pseudococcidae. Each included species is carefully and completely illustrated in an attempt to fill the needs of the systematic entomologist, the technician, and those specifically engaged in biological and chemical control of mealybugs. A distribution table is presented primarily for the benefit of the economic entomologist.

A general index covering all phases of this study is included at the end of this volume. Twenty-one full pages of water color paintings, and four full pages of composite Kodachrome prints, including thirty-six exposures, of certain California mealybugs are provided in this work. It is hoped that these illustrations will enable entomologists, agriculturalists, nursery men, field workers, and home gardeners to recognize our more important mealybugs.

LIST OF COLORED PHOTOGRAPHS

Many of the specimens used to produce the accompanying photographs were collected by various individuals at my request. Some of the photographs were taken by other people and subsequently turned over to me for use in this book. Dr. Leland R. Brown, Entomologist, University of California, Riverside Campus, made available ten of the photographs here used. Mr. David J. Bingham, California State Department of Agriculture, Nursery Service, Sacramento, and Mr. R. F. Wilkey, same department, Bureau of Entomology, kindly turned over to me four Kodachrome slides, and prints from these appear on the following pages. Dr. W. H. Lange, Entomologist, University of California, Department of Entomology, Davis Campus, gave specific instructions necessary to produce many of the accompanying colored photographs. To these individuals, who have so generously participated in this project, acknowledgments are here made.

Most of the colored photographs are enlargements of the insects, and range from approximately 3.5 to 12.5X magnifications. It is hoped that these photographs will help in identifying at least a few of our more common California mealybugs. The species have not been arranged chronologically, but instead are assembled more for the purpose of eye appeal and beauty.

The following list includes specific collection data for each colored photograph:

Color Plate 1

Pianococcus citri (Risso), Davis, Yolo Co., California, February 23, 1960, on Coleus sp. (coleus) (H. L. McKenzie).

Heterococcus pulverarius (Newstead), 8 miles east Tulelake, Modoc Co., California, May 31, 1961, on Poa sp. (bluegrass), (K. G. Baghott).

Chorizococcus lounsburyi (Brain), Pacoima, Los Angeles Co., California, April 6, 1953, on Gasteria Unqua (succulent) (L. R. Brown).

Phenacoccus colemani Ehrhorn, 10.7 miles north Hat Creek, Shasta Co., California, May 23, 1963, under volcanic lava rock, associated with ants (T. R. Haig).

Phenacoccus solani Ferris, Davis (Putah Creek), Yolo Co., California, November 10, 1960, on Compositae (roots) (M.E. Irwin).

Pseudococcus obscurus Essig, Castroville, Monterey Co., California, August 31, 1962, on Solidago sp. (golden rod) (W. H. Lange).

Phenacoccus gossypii Townsend and Cockerell, Davis Campus, Yolo Co., California, September 7, 1961, on Encelia farinosa (incienso) (H. L. McKenzie).

Phenacoccus gossypii Townsend and Cockerell, Exeter, Tulare Co., California, October 4, 1962, on Lantana sp. (lantana) (W. R. Clark) (ovisacs).

Phenacoccus gossypii Townsend and Cockerell, Davis (Campus), Yolo Co., California, September 7, 1961, on Encelia farinosa (incienso) (H. L. McKenzie) (ovisacs and immatures).

Color Plate 11

Anisococcus adenostomae Ferris, 11 miles east Capella, Mendocino Co., California, May 28, 1959, on Ade- nostoma fasciculatum (chamise) (T. R. Haig).

Spilococcus cactearum McKenzie, Berkeley (U. C. Botanical Gardens), Alameda Co., California, November 4, 1958, on Hamatocactus setispinus (cactus) (A. E. Pritchard and H. L. McKenzie).

Spilococcus cactearum McKenzie, Berkeley (U. C. Botanical Gardens), Alameda Co., California, January 20, 1959, on Echinomastus johnsonii (cactus) (H. L. McKenzie) (ovisacs).

Phenacoccus eschscholtziae McKenzie, 2 miles west Yucca Valley, San Bernardino Co., California, April 9, 1963, on Malacothrix californica var. glabrata (D. R. Miller).

Cryptoripersia salina (Ehrhorn), 2 miles south Kneeland, Humboldt Co., California, June 16, 1960, on Danthonia californica (oat grass) (K. Miller and T. R. Haig).

Pseudococcus obscurus Essig, (species with lateral filaments) and Spilococcus cactearum McKenzie, Berkeley (U. C. Botanical Gardens), Alameda Co., California, November 4, 1958, on Hamatocactus setispinus (cactus) (H. L. McKenzie and A. E. Pritchard).

Nipaecoccus nipae (Maskell), Coronado Island, San Diego Co., California, March 6, 1952, on Kentia sp. (palm) (C. O. Eads and L. R. Brown).

Phenacoccus giganteus McKenzie, 12 miles south Shoshone, Inyo Co., California, April 13, 1963, on Fran- seria dumosa (burro-weed) (D. R. Miller).

Phenacoccus giganteus McKenzie, 12 miles south Shoshone, Inyo Co., California, April 13, 1963, on Fran- seria dumosa (burro-weed) (D. R. Miller) (ovisac).

Color Plate 111

Phenacoccus graminosus McKenzie, Napa, Napa Co., California, January 1, 1959, on Lolium sp. (rye grass —sheaths above crown) (overwintering adult females) (H. L. McKenzie and R. P. Allen).

Phenacoccus celtisifoliae (Hollinger), Dunnigan, Yolo Co., California, July 28, 1964, on Photinia arbutifolia (Christmas berry, toyon), (T. Kono and H. H. Keifer).

Nipaecoccus aurilanatus (Maskell), Beverly Hills, Los Angeles Co., California, January 7, 1958, on Araucaria excelsa (Norfolk Island pine) (D. Farrell).

Cataenococcus olivaceous (Cockerell), Lawndale, Los Angeles Co., California, January 24, 1961, on Yucca sp. (Spanish bayonet) (L. E. Myers).

Rhizoecus pritchardi McKenzie, Berkeley, Alameda Co., California, November 4, 1958, on Adiantum sp. (maidenhair fern, roots) (H. L. McKenzie and A. E. Pritchard).

Spilococcus implicatus Ferris, 3 mile north Kneeland, Humboldt Co., California, August 14, 1963, on Sequoia sempervirens (redwood) (T. R. Haig).

Pseudococcus fragilis Brain, Martinez, Contra Costa Co., California, April 8, 1955, on Pittosporum tobira (Japanese pittosporum) (D. J. Bingham and Danielson).

Rhizoecus kondonis Kuwana, Healdsburg, Sonoma Co., California, January 17, 1962, on Prunus domestica (prune roots) (W. W. Wiard and H. McCracken).

Rhizoecus kondonis Kuwana, November, 1961, damage to Medicago sativa (alfalfa) (H. L. McKenzie and V. E. Burton).

Color Plate IV

Chnaurococcus trifolii (Forbes), Truckee, Nevada Co., California, August 26, 1965, on Gramineae (grass) (T. R. Haig).

Anisococcus quercus (Ehrhorn), 8 miles east Alturas, Modoc Co., California, August 29, 1963, on Purshia tridentata (antelope brush) (R. M. Hawthorne and R. C. Hall).

Ferrisia virgata (Cockerell), Brawley, Imperial Co., California, December 31, 1963, on Lantana sp. (lantana) (D. R. Miller).

Scaptococcus milleri McKenzie, new species, 8 miles west Glamis, Imperial Co., California, in sand dunes on Eriogonum deserticola (buckwheat family) (D. R. andJ. F. Miller).

Pseudococcus maritimus (Ehrhorn), Bodega Bay, Sonoma Co., California, August 4, 1963, on Eriogonum latifolium (D. R. Miller).

Anisococcus oregonensis Ferris, 3 miles northwest Spring Garden, Plumas Co., California, July 7, 1965, on Eriogonum umbellatum poly anthum (sulphur flower) (T. R. Haig).

Puto californicus McKenzie, new species, 5 miles north San Bernardino, San Bernardino Co., California, July 23, 1963, on Lotus sp. (D. R. Miller).

Rhizoecus cacticans Hambleton, Berkeley (U. C. Botanical Gardens), Alameda Co., California, November 4, 1958, on Hamatocactus sp. (cactus roots) (H. L. McKenzie).

Puto acirculus McKenzie (immature), Santa Paula, Ventura Co., California, May 22, 1958, on Elymus condensatus (giant rye grass) (L. R. Gillogly and J. L. Weber).

ECONOMIC IMPORTANCE

Mealybugs in California are serious plant pests, and as a result have caused considerable research in the fields of chemical and biological control.

One of the most important California pseudococcid pests over the past half century has been the citrophilus mealybug, Pseudococcus fragilis Brain (col. pls. Ill and XVI). This species was first found in California in 1913 near Upland (Woglum, 1922) and rapidly became a serious pest of citrus to the point that it threatened the industry. An attempt to eradicate the species in this area at that time failed, and it gradually spread along the coast into Los Angeles, Orange, and Ventura Counties. Since that time it has been primarily restricted to the cooler, more humid regions. Injury to host, as is typical with most mealybug species, is caused by extracting plant sap, excreting honeydew which provides a medium for sooty-mold fungus, and production of a cottony wax material on the fruit and leaves. The excretion of sticky honeydew on the host, and the subsequent build up of sooty mold growing in this medium; create an unsightly appearance especially to the fruits, thus causing serious economic loss to the grower.

Chemical control measures directed against the citrophilus mealybug were ineffectual. Biological control, on the other hand, was quite successful. This was first effected by a lady-beetle predator, Cryptolaemus montrouzieri (Mulsant), introduced by Koebele from Australia in 1892. The beetle, in both the adult and larval stages, successfully attacked the mealybugs, but because of the beetle’s high mortality during the winter months in California, it was unable to maintain sufficient numbers to counteract the rapid spring increase in the mealybug population. A successful method of mass rearing of the beetle in insectaries was developed, and this proved to be an effectual means of controlling the pest. The mass rearing and liberation of cryptolaemus, however, constituted an annual program involving considerable expense.

In 1927, Harold Compere found in Australia two species of hymenopterous parasites, Coccophagus gurneyi Compere and Tetracnemus pretiosus Timberlake, which not only attacked the citrophilus mealybug, but were also capable of maintaining themselves throughout the winter months (Compere and Smith, 1932). These parasites gave almost complete control over this mealybug on all of its host plants (Ebeling, 1959).

Pianococcus citri (Risso), the citrus mealybug (col. pls. I and XIV), has been a sporadic pest in the United States since 1879 (Quayle, 1938). In California it is a pest in nearly all greenhouses and nurseries where it attacks a wide range of ornamental hosts. It is considered a serious pest of citrus in many parts of the world. In California it was for years rated as the most important citrus-infesting species until the introduction of the devastating citrophilus mealybug. Heavy infestations on citrus have never been widespread throughout all of the citrus groves, but have been localized. Damage caused by citrus mealybug is of the normal fruit contamination, honeydew, and sooty-mold type. In addition, at least in some strains, this mealybug has an apparent toxic effect on the plant host. On Coleus this damage is usually noted when the medial area along the midrib of the leaves (normally the area of heaviest infestation) turns brown. Chemical control of this insect is amazingly difficult, with parathion giving the best results. In biological control programs, partial control has been attained by a coccinellid predator Cryptolaemus montrouzieri (Mulsant) and a hymenopterous parasite, Leptomastidea abnormis (Girault) (De Bach and Schlinger, 1964).

Pseudococcus maritimus (Ehrhorn), grape mealybug (col. pl. IV), is another species important primarily to grapes and pears in California. This pseudococcid has for some time been confused with another species, Pseudococcus obscurus Essig, and because of this has caused much confusion in the lit-

erature. Until the paper by Wilkey and McKenzie (1961), no one knew exactly what species were being discussed. In California, P. maritimus is found primarily in the central and southern sections, and can be collected from the cool coastline to the hot central valleys. The presence of these mealybugs on the ripe marketed grapes results in serious economic loss to the growers. Heavy infestations cause the grapes to crack, allowing mold contamination (Ebeling, 1959). Present control of this mealybug on grapes is with parathion (Jensen, Stafford, and Break, 1959).

Pseudococcus longispinus (Targioni Tozzetti), the long-tailed mealybug (col. pl. XV), is distributed world wide and is particularly common in America, Africa, and some parts of Europe (Ferris, 1950). This mealybug is often a pest in greenhouses and nurseries, but is also found out-of-doors in warmer areas. In California, the species is most important as a nursery pest, attacking a wide variety of hosts. It has occasionally been reported as a pest of avocados, grapes, and citrus. Specific plant damage is of the usual type. In the fall of 1933, a serious infestation of this mealybug developed on oranges over an area of some 200 acres near Downey in Los Angeles County, California. Although severe outbreaks are quite unusual for this species, some biological control work was done at that time, and partial control has been maintained since with the hymenopterous parasites, Anarhopus sydneyensis Timberlake and Tetracnemus peregrinus Compere (Flanders, 1940). Chemical control is feasible, especially in nurseries.

Phenacoccus gossypii Townsend and Cockerell, the Mexican mealybug (col. pl. I), is widely distributed throughout the United States and Mexico. In California it is a pest of numerous flowering plants in nurseries and greenhouses, and in natural environments. This mealybug, which is most often found on the foliage of its host, apparently causes as much damage to its host as the citrus mealybug, Pianococcus citri (Risso) (Meyers, 1932). Wilting and stunting of the plant host are common effects of heavy infestations. Chemical control is feasible.

Pseudococcus microcirculus McKenzie, orchid mealybug (col. pl. XVII), is a species described rather recently (McKenzie, 1960), but one which has caused many problems to orchid growers before and since that time. It is restricted, as now known, to nurseries where it attacks only orchids. It is found primarily on the roots of its host, but crawls to the foliage and leaf sheaths when infestations become heavy. It is now restricted to California, ranging from the most serious infestations in the Marin County region south to Los Angeles and Riverside counties. Although most infestations have occurred in coastal regions, the controlled environments of the nurseries make even the hot valley regions susceptible. Restriction to California is probably more an indication of heavier collecting in this state than in others, for this mealybug was intercepted on orchids from Florida in 1961. The type of damage is the normal form of unsightly contamination with the production of honeydew during heavy infestations. (See col. pl. XVII). Chemical control is partially successful, but because infestations are Often hidden in the sheaths and on the roots, the mealybugs avoid contact with the chemical.

Chorizococcus brevicruris McKenzie, the shortlegged mealybug (col. pl. VIII), was originally described (1960) from a single specimen intercepted in quarantine at Honolulu, Hawaii, on a succulent, Caralluma neb row ni (Asclepiadaceae), from an unknown California source. In September, 1965, this mealybug was found in a private greenhouse in Sacramento, California where it was causing serious damage to several species of succulents, Huerina spp. and Stapelia spp., belonging to the same plant family as the one intercepted in quarantine at Honolulu (see col. pl. VIII). It was also found on one cactus plant, Myrtillocactus geometrizans, growing near infested succulents. Recent survey indicates that this species is rather widespread in California nurseries in the counties of Los Angeles, Riverside, Sacramento, and San Bernardino. In 1941, it was collected on Stapelia sp. in a nursery in west Los Angeles, California, but was misidentified at that time as another pseudococcid species. The Sacramento grower reports that repeated applications of malathion, used as a drench for potted plants, is a fairly satisfactory control for this mealybug.

Ferrisia virgata (Cockerell), the striped mealybug (col. pls. IV and X), has recently been of some concern to California economic entomologists. Until recently it was not known to occur in Califronia except in minor nursery infestations which were soon eliminated. Within the past few years, however, heavy infestations were noticed on many ornamental plants in Imperial County. This has caused some alarm, because in other parts of the world this species is reported as an important pest, especially to cotton. It is found normally above ground on the foliage where it causes the usual honeydew-sooty- mold-type damage. During severe weather, in Africa at least, it may move to the crown and roots of its host (De Lotto, 1964). In Imperial County a survey of the extent of infestation is presently being conducted by the California Department of Agriculture, Bureau of Entomology. Surveys have shown that the mealybug is found on a wide range of hosts with an apparent preference for lantana, Lantana spp. (Ver- benaceae), popper plant, Rueilia malacosperma (Acanthaceae), blood flower, Asclepias curassavica (Asclepiadaceae), Chrysanthemum sp. (Composi- tae), and that the infestation is fairly localized. Investigations are being conducted to determine the advisability of eradication.

Antonina graminis (Maskell), Rhodesgrass mealybug (col. pl. VII), is another mealybug presently of major concern to economic entomologists in California. This mealybug has been a major pest of many grass species. Rhodesgrass, Johnson grass, Bermuda grass, and St. Augustine grass apparently are preferred hosts, but some 69 grass species have been recorded as hosts in the United States (Chada

and Wood, 1960). It is a very serious pest on Rhodesgrass in the southwestern United States, where it has completely destroyed thousands of acres of good pasture land. Rhodesgrass mealybug is known to infest not only grassland areas but also residential lawns and golf greens. For the most part, this species is confined to the roots and crowns of its host, but attack of the aerial nodes does occur during heavy infestations. It is difficult to determine the extent of damage caused to the host because of the secondary effects of drought, overgrazing, or mowing. Injury is first indicated by the stunting and reduction in the overall size of individual grass clumps, with darkening of the leaves and eventual death of the host plant. Death of seedling plants is known to occur in about three weeks. Because of the serious threat that this mealybug poses to California lawns, pastures, and golf courses, entomologists have been carefully observing its behavior and spread in the state. The mealybug was first collected in Imperial County on October 13, 1957 on St. Augustine grass. On August 10, 1964 it was found in a lawn of Bermuda grass on a residential property at San Diego, California—a distance of some 85 miles from nearest infestation in Imperial County. Control is difficult because of the position of the mealybug on its host, and the use of the systemic insecticides Schradan and Demeton as a drench have proved effective only in certain confined areas. It is too expensive and impractical, however, to use such methods for large acreage infestations (Chada and Woods, 1960).

Phenacoccus graminosus McKenzie, the ryegrass mealybug (col. pls. Ill and XII), is a species located primarily in the central and northern parts of California, ranging from the coast inland to the valleys. It is restricted to grass hosts where it primarily inhabits the grass sheaths. In California this mealybug is only of minor economic importance, but according to Miss Helen M. Brookes, Coccidologist at the University of Adelaide, Waite Agricultural Research Institute, Adelaide, South Australia, the species is of some importance on barley, canarygrass, ryegrass, and wheat in that country. In one instance the mealybugs were living in large colonies among the spikelets of Phalaris tuberosa (bulb canarygrass), feeding on the peduncle rather than on the ovaries. In this case they seem to have been responsible for the failure of many seeds to germinate. In New Zealand its habit of crawling from ground cover onto apple trees, settling around the stem end of fruits, has caused rejection of apple shipments to other countries. No control measures have been directed toward this mealybug.

Trionymus haancheni McKenzie, the Haanchen barley mealybug, was reported by Osborn (1951), and later by McKenzie (1960), as of some economic concern to Haanchen barley grown in the Tulelake area of Siskiyou County, California. Osborn (1951, p.154) reports that in August of that year, the Siskiyou County Agricultural Commissioner’s office at Tulelake submitted specimens of a mealybug reported to be so abundant on Haanchen barley in some fields that combines were being gummed up and clogged at harvest. When visited early in September, harvesting had been completed in the infested fields but large numbers of dead and dried mealybugs were present on the stubble. Large numbers of cottony egg clusters contained unhatched eggs. Broken straws on the ground and some standing uncut at the edge of the field showed evidence of feeding by mealybugs along the stems under the leaf sheaths. Accumulations of thick sticky honeydew secretions were still present. Approximately 15,000 acres of Haanchen barley are planted in this district, located south and west of Tulelake. Gumming of combines at harvest was said to have involved approximately 350 acres. Experimental control has not been directed against this mealybug.

Heterococcus pulverarius (Newstead) (=H.gram- inicola Morrison), the bluegrass mealybug (col. pls. I and XI), has on several occasions become economically important on bluegrass grown for seed in northern California and southern Oregon. The mealybugs are found primarily in the grass blade sheaths, but when infestations become severe they may be exposed on the foliage. Honeydew produced by this species often causes the grass foliage to become quite sticky. When this happens at harvest time, it has been found necessary to first wet the windrows with water spray the day before combining. Chemical control, especially with parathion, has been used to control this mealybug. Cultural practices are also quite effective in holding the species in check.

On certain occasions mealybugs may become rather troublesome, if not serious, household pests. During September, 1963, the fluffy mealybug, Puto echinatus McKenzie, became so abundant on vegetation growing in a residential area at Imperial Beach, San Diego County, California, that large numbers of specimens invaded dwellings much to the terror and dismay of the occupants. The preferred host of this coastal mealybug appears to be Australian saltbush, A triplex semibaccata (Chenopodia- ceae), although during epidemic periods it may attack many other plant species.

A similar situation developed during the summer of 1966, when the white mealybug, Puto albicans McKenzie, reached epidemic proportions on manzanita, Arctostaphylos sp. (Ericaceae), in an area situated approximately six miles southeast of Placerville, El Dorado County, California. As a result of this tremendous population explosion, great numbers of female mealybugs swarmed into homes in this area. Feeble attempts at control were made with no visible results, mainly because only a few plants were treated in an infested area of perhaps several square miles.

Aside from numerous other species of mealybugs feeding above ground and causing economic concern to commercial, subtropical, and ornamental plants, there appears to be an enormous fauna of subterranean species about which very little is known.

Hambleton (1946), in his studies of hypogeic mealybugs, records that two workers, Bunzli (1935) and Weber (1944), have demonstrated the importance of soil-inhabiting mealybugs in the production of certain tropical crops. No less than 10 species of ground mealybugs are associated with ants on roots of Coffea liberica in Dutch Guiana. Apparently, coffee and cacao are infested with so many species of subterranean mealybugs that it would be reasonable to assume that these insects will be found to play a more important role as pests than has previously been suspected.

In California there are three species of groundinhabiting mealybugs of undertermined economic importance belonging to the genus Rhizoecus Kiinc- kel d’Herculais. These species are: Rhizoecus falcifer Knckel d’Herculais, the ground mealybug (col. pl. XXI); R. kondonis Kuwana, Kondo mealybug (col. pl. Ill); and R. pritchardi McKenzie, Pritchard mealybug (col. pls. Ill and XXII). As mentioned in the chapter on Control Measures, the field species are almost impossible to control, whereas in gardens and nurseries flooding with water, or drenching potted plots in certain insecticides, has given fairly satisfactory control.

Collections of Rhizoecus kondonis Kuwana, Kondo mealybug (col. pl. Ill), on roots of alfalfa, strawberry, and in leaf mold with uncertain plant associations, indicate that this species is more widespread in California than previously supposed, and that it is capable of causing serious economic damage to some of these commercial crops.

Collections of Rhizoecus kondonis Kuwana were made during November, 1958, on the roots of alfalfa grown on a ranch eight miles west of Santa Rosa, Sonoma County, California. This mealybug was found aggressively feeding on alfala roots and causing extensive brown areas on killed and stunted plants. By June, 1959, approximately 50 per cent of the stand of alfalfa had been killed by the feeding activities of this mealybug.

The land on which the alfalfa was grown was originally planted to Gravenstein apple. In 1929 the orchard was removed, and from that time until the fall of 1950 it was alternately sown to Sudangrass and oats. In 1951 the land was put into alfalfa and left in that crop for three years. Finally the alfalfa was removed, and each year thereafter, until the fall of 1956, the land was sown to oats. In the spring of 1957 it was again put into alfalfa. The alfalfa was grown on alluvial-type soil near a creek bed. It was nonirrigated, but subterranean water provided enough moisture to promote sufficient plant growth to justify three or four cuttings annually.

The mealybugs were found to be feeding in great numbers just beneath the soil surface and to depths of more than 38 inches (col. pl. III). Small soil samples collected at various depths—8 inches, 12 inches, 24 inches, and 36 inches—were put into plastic bags and brought into the Entomology Insectary laboratory. These soil samples were then placed in four separate Berlese funnel traps. The number of mealybugs (nymphs and adults) recovered from the traps is summarized as follows: 8 inches = 3 specimens; 12 inches = 3 specimens; 24 inches =12 specimens; and 36 inches = 23 specimens. No attempt was made to determine the number of mealybugs per cubic foot of soil in the alfalfa field. It is suspected that alfalfa growing in areas where frequent summer and fall irrigations are practiced may not be so susceptible to attack by this mealybug.

Specimens of this same subterranean mealybug, Rhizoecus kondonis, collected from soil tube cores down to a depth of six feet beneath prune trees growing in the Yuba City area, Sutter County, California, were brought into the laboratory for identification by Dr. K. Uriu of the University of California, Department of Pomology, Davis. According to Dr. Uriu, the orchard from which the mealybugs were taken displayed zinc and potassium deficiency symptoms and, therefore, zinc and potassium plots were established to correct the situation. Apparently, the zinc symptoms were corrected, but the presence of yellow and scorched leaves typical of potassium deficiency was not altered. It is suspected that root injury produced by this mealybug could very likely be the factor in decline of these trees. Preliminary survey indicates that approximately 50 acres of prunes exhibited damage as described above.

This problem of mealybugs on prune roots was brought to the attention of Dr. S. F. Bailey, of the University of California, Department of Entomology, Davis, who is responsible for research on insects attacking deciduous fruits. Dr. Bailey and I visited the affected prune acreage and took hand-dug soil samples to the three-foot level and soil tube core samples to the six-foot level to ascertain the mealybug population per cubic foot of soil. The infested soil samples were then subjected to Berlese funnel trap treatment to recover the mealybugs. The number of mealybugs (all stages) found per cubic foot of soil at various depths in these samples is recorded as follows: one foot =1,708; two feet = 1,245; and three feet = 870. The soil tube core samples taken at depths of four, five and six feet were not broken up before being put into the Berlese funnel trap; this resulted in the soil hardening and trapping the mealybugs before they could emerge. Mealybugs were, however, observed in all these soil samples before they were dried out. Hambleton (1946) recorded subterranean mealybugs commonly found associated with ants, and in their galleries accompanying grass roots, at depths of eight to ten inches below the surface. The information recorded above indicates their ability to feed effectively at greater soil depths than heretofore reported.

Rhizoecus kondonis also appears to be a pest problem in commercial strawberry plantings. Attacked plants show marked stunting, foliage fading, and devitalization resulting in a commercially nonproductive planting.

Rhizoecus pritchardi McKenzie, Pritchard mealybug (col. pls. Ill and XXII), has become a rather serious pest, especially to African violet grown under

greenhouse and nursery conditions. Damage caused by this mealybug to African violet is manifested in devitalization of the plant, resulting in discoloration of the leaves, marked curtailment of blooms until no flowers are produced, and, in cases of heavy infestations, ultimate death of the plant itself (see col. pl. XXII). This mealybug is rapidly spreading across the United States and has been reported as seriously damaging African violet in Maryland and Pennsylvania. Drenching the plants with certain insecticides has been employed as a method of control.

Rhizoecus falcifer Knckel d’Herculais, the ground mealybug (col. pl. XXI), is a common subterranean species present in gardens, nurseries, and greenhouses throughout most of California. Damage caused by this species is general devitalization to complete death of hosts attacked. The mealybug seems to have no particular host preference. Partial control can be initiated by heavy flooding of the infested areas.

In addition to these main problems in California, certain others are known in various parts of the world. Mealybug toxins are rather important in some areas. The pineapple wilt in the Hawaiian Islands involves the pineapple mealybug, Dysmicoccus bre- vipes (Cockerell). It is a serious economic problem to pineapple in that state and has resulted in an extensive amount of research in the past few years.

Some virus diseases are also transmitted by mealybugs. Perhaps one of the most important of these diseases is swollen shoot of cacao. This disease is transmitted by several mealybug vectors, including Planococcoides njalensis (Laing), and Ferrisia virgata (Cockerell). This virus causes excessive damage to cacao trees each year. Mention is made by Newton (1953) of transmission of tobacco mosaic virus by Pianococcus citri (Risso). Also it is recently believed that the pineapple wilt mentioned above as a toxin is in some way connected with a virus.

FIELD KEY TO COMMON CALIFORNIA

MEALYBUGS OF ECONOMIC IMPORTANCE

1. Wax filaments present around body margin 2

Wax filaments absent or restricted to

two or three caudal pairs 8

2(1). Dorsum with at least one longitudinal stripe 3

Dorsum of uniform color, without stripe 6 3(2). With a single dorso-medial stripe 4

With two dorsal sublateral stripes. … 5

4(3). Caudal pair of wax filaments elongate, normally as long as or longer than total length of body Pseudococcus longispinus

(Targioni Tozzetti)

(see col. pl. XVI) (long-tailed mealybug) Caudal pair of wax filaments approximately same length as others, at most one-quarter of total length of body.. Pianococcus citri (Risso) (see col. pls. I and XIV) (citrus mealybug)

5(3). Body contents when crushed bright red; lateral wax filaments easily visible.. Pseudococcus fragilis Brain (see col. pls. Ill and XV) (citrophilus mealybug)

Body contents when crushed gray to light pink; lateral wax filaments minute, difficult to see Phenacoccus gossypii Townsend &

Cockerell

(see col. pl. 1) (Mexican mealybug) 6(2). Wax filaments small; found on grass..

. … Phenacoccus graminosus McKenzie (see col. pls. Ill and XII) (ryegrass mealybug)

Wax filaments elongate; not found on grass 7

7(6). Wax filaments wavy; always found on orchids

.. Pseudococcus microcirculus McKenzie (see col. pl. XVII) (orchid mealybug)

Wax filaments straight; rarely if ever found on orchids … Pseudococcus maritimus (Ehrhorn) (see col. pl. IV) (grape mealybug)

8(1). Body size small; soil inhabiting; antennae elbowed Rhizoecus spp.

(see col. pls. Ill, XXI and XXII) (rhizoecus mealybugs)

Body size normal; foliage inhabiting; antennae straight 9

9(8). Dorsum with two longitudinal stripes and many long crystalline rods. … Ferrisia virgata (Cockerell) (see col. pls. IV and X) (striped mealybug)

Not as above 10

10(9). Legs absent; enclosed in a white felted sac; with a long white tubular filament usually protruding from anal opening in sac Antonina graminis (Maskell) (see col. pl. VII) (Rhodesgrass mealybug)

Not as above. [This half of the couplet involves two species which are very similar in appearance. They both are found in grass blade sheaths. Triony- mus haacheni McKenzie, (Haanchen barley mealybug) is normally found on Hordeum vulgarae, while Heterococcus pulverarius (Newstead) (bluegrass mealybug) is rarely if ever found on the above host (see col. pls. I and XI).]

REFERENCES

Basinger, A. J.

1931. Field key for the determination of some of the common mealybugs infesting nursery stock in California. Calif. Dept. Agr. Bull. 20(2): 189-193, illus.

Bunzli, G. H.

1958. Untersuchungen uber coccidophile Ameisen aus den Kaffeefeldern von Susiman mitt. Schweiz. Ent. Ges. 16(6-7):455-593.

Chada, H. L. and E. A. Wood.

1960. Biology and control of the Rhodesgrass Scale. U. S. Dept. Agr. Tech. Bull. 1221, 21 pp., illus.

Compere, H. and H. S. Smith.

1932. The control of the citrophilus mealybug, Pseudococcus gahani, by Australian parasites. Hilgardia 6(17): 585-618.

DeBach, P. and E. I. Schlinger.

1964. Biological control of insect pests and weeds. Chapman and Hall Ltd., London. 844 pp., illus.

De Lotto, G.

1964. Observations on African Mealybugs (Hemip- tera: Coccoidea). Bull. Brit. Mus. (Nat. Hist.) Ent. 14(81): 343-397, illus.

Ebeling, W.

1959. Subtropical fruit pests. Univ, of Calif. Div. Agr. Sci. Calif. 436 pp., illus.

Ferris, G. F.

1950. Atlas of the scale insects of North America (series V). The Pseudococcidae (Part I) Stanford Univ. Press., Stanford. 278 pp., illus.

Flanders, S. E.

1940. Biological control of the longtailed mealybug, Pseudococcus longispinus. Jour. Econ. Ent. 33(5):754-759.

Hambleton, E. J.

1946. Studies of Hypogeic Mealybugs. Rev. de Ent. 17(1-2): 1-77, illus.

Jensen, F., E. M. Stafford, and R. A. Break.

1954. The Grape Mealybug. Calif. Agr. 8(3):330.

McKenzie, H. L.

1960. Taxonomic study of California mealybugs with descriptions of new species. (Homop- tera: Coccoidea: Pseudococcidae). Hilgardia 29(15):681-770, illus.

Myers, L. E.

1932. Two economic greenhouse mealybugs of Mississippi. The citrus mealybug and the Mexican mealybug. Jour. Econ. Ent. 25(4):891—896, illus.

Newton, W.

1953. Transmission of tobacco mosaic by citrus mealybug. F.A.O. Plant Prot. Bull. 2(3):40. Osborn, H. T.

1951. Insect pest survey. Thirty-second annual report, period ending December 31, 1951. Calif. Dept. Agr. Bull. 40(4): 154.

Pritchard, A. E.

1949. California greenhouse pests and their control. Calif. Agr. Expt. Sta. Bull. 713. 71 pp., illus. Quayle, H. J.

1938. Insects of citrus and other subtropical fruits. Comstock Publishing Co., Ithaca. 583 pp., illus.

Weber, N. A.

1944. The neo-tropical coccid-tending ants of the genus Acropyga Roger. Ann. Ent. Soc. Amer. 37(1):89-122.

Wilkey, R. F. and H. L. McKenzie.

1961. Systematic status of the Pseudococcus mar- timus-malacearum complex of mealybugs (Homoptera: Coccoidea: Pseudococcidae). Calif. Dept. Agr. Bull. 50(4):245-249, illus.

Woglum, R. S.

1922. Control of the citrophilus mealybug. U.S.D.A. Farmer’s Bull. 1040. 4 pp.

CONTROL MEASURES

Mealybugs throughout the world cause a variety of economic problems. The most obvious damage is caused by the sucking habits of these insects. Heavy infestations often cause stunting or death to the plant host. At times mealybugs have toxins and act as vectors of certain viruses detrimental to plant life (Newton, 1953). The young and adults excrete quantities of honeydew which attracts ants and serves as a medium of growth for sooty mold, causing serious smutting of the fruit and foliage. These types of plant contamination are not only important to such crops as alfalfa, citrus, grapes, pears, and avocados, but they are also detrimental to ornamental host plants. Mealybugs are a major problem in California greenhouses and nurseries, where they often cause severe economic damage. The frequent use of insecticides and labor for mealybug control has made their cost to the grower still greater.

It seems surprising that such a delicate soft-bodied insect should be so difficult to control. There are, however, several reasons which may account for this fact. Perhaps the most important factor is the habitat of the mealybug. Mealybugs live in protected areas such as bark cracks and crevices, in grass sheaths, at bases of leaf petioles, and on the undersides of leaves. In addition, other species have the habit of spending their entire lives deep in the soil, protected almost entirely from insecticidal materials. Also the eggs of mealybugs, protected by the waxy filamentous secretions of the ovisac, are almost impossible to reach with insecticides. As a consequence, this is perhaps one of the least susceptible stages of mealybug development to effective control, except for some insecticides that act as both contact and fumigant poisons, i.e., parathion and dichlorovos.

Some mealybugs have been able to develop resistance, while still others are just not affected by certain insecticides.

CONTROL

It is not my purpose to give specific recommendations for mealybug control, but rather to briefly summarize the more recent control measures, resulting from experimentation by other workers, some of which have proven quite effective. Therefore, a resume of mealybug control measures as gleaned through a search of the literature is here presented.

Insecticide trade names mentioned in the following paragraphs are given so that the material may prove more intelligible to the reader. No discrimination is implied with respect to similar or other available preparations.

Organic Phosphates

No one specific insecticide is effective against all species of mealybugs, but parathion comes the closest to fulfilling this aim (Pritchard, 1949). It should be noted, however, that parathion is used primarily in commercial agriculture and is not available to backyard users. Parathion is a contact and stomach poison having some fumigant effect and is used as both a dust and a spray. Madsen (1962) pointed out that, at least for the control of Pseudococcus maritimus (Ehrhorn), dusts were much less effective than sprays. Although this insecticide has been successful in mealybug control, it is extremely hazardous and should be handled with much care.

Because of the hazard of parathion, and because some resistance has been noted in connection with this insecticide (Berry, 1961 MS.), a search was made for a replacement. Malathion, which is primarily a contact insecticide, has proved to be a good substitute for it. Although caution should be used in applying malathion, it is certainly much less dangerous than the first mentioned insecticide. Malathion is used primarily in the control of garden and nursery

mealybugs (Michelbacher, 1959) and is effective in controlling several species, including Ferrisia virgata (Cockerell) (Highland, 1956), Heterococcus pulver ar ius (Newstead) (Dietz, 1960), Dysmicoccus obesus (Lobdell) (Milliron, 1958), Dysmicoccus bre- vipes (Cockerell) (Carter, 1952), and Dysmicoccus cuspidatae (Rau) (Weidhaas and Shaw, 1956). Apparently, Pianococcus citri (Risso) is not effectively controlled with this insecticide (Kriegler, 1957).

Diazinon is another insecticide which is effective at least in the control of Pseudococcus maritimus (Ehrhorn) (Madsen, 1956; Madsen and McNelly, 1960; and Madsen and Westgard, 1962). It is believed that this material is also effective against other mealybugs. Effective both by contact and stomach action, it is used as a dust and a spray, and is not as hazardous as parathion.

TEPP, another organic phosphate, is primarily a contact-type insecticide. It is extremely hazardous and seems to be fairly ineffective in mealybug control when used as a spray (Richardson, 1953). When this compound is used as a smoke, however, it has proven quite successful in greenhouses against immature stages of mealybugs, particularly if a series of applications are made. This method has effectively controlled the following species of mealybugs: Pianococcus citri (Risso), Phenacoccus gossypii Townsend and Cockerell, Pseudococcus longispinus (Targioni Tozzetti), and P. maritimus (Ehrhorn) (Jefferson and Mack, 1953; and Jefferson and Pritchard, 1961).

Dichlorovos (DDVP) is also registered for use in greenhouses as a contact and fumigant control of certain mealybug species.

Several organic phosphates have been used primarily as systemic insecticides. Some of these which have proven effective in mealybug control, in limited cases, are phorate (Thimet®)1 and Di- Syston©. The former has been used in the control of Heterococcus pulverarius (Newstead) (Dietz and Harwood, 1960), Ferrisia virgata (Cockerell), Planococcoides njalensis (Laing) (Bowman and Casida, 1958), and Pseudococcus comstocki (Kuwana) (Abrahao and Manprim, 1958). The latter has been used in the control of Dysmicoccus brevipes (Cockerell) (Carter and Gortner, 1958). The application of these chemicals for control of the mealybugs mentioned above has been either as granules in the soil, as a spray on the soil, or by injection through borings in the plant. Both insecticides are highly hazardous.

Dimefox is another systemic organic phosphate and has been