THE DEVELOPMENT AND USE OF VARIETIES OF BEANS RESISTANT TO CERTAIN PESTS OF LEGUMES,

DISSERTATION Presented in Partial Fulfillment of the Requirements for the Degree Doctor of Philosophy in the Graduate School of the Ohio State University

By JOSE CALDERON GUEVARA, Ing. Agr., M. Sc.

The Ohio State University. 1957

Approved by: CONTENTS Page INTRODUCTION ...... 1 REVIEW OE LITERATURE ...... 4 Insect Outbreaks ...... 4 Food Plant Selection by ...... 11 The Mechanisms of Resistance ...... 14 Cause of Resistance ...... 18 Factors that Affect the Expression or the Permanence of Resistance ...... 22 SYNOPSIS OF THE BIOLOGY OF THE APION PODWEEVIL .... 29 SELECTION OF VARIETIES RESISTANT TO THE APION POD , APION GODMANI WAG...... 30 Seasonal infestation of A. godmani Wagner in Susceptible Varieties ...... 31 Investigation of the Cause of Resistance on beans to Apion godmani Wagner ...... 37 Crossing Program for A. godmani Resistance ...... 42 Classification of Bean Varieties and Lines ac­ cording to Resistance to the ApionPod Weevil .. 49 NOTES ON THE BIOLOGY OF THE CORN MAGGOT IN MEXICO .... 52 Experiments on Seed Color Preference of Hylemya cilicrura ...... 59 Preliminary Selection of Resistant Varieties to the Seed Corn Maggot ...... 61,

ii PRELIMINARY EXPERIMENTS ON THE SELECTION. OF BEAN VARIETIES RESISTANT TO THE POTATO LEAFHOPPER .... 64 Experiments at the University Farm, Columbus,Ohio. 67 Experimental Designs ...... 67 Relationship Between the Potato Leafhopper and Bean Plants ...... 68 Leafhopper Damage ...... 69 Recuperation of the Bean Plant from Insect Attack and Seasonal Differences ...... 72 Effect of Weather on the Potato Leafhopper and the Bean Plant ...... 76 Tolerance of Different Bean Varieties to the Potato Leafhopper ...... 77 Cause of Resistance of Beans to the Leafhoppers .. 82 Method of Estimating Resistance and Susceptibi­ lity of Bean Varieties to the Potato' Leaf­ hopper ...... 84 Results in Resistance to Leafhopper Attack .... 86 DISCUSSION...... 94 SUMMARY ...... 97 GLOSSARY OF ABREVIATIONS ...... 99 REFERENCES CITED ...... 100 ■ " • V " . SELECTED BIBLIOGRAPHY ...... 108 AUTOBIOGRAPHY ...... 117 LIST OP TABLES Table. 1 Per cent of infestation of Apion godmani in two susceptible bean varieties. Chapingo, Mex. 1951. 2 Infestation of A. godmani on three planting dates of two susceptible bean varieties flowering at the same time. 5 A. godmani attack on different pod-number samples of fiayo Gordo bean. Chapingo, Mexico. 1951* 4 Comparison of bean plant characteristics in varie­ ties resistant and susceptible to A. godmani. Chapingo, Mexico. 1952. *” 5 Groups of varieties or lines used in crosses for A* godmani resistance. 1952. 6 yields of bean lines and varieties under apion pod weevil attack. Chapingo, Mexico, 1955* 7 Yield of bean lines and varieties under apion pod weevil attack. Chapingo, Mexico. 1955* 8 Yield of bean lines and varieties under apion pod weevil attack. Chapingo, Mexico, 1955* 9 Classification of lines and varieties of beans according to resistance to the apion pod weevil, Chapingo, Mexico. 1955. 10 Range of variation of apion pod weevil attack in interspecific crosses in beans. 11 Per cent of bean and seedling damaged by the seed corn maggot after a few minutes to four days exposure to the adult flies. Chapingo, Mexico. 1955* 12 Average per cent of seed corn maggot damage on different bean varieties grouped by colors. 13 Bean varieties from Charleston, S.C. resistant to H. cilicrura in Columbus, Ohio. 1956. 14 Bean varieties from various companies resistant to H. cilicrura. Columbus, Ohio. 1956.

iv 15 Bean varieties with rolled type of damage symptoms caused by the potato leafhopper, 16 List of varieties with recuperative capacity after the attack by E, fabae. Columbus, Ohio, 1956, 17 Population of nymphs of the potato leafhopper on susceptible and tolerant varieties. 18 Comparison of total yield (in pounds per plot) of different varieties in relation to resistance to Empoasca fabae. 19 Varieties resistant to the potato leafhopper in Columbus, Ohio. 1956. 20 Bean varieties of low resistance to the potato leafhopper. Columbus, Ohio. 1956.

v LIST OF ILLUSTRATIONS. Fig. 1 Apion pod weevil adult. 2 Relative infestation of apion pod weevil in two susceptible varieties. Chapingo, Mexico. 1951* 5 Per cent attack of A. godmani on two bean varieties. Chapingo, Mex. 19527 4 Rate of increasing in per cent of seed maggot attack. 5 Bean seedling damaged by H. cilicrura. 6 Recuperation of a bean plant after H. cilicrura damage• 7 Adult potato leafhopper (Empoasca fabae Harris). 8 Symptoms of leafhopper attack showing characteristic leaf rolling. 9 Recuperation from leaf-roll type of damage. 10 Stunt type of damage on untreated portion of sus­ ceptible variety. 11 Nymphal population of E. fabae on susceptible and resistant bean varieties. 12 Var. 138-1-14-3-2-M-M a pubescent susceptible variety from Colombia, S. A. 15 A leafhopper-resistant variety Contender (CH). 14 Variety Seminole 5170 (K) resistant to leafhopper attack. 15 Leafhopper-resistant variety Glades (CH).

vi ACKNOWLEDGMENTS

I wish to express my sincere appreciation to Dr. Dwight M. Delong, the Ohio State University for his help­ ful suggestions and criticisms and to Dr. E. J. Wellhausen, Director of the agricultural branch of the Rockefeller Foundation in Mexico for his sponsorship in my studies. Thanks is likewise extended to Dr. George B. Riley, the Ohio State University, for his invaluable assistance in the preparation of this paper and also to Dr. Walter N. Brown, Horticultural Department, the Ohio State University for his

* helpful and timely assistance during the field work in Columbus, Ohio. The author is grateful to Dr. William D. Yerkes, Plant Pathologist, The Rockefeller Foundation in Mexico; Dr. Robert F. Ruppel, Entomologist, The Rockefeller Foundation Colombia, S. A.; Dr. James C. Hoffman, Horticultorist, The Southeastern Vegetable Breeding Laboratory, Charleston, S.C. Asgrow Export Corporation, F. H. Woodruff & Sons, Ferry Morse Seed Co.; Corneli Seed Co.; Rogers Bros. Seed Co. and Atlee Burpee Co. for providing bean seed samples, making the study of leafhopper resistant varieties possible.// : ! Deepest appreciation is expressed to my wife Carmen R. de Guevara for her valuable aid and forbearance in the course of this investigation.

vii INTRODUCTION

"In the Botanical Garden of the National School of Agriculture at Montpellier, France, stands a statue dedicated to Professor G. Foex, commemo­ rating his success in saving the grape industry of France from the damage of phylloxera by re­ sistant varieties from America" (Coons 1951)*

This is perhaps the classic example of insect control by the use of resistant plant varieties and has remained a major means of control for this insect since late in the nineteen century. There are many less well known examples of control of insect damage by the use of resistant plant varieties which have saved enormous amounts of money for farmers. Painter (1951) in his unique book on this sub­ ject "Insect Resistance in Crop Plants", describes the de­ velopment of wheat varieties resistant to hessian fly in Kansas, California and Indiana, which are now being grown on several million acres. One limiting factor in the produc­ tion of cotton in certain regions in Africa used to be the leafhopper Empoasca fascialis (Jac,), but since the selec­ tion of a single plant resistant to the insect and subse­ quent increase of seed from this parent plant, cotton is now grown over thousands of acres, (Parnell 1935)* Varie­ ties of rice, sorghums, potatoes, peas, corn and several other crops resistant to insect attack are being grown successfully by farmers all over the world.

- 1- The use of varieties resistant to insect damage is ac­ cepted universally, hut in countries like Mexico, with an underdeveloped type of agriculture, where insecticides and equipment for their application are very expensive, any biological or cultural method of control is quite welcome. Unfortunately the cultural or biological methods do not completely solve the insect problems in many cases. It is perhaps as an adjunct method to other control measures that the use of resistant varieties to insects is most valuable. This has been demonstrated by Painter, Snelling and others in the case of the chinch bug, where there is a need for insecticidal barriers or other means for protection of young corn and sorghum plants, but re­ sistant varieties of these crops furnish almost the only practical defense against the second and third brood bugs as well as against the few of the first brood that get through the barriers, A combination of resistant varieties and insecticides may be used satisfactorily in the control of the potato leafhopper in beans. With this combination farmers can save about half of the insecticidal treatments they regularly apply each season to beans. After the "DDT storm" (English 1955) there seems to be a modern trend toward better evaluation of quantitative insect losses in agricultural crops. With increasing knowl­ edge of biological and taxonomic information of insects, an integrated insect control program using chemicals, natural -3- agencies and other practices, undoubtedly is the best answer in the immediate future. REVIEW OF LITERATURE

The book by Painter (1951) "Insect Resistance in Crop Plants”, covers the world literature on insect resistance up to most of 1950, contains a great store of information on insect-plant relationship, and is designed in such a way as to be very useful to the researcher. Following more or less Painter's arrangement, a review of the most important literature on insect resistance in the last six years is presented in this paper.

Insect Outbreaks.

There are a couple of papers by two foresters, De Leon and Callahan, dealing with insect outbreaks which illustrate the viewpoint of two schools of thought on plant-insect resistance. The first or De Leon group is very commonly found throughout Latin America and other countries among people who have little training in genetics, ecology, entomology and plant pathology. Comparatively few people working in entomology in the United States are unaware of the achievements in work on disease and insect resistant varieties, De Leon (1954), made the assumption that "it is not primarily the condition of the host but the quality of the causal agent that is responsible for an outbreak”. He bases his generalization on the fact that viruses and bacteria -5- are known to change in virulence. He also points out that the development of so called "resistant” varieties of plants may for the time being reduce losses, but sooner or later the "resistant" variety will become a preferred host. He certainly thinks that rarely, if ever, is there true plant resistance to attack by organisms. That is to say: organisms feed on preferred hosts; if preferred hosts are not availa­ ble they may attack other hosts, and will adjust to the new habitat• Fortunately in the same journal Callahan comments on De Leon's assumptions stressing the facts that the common scientific approach points to a bilateral host-parasite re­ lationship instead of a unilateral one. De Leon, like some others not familiar with breeding and selection for resist­ ance to diseases and pests, misunderstands the concept of resistance as defined by Painter: "Resistance of plants to insect attack may be defined as the relative amount of her­ itable qualities possessed by the plant which influence the ultimate degree of damage done by the insect". Resistance is not an absolute concept, plants and para­ sites are changing elements, but man has the chance of speeding up the change in plants by controlled crossing, obtaining new introductions of plant collections, making innumerable selections and thereby upsetting the relative

j degree of existing equilibrium between plant and parasite. The new equilibrium in the case of resistant plants is in favor of the improved crop. How many years this crop is going to be free of damage, not preferred by the parasite or not affected in yields by the piarasite population depends on many factors and not exclusively the parasite plasticity and biotypes. Perhaps one of the most typical examples of a changing parasite-host picture by genetical recombination of dif­ ferent races is that recorded in the stem rust of wheat. Kanred, a variety resistant to wheat stem rust, was grown in the central United States in 1924. New races of rust were attacking this variety by 1929* Before Kanred was heavily damaged the variety Ceres was released in 1926, planted on several million acres and by 1955 was epidem­ ically attacked. Just a year before Ceres appeared very susceptible, Thatcher began to be produced; still better varieties such as Newthatch, Austin and several others were developed and planted all over the United States. Fifteen years later race 15B of rust started attacking these varie­ ties, but there already existed in commercial production in Mexico other varieties derived from crosses of wheats from Kenya that were resistant. It is believed that much of this problem is created by the development of new races of stem rust attacking genetically uniform varieties, which are often developed as pure lines from single plants. Therefore, a program was undertaken in Mexico in 1952 to develop an indefinite rust-resistant variety. Such a variety must be constituted so that its resistance can be modified to meet changing relative prevalence of different races of wheat stem rust. The procedure to produce such a "composite va­ riety" was as follows: A commercial variety is crossed with a number of varieties carrying different types of resistance. Each single cross is backcrossed several times to the com­ mercial variety. The variety, when distributed commercially, will be a mixture of a number of phenotypically similar lines which are genotypically different for resistance. With changes in races one or several of the lines in the "composite variety" can be removed or replaced, (Borlaug 1953)• Wheat varieties resistant to the hessian fly, Poso 42 and Big Club 43, are so successful in California that fly populations are extremely low. In the variety "Ponca", adapted to culture in eastern Kansas and Oklahoma it has been possible to combine the characteristics of high yield and highest level of hessian fly and leaf rust resistance. Released to the farmers in 1945, it is rapidly replacing other varieties (Painter, 1954). These examples are ^ust a few of the hundreds of resistant varieties now in use by growers. Possible changes in races or biotypes of the para­ site are being detected constantly by testing varieties in different regions or nurseries, so that it has ben possible in large measure to keep ahead of the attack of new para­ site races, or old ones which were almost eradicated but had recurred in new varieties. -8- Callahan also discusses the probable role of a selec­ tive advantage of certain gene combinations in the produc­ tion of an epidemic strain under certain environmental con­ ditions. However he puts more emphasis on the importance of the infinite number of biotic and physical factors in the host-parasite relation. In forest management prevention of outbreaks may be accomphished by changing the environment to reduce the parasite's advantage, by means of selective removal of highly susceptible trees, the conversion of pure stands to mixed stands, or the use of resistant varieties. On these bases he interprets the investigations in popula­ tion dynamics and makes a few generalizations on the sub­ ject of insect outbreaks: Outbreaks are the result of an increased attack potential on the part of the insect, or a de­ creased resistance potential on the part of the host, or both of these conditions. Such poten­ tials are the product of (1) an increase in the parasite population in the frequency of "epidemic ■ genes" through their selective advantage under particular environmental conditions, or (2) dif­ ferential responses to environmental change on the part of both host and parasite, or (3) a combination of these. A very interesting correlation between resistant va­ rieties and outbreaks is discussed by Glen (1954-)* He pre­ sents the phenomena as a very complex matter, but also realizes that even though the factors functions as a complex, certain of them may at a given time or place have a pre­ dominating influence on the population. One of these fac­ tors, perhaps the most important one, is the abundance of -9- food supply of a certain quality. There is no doubt that diseases and pests flourish when there is an abundance of susceptible plant varieties. Man has been selecting since time immemorial in a very rudimentary manner, particularly by mass selection, many varieties with adequate production. However, it is known that mass selection is slow and limited in scope. Recently plant breeders have introduced new methods in crop improvement, particularly the production of hybrids. Improved hybrids and varieties produced by the experiment stations very often are of a high quality and high yielding capacity but many times are selected under the protection of insecticides. Therefore, there is little chance of selecting tolerant varieties or those that will at least help to avoid the sudden occurrence of outbreaks. The knowledge of food preferences in grasshoppers is used in ecological studies and it is now postulated that the annual weeds occurring in unfarmed habitats constitute the major source of aoutbreaks of the lesser migratory grass­ hopper. Small grain crops and grasses which may serve as food do not materially contribute to major outbreaks (Scharff and Donald 19!?4)# Before ending this topic on insect outbreaks it seems appropriate to cite the genetic approach of Frans (1949) on the establishment of equilibrium of insect populations. He thinks that under outbreak conditions, which implies a relaxation of rigorous natural selection, large colonies of insects are built up from small nuclei and inbreeding be­ comes the rule rather than the exception, heterosis is con­ siderably lowered, unfavorable recessive characteristics are fixed in each inbred generation and mortality is in­ creased along with the degeneration of the original stock. Under these conditions, disease and parasite factors reduce the population rapidly. Papers of a general nature have been published in the Yearbooks of Agriculture 1952 and 1953• Packard and Martin (1952) outline the modern methods in obtaining resistant varieties by (1) introductions, (2) selections, (3) cross­ ing and (4) grafting. They explain the definition concepts of resistance, immunity, tolerance, escape, induced re­ sistance, which are the same as defined by Painter (1951)# Quite a few examples of resistant varieties in different crops are mentioned thus giving an overall picture of what has been done in this field. Slightly different terms are often used irrplant pathology to designate more or less the same phenomena. For example, disease enduring varieties is a synonym of tolerant varieties. Practical resistance is defined as a degree of resistance great enough that no serious economic loss results. With the exception of some virus diseases, in plants there is little clear evidence to indicate the existance of antibodies in the sap that destroy the pathogen (Wingard 1953)# A very useful paper for the researcher in plant dis- -11- ease resistance, is that of Stevenson and Jones (1955)♦ ih which the original and the present source of resistance and the mode of resistance is given for most of the important crops. We urgently need a paper of this sort in the work of insect resistance in plants.

Pood Plant Selection by Insects.-

In the last few years several papers have appeared dealing with the subject of insect nutrition and host se­ lection. The most important discussion on these subjects is in the symposium on the physiological relations between insects and their host plants (Dethier, Praenkel, Painter, Kennedy, 1951)* Most of the knowledge in this field is still considered meager in comparison with what must be learned by experimentation and studies on the physiology and bio­ chemistry of plants in relation to insects. American in­ vestigators are inclined to follow the hypothesis that the physiology of plant selection in insects is governed largely by olfactory and contact chemical stimulation by compounds which are effective at extraordinarily low concentrations, and which exert an active behavioral selection. This holds true particularly for most monophagous and oligophagous insects, but polyphagous species have a differential attrac­ tion to various acceptable non-repellent plants due mainly to labile taste preferences. Also oviposition response of many species is considered to be correlated with taste of -12- the host plant by females* Although not enough is known about the food require­ ments of leaf feeding insects, the results of the investi­ gations on different insects indicate that the basic food requirements are essentially similar* Insects need a good quality protein, sterols, a group of minerals, about eight vitamins of the B-complex and certain carbohydrates. How­ ever, recent studies present findings of differences in requirements of various insects for specific compounds. Alkaloids and essential oils of plants are believed to play an important role in the odor response of insects. This assertion is based on the behavior of a large number of insect species tested. The differential preference of insects for different plant tissues, the feeding in certain seasons, differences of abundance or attack encountered in different regions, or soil conditions are explained in part by the dynamic changes occurring in the chemical composition of plants. The presence of biotypes and varying ecological conditions in different regions makes the evaluation of host preferences in diversified habitats difficult. The preference reaction has been placed on a genetic basis in the case of resistance in "Maiz amargo" to the migratory grasshoppers in Argentina and that gene "ag" for locust resistance is linked to gene "p" for pericarp color, making it easy to select resistant plants, (Horovitz and Marchioni, 1952). -13- Attractive qualities may be lacking in some resistant plant varieties. In this case, the insect is reduced to the inefficient trial and error method of host finding* (Painter 1951 a). The food requirements of the european corn borer Pyrausta nubilalis have been investigated by several work­ ers. There is evidence that a growth inhibitor or substance toxic to the corn borer larvae exists in the leaves of some corn varieties. This toxic compound is found in higher amount and apparently for longer periods of time in resist­ ant varieties than in susceptible ones (Beck, Haseman and Painter, 1951)* Brues (1952) gives several examples of feeding prefer­ ences in insects, supporting the hypothesis in his book "Insect Dietary". Dethier (195*0 reviewed insect food habits in relation to the evolutionary process and stresses the fact that there is a vast difference between the food ingested and the nutrients actually required and utilized by the insect. Kennedy in a series of articles (1950, 1951, 1951a) Ibbotson and Kennedy (1950) and Fennah (1951)* working with aphids, propound a dual discrimination theory to explain the sensory discrimination exercised by aphids. They conclude that aphids respond to stimuli strongly as­ sociated or even identical with the nutritionally important materials in the plant. Also there is a reaction of aphids to nonnutritious, attractive or repellent factors ("botani- -14- cal discrimination")• Thorsteinson' (1953* 1955) is also in favor of both theories in food plant selection by insects, pointing out that most of the evidence leads to the ac­ ceptance of the gustatory token stimulus as the primary factor, Lipke and Fraenkel (1956) criticize Kennedy’s dual discrimination theory for lack of enough data relating to the quantities of food taken by aphids feeding on leaves of various stages of maturity. There is a good discussion on insect nutrition in their article as well as a selected survey of the literature.

The Mechanisms of Resistance.

In analizing resistance, Painter (1941) found that it is very useful to divide the phenomena of resistance, as seen in the field, into three components or mechanisms. The three components are interrelated as indicated in diagram 1.

Diagram No. 1.- Interrelated bases of resistance one or more of which is frequently present in resistant varieties.

PREFERENCE ------> ANTIBIOSIS For oviposition, food Adverse effect of plant or shelter. on biology of the insect

^TOLERANCL Repair, recovery, or ability to withstand infestation. -15- The terminology used in resistant varieties has been used for some time by different investigators, without any anthropomorphic or teleological implications. Painter (194-1) defines these components of resistance a s : 1.-Preference (or non preference).- "is used to denote the group of plant characters and insect responses that lead to or away from the utilization of a particular plant or variety". 2.- A n t i b i o s i s .- "is the tendency to prevent, injure or destroy (insect) life". 3.- Tolerance .- "is a basis of resist­ ance in which the plant shows an ability to grow and reproduce itself or to repair injury to a marked degree in spite of supporting a population approximately equal to that damaging a suscepti­ ble host". Antibiosis is subdivided by Dethier (1951) in two phases (a) plants chosen (at random) deficient in required nutrients, (b) Plants with toxic principles. Very interesting studies have been carried out on ovi- position preferences of the wheat stem maggot Meromyza americana Fitch. Preferences for oviposition site caused different levels of infestation in different wheat varie­ ties. The stage of growth of the plant and the intensity of certain wave lenghts are two of the factors which influence oviposition (Horber, 1955)* Preference is a complicated phenomenon. Insects may find their food plants guided by vision, light, gravity and moisture, but temperature and humidity may modify the be- havior of the insects and also have differential influence in certain varieties. Hessian fly females tend to lay more eggs at higher humidities. Age of the plant may influence the expression of genes for resistance. In general sorghum plants are less tolerant to chinch hug when small. The re­ verse is true in the case of corn and the attack of euro- pean corn borer (Painter, 1954). Alfalfa plants are highly susceptible at one season and not at another to pea aphid, Macrosiphum pisi Kalt attack. Resistance in the fall of the year of alfalfa varieties to the pea aphid is correlated to unfavorable food conditions resulting from the biochemical reactions of the plant to low temperature and deficiency of moisture. Under these conditions plant acidity increases, pentoses are formed, lignin is deposited in the cell walls of the pericycle, producing a sclerenchymatous condition and aphids fail to feed in these tissues, (Emery 1946). There are several other factors that influence preference which are not well investigated, one of these is mechanical stimuli. Antibiosis seems to be the most desirable character in the selection of resistant varieties in certain cases, but in many varieties of plants other mechanisms are as impor­ tant as antibiosis. No single component of resistance is ab­ solute, there are complex interrelationships between fac­ tors. In the resistance of several crops a combination of all mechanisms is postulated. In the study of sorghum re- -17- si stance to the corn leaf aphid, Rhopalosiphum maidis six mechanisms of preference or antibiosis were indicated, (Cartier and Painter 1956). 1.- Lack of attraction (or repellence) for winged aphids. 2.- Lack or inhibition of stimulus for birth of nymphs. 5.- Reduction in number of nymphs born. - 4.- Lack or inhibition of stimulus for feeding. 5.- Reduction in the weight of adults produced. 6.- Total or partial inhibition of wing formation in the progenies of apterous females. Many cases of resistance in crop plants to insects are mentioned in Painter's book, along with the methods of in­ sect feeding and possible physiological mechanisms in anti­ biosis. Tolerance is perhaps the least stable mechanisms in re­ sistance and seems to be more affected by environmental con­ ditions acting on the plant. There are different degrees of tolerance which have been utilized by farmers in delaying or eliminating application of insecticides. Little is known about the proccess of tolerance in plants in withstanding fairly heavy damage by insects. It is believed that hybrid vigor increases tolerance, ability for recovery and the proportion of leaf area in relation to the number of insects attacking in several crops. But in other cases it may be that there is a biochemical plasticity in the plant which allows it to a certain extent, to compensate the damage -18- caused by insects or helps to inactivate some toxins in­ jected with the salivary secretion by piercing-sucking insects.

Cause of Resistance.

Some very important concepts are discussed by Painter (1951) in relation to this subject. Investigators often find a correlation between some morphological character­ istics, chemical compound or physiological condition of the plant in analizing the data obtained from a few varieties. However, when a large collection of varieties is compared, the correlations may not hold true. The presence or absence of any substance or structure in resistant varieties is not clear evidence of the cause of tolerance unless the substance or structure is shown to be physiologically vital to the insect. It is very important but not completely necessary to know the cause of resistance to select resistant varieties in plants. Before drawing any conclusions from the studies in the cause of resistance it is necessary to take many factors into consideration. To give and idea of this, there are at least three lines of evidence which should be fully investigated; the following points are transcribed from Painter (1951) •* 1.- Experimental evidence of an intimate relation between the supposed cause and the insect physiology, or insect behavior. -19- 2.- Evidence of complete association between an assigned cause and a given genetic factor wherever this factor occurs, but particularly in segregation following crosses between resistant and susceptible plants. 3.- Statistical evidence in field test in the form of high correlation between the assigned cause and resistance. For practical purposes in the field it is better to know which type of mechanism, preference, antibiosis or tolerance is the most important in the plant-insect rela­ tionship . Some recent reports of investigations on plant resist­ ance which have discussions on the possible cause or cor­ related factor of resistance are briefly reviewed here. Studying the damage of rice on hybrid corn in Ala­ bama, Eden (1952) found that the damage of rice weevil de­ creased as the length of the husk tip increassd and as the number of leaves per husk increased. The effects of these two characters were independent of each other. He also reports on the effect on the hardness of the kernel and the thickness of the pericarp on weevil damage. The re­ sults indicate that for each pound per square inch increase in pressure required for penetration, there was a decrease in weevil damage of almost one per cent. Ho correlation was found between resistance to the ear worm in sweet corn and extension of two inches or more of the husk beyond the ear (Yarnell 1952). Observations made on -20- varieties of sweet corn considered susceptible and resistant to the european corn borer presented no correlation between sugar content and infestation, nor between sugar content and survival of larvae (Turner, 1951). Rescue wheat is a solid stemmed variety resistant to the wheat stem sawfly, Oephus cinctus Norton. Susceptible varieties are hollow-stemmed (Forstad, 1951). Solid stemmed Rescjie is not uniform in this character; 19 categories of solidness were recorded (Callenbach, 1951). Roberts (1954) considers solidness of stem in Rescue to be one of the factors contributing to the resistance to C. cinctus due to the probability that the genetic factors in the wheat re­ sponsible for egg survival differ at least in part from those responsible for the survival of the older larvae and also from those that determine the degree of infestation. Additional studies of Khanna (1949) on the sugar cane top borer, Scirpophaga nuvella, in India indicate that there is no correlation between the hardness of the leaf midrib and insect infestation. However, Verma (1950) still thinks the structure of the midrib is important in the resistance to this pest. Bennet (1954) found a direct corre­ lation between the internodal structure of the needles in pines, which produced greater or lesser resin flows and susceptibility to attack by insects. Dense pubescence in some cotton varieties seems to be associated with thrips resistance, (Ballard, 1951). Type -21- and density of hairs on the lower surface of the midrib of the cotton leaf are associated with resistance to Jassids, (May, 1951)* Three South American varieties of cotton proved to be highly resistant to artificial infestation of stem weevil, Pempherulus affinis. This resistance seems to be correlated with the ability to grow rapidly and the retardation of the development of the pest in the larval stage by the release of a gummy exudate in affected re­ gions. (Dharmarajulu, 194-8). Johnson (1955) reports his observations on the attack of common beans, Phaseolus vulgaris L. by Aphis craccivora and describes how "the aphid nymphs became impaled on the hooked epidermal hairs of the leaves with the subsequent bleeding starvation, exhaustion and high mortality'1. The confinement of Retithrips syriacus on the upper or lower side of the leaf of castor bean or cotton is believed to be related to the stomatal frequency. (Ananthakrishnan, 1955). The smoothness and curvature of beans are the impor­ tant factors in preference for oviposition of the weevil (Ishii, 1950)* Resistance to Atherigona indiea M. depends on- the early formation of irregular shaped silica deposits in the epider­ mis of the leaf sheath in sorghums (Ponnaiya, 1951)* Studies of the behavior and damage by Aphis fabae on Vicia fabae in the greenhouse show that infestation depends on the developmental physiology of the whole plant and the -22- differences of population density on leaves of different ages were due largely to the preferences exercised hy the apterous females, (Ibbotson and Kennedy, 1950). Another in­ stance where the physiological state of the plant is impor­ tant in resistance is that reported hy Arenz (1951) in the attack of Myzus persicae Sulzer on potatoes. Quantitative differences in odor between two tested varieties seem to constitute the main factor of attack by the bean aphid, Doralis fabae Scop, on Vicia fabae. Oviposition of potato depends on the equilib­ rium of the carbon/nitrogen ratio, on an optimal level of certain constituents, especially glucose, and the presence of stimulating elements such as lecithin in the potato plant, (Grison, 1952). McBean (1951) reports a correlation' between protein content of barley varieties and grasshop­ per damage in tests with moderate infestation. Beard (1951)» comparing aphid-susceptible recessive segregates of corn with inbred lines treated with maleic hydrazide, points out that genetically controlled factors must be responsible for differences in aphid attack. Both segregates and treated inbreds were very similar in appear­ ance.

Factors that Affect the Expression or the Permanence of Resistance..

Expression is governed by both plant and insect fac- -23- tors. Plant factors involve tolerance, antibiosis and ge­ netic composition. Insect factors are considered to be host preference, insect habits, insect life cycle, insect popu­ lation, density and biotypes. Environmental factors are discussed in detail by Painter (1931)* However, in this paper only the latest references on some of these subjects will be mentioned. The ways in which an insect species reacts to par­ ticular environmental conditions have been determined for a few insects under controlled conditions. The corn leaf aphid showed less discrimination between resistant and susceptible sorghum varieties at higher temperatures (above 110°F.) than at lower temperatures. The mortalities of pea aphid at moderate or lower temperatures varied in different groups of resistant varieties. Wheat varieties resistant to the hessian fly have been observed to harbor more insects at high temperatures when the stems were elongating rapidly. The influence of humidity, age of the plant and season of the year (Painter, 1954) have already been mentioned under the discussion on preference. Pre­ cipitation and irrigation greatly influences tolerance. Plants grow more rapidly producing more leaves in a short time, diminishing the proportion of insects per leaf sur­ face under optimum or high moisture conditions. This has been observed in many crops; in cotton attacked by leaf- hoppers (Sloan, 1958) in alfalfa, (Wilson, 1955) and in -24- beans as reported in this paper. Mixed forest associations of balsam fir, white pine, spruce and maple or white pine, birches, aspens and maples are little attacked by insects, (Graham, 1951). Ecological factors may affect the plant, the insect, or the insect- plant interaction. "Lack of pathogenicity in a new host may sometimes be explained as a lack of evolutionary adap­ tation to the new host on the part of the parasite, rather than adaptation of the host toward a toleration of the parasite" (Allee, et al 1949). Most recent reports on the effect of fertilizers in the plant-insect relationship refer to the attack of aphids. The application of fertilizers to certain cabbage varieties reduced the infestation of the cabbage aphid Brevicoryne brassicae L. (Bobunskaia, 1953). Garden peas grown on soils severely deficient in any of the major ele­ ments (H, P, K, Ca, &Mg) were more injured by Macrosiphum pisi Kalt than plants grown on soils of good fertility, (Barker, 1951). The nitrogen content of a variety suscepti­ ble to the pea aphid was quantitatively higher than on two resistant varieties (Maltois, 1951). Arant and Jones (1951)» worked with green bug populations on oats, trying to find the effect of lime and fertilizers on aphid infestation. They found that nitrogen in general had a negative influ­ ence on insect infestation and lime applications also caused a reduction in the infestation. Ho significant dif- -25- ferences were obtained in reproductive capacity of the po­ tato aphid,Macrosiphum solanifolii Ashmead, on potato plants growing on various fertility plots. European corn borer showed a slightly faster growth on plants having a bal­ anced diet than on plants with deficiences on nitrogen, potassium or potassium and phosphorous (Taylor, et al„1952). Populations of mites, Tetranychus telarius L., reared on cucumber in nutrient solutions, were doubled when the concentrations of nitrogen was doubled. There were also in­ creases in mite population due to interaction of nitrogen and potassium (Le Roux, 1954-). "Potatoes grown in refined compost are to a high de­ gree immune to the Colorado potato , but rather sus­ ceptible in soils with very poor humus content and ruined structure of the soil" (Schaerffeuberg, 1955)* There was an indication that adult potato leafhoppers tend to migrate to healthy vigorously growing alfalfa plants in the advanced stages of boron deficiency in untreated plots (Medler and Albert, 1953). Two papers report the use of colchicine for doubling the chromosome number in interspecific crosses, to obtain insect resistance (Pearson et aL, 1951)(Krishnamurti, 1951). Insect biotypes may influence the expression of plant resistance. Recently G-allun (1955) reported the existance of three biotypes of hessian fly in Indiana. He also pre­ sents their differential reaction on five wheat varie- -26- ties. Suneson and Bernarr (1953) suggest the possibility of a different biotype of hessian fly on southern California. The best work on insect biotypes, so far as I know, is that of Cartier and Painter (1956). Two biotypes of the corn leaf aphid Rhopalosiphum maidis Pitch, were studied in relation with the resistance of sorghum varieties. The bio­ types were characterized by differences in fecundity, weight, development of the wings, mortality, restlessness and other minor characters on the resistant and susceptible varieties of each biotype. The authors discuss the possibil­ ity of development of resistant varieties to several known biotypes. Very little work has been done on varieties of beans resistant to insects. Strand (194-3) made interspecific crosses between Phaseolus vulgaris and Ph. mungo at the Tennessee Agricultural Experiment Station. Some of the se­ lections were sufficiently tolerant to the mexican bean beetle to produce dry seeds without the use of insecticide for beetle control even in seasons of severe infestation. However, these selections had poor agronomic characteris­ tics. Cattier (194-8) tested 10 varieties of beans for field resistance to the , obtectus Say, and found fairly good resistance in the varieties Refugee, Perfect, Red Mexican and Small White. Lefevre (1950), work­ ing with the same species tested several varieties in storage and found only the variety Wulma with 95% of sound -27- seeds after 12 months of storage. At the Experiment Station of Puerto Rico (Anon. 1939) some observations were made on the tolerance of a group of lima beans to the leafhopper Empoasca fabalis DeLong, The large seeded varieties were infested with leafhoppers but not injured and the small seeded varieties were heavily damaged. Beyer (1922) was one of the first in reporting the varietal reaction of beans to the potato leafhopper. He observed that the Pea-bean, Wells, Red Kidney and other va­ rieties showed a marked degree of resistance while the bush lima bean varieties were slightly resistant, snap bean was susceptible and pole type highly susceptible. In a test carried out by G-ui (194-5) at the Ohio Experiment Station with 83 samples of beans it was found that lima beans were the least densely populated by the potato leafhopper, fol­ lowed by the Refugee type varieties. The rest of the varie­ ties had heavy populations, particularly the Tennessee greenpod variety. Pig. 1.- Adult Aplon pod weevil. (Natural size 3 bub* ) SYNOPSIS OP THE BIOLOGY OP THE APION POD WEEVIL

The apion pod weevil Apion godmani Wagner shown in Pig. 1, is an important pest of beans in Mexico. Distribution is not definitely known, but it occurs in the central plains, high valleys, and the state of Veracruz on the gulf coast. In some regions of the state of Michoacan in central Mexico it seriously limits bean production. This pest does not at­ tack fully ripened, dried seeds and therefore is not a menace as a stored grain insect. Adults appear in fields when the beans are in bloom and feed on the tender young leaves. However, this feeding does not cause appreciable damage. The females oviposit in pods which are about one to two inches long. They first puncture the pods with the rostrum, then insert the ovipositor into the hole thus made and lay the eggs in the endocarp of the pod. One weevil larva usually destroys only a portion of the seed. The life cycle of this insect from egg to adult follows closely the development of the beans from flowering until maturity. Therefore, the complete cycle is accomplished in six to seven weeks. So far, it has been impossible to rear successfully the apion pod weevil in the insectary or greenhouse. Per­ haps when we know where this pest overwinters it will be possible to keep it the year round for testing on seed­ lings . -29- SELECTION OF VARIETIES RESISTANT TO THE APION POD WEEVIL (APION GODMANI WAG.)

During 1945-50, biological studies and experiments for control of the apion pod weevil and other bean pests were carried on at the Agricultural Experiment Station at Cha- pingo, Mexico. At the same time observations on resistant varieties were reported (McKelvey, et al 1951)• Prom 1951 to 1955 "the work on resistant varieties to Apion godmani was continued, selecting the varieties from.new collections and also examining the selections from crosses made by the personnel of the Genetics Department. The method used in selecting the varieties for Apion resistance was based on the examination of 50 randomly collected pods from each line or variety. The data recorded were: number of attacked pods and number of insects. Up to 1950 the varieties Puebla-52, Hidalgo-6, Hidal­ go-24-, were selected and in 1951 the varieties Chiapas-92, Oaxaca 3, Oaxaca-9, Puebla-5, Puebla-55, Guerrero 8, Guate­ mala-33, Guanajuato-20 and Veracruz-10. All of these varie­ ties had less than 0.2 insects per pod. In 1952, 328 lines in the F-4- generation were examined for insect resistance. The material selected for future work had an infestation of 0.04- to 0,30 insects per pod. Additional selections were made on the yield trial plots, although the compared varie­ ties were being treated with insecticides. In 1953 about two hundred varieties of new introduc-

-30- -31- tions for classifications studies were graded for apion resistance. All the introduction material was treated with DDT, but even so, there was a lot of variation in insect attack in different varieties. One of the best varieties obtained from this collection had the code number BAP 88B. Again in 1954- a few selections were made. This time insec­ ticide applications reduced the pest to very low numbers making it almost impossible to differentiate the range or degree of infestation. The same year a natural cross be­ tween a canario type bean and unknown black bean was se­ lected by seed color and resistance to A. godmani. Most of the segregates had the canario dominant habit of bushy growth and very early maturity. Most of the material selected for apion pod weevil resistance up to 1954- did not have high yields, except the varieties: Rocamex 1, a yellow seed; Hidalgo 12-A-l, black; Puebla-2, black; and EAP 88B, yellow.

Seasonal infestation of A. godmani Wagner in suscep­ tible varieties.

In 1951 ♦ evaluating the data of the last experiment on the biology of A. godmanit important information was obtain­ ed about the percentage of infestation of this pest in two susceptible varieties differing in every respect, except susceptibility. Also a more accurate method of comparing resistant and susceptible varieties was devised. Twelve-row plots 55 feet long, replicated four times, were planted with Canario and Bayo Gordo, (two susceptible varieties) at two week intervals from April to September. Only six plant­ ings were able to develop green beans suitable for examina­ tion of Apion infestation during the season. About each week from July 51» one hundred pods were collected at random from the eight inner rows of each plot. Bach plant­ ing date was, therefore, sampled as soon as the larvae could be seen in the pods until seed maturity. The infes­ tations per 100 pods are summarized in Table 1. -53-

Table 1.- Per cent of infestation of Apion godmani in two susceptible bean varieties. Chapingo, Mex. 1951'. Insects per 100 pods Becord date Bayo Gordo ______Canario July- 31 12 3 August 2 1 2 .5 3 n 7 15 22 ir 14 29 33 n 21 34 32 ir 28 48 34 September 4 49 38 rt 11 47 35 ii 18 49 47 it 25 48 57 October 2 57 45 fl 9 55 54 If 16 41 46 ft 23 50 48 II 30 47 54 November 6 56 7 4 .5 -3*~

60

50

40

30

20

10

July Sept. Oct.

Fig. 2.- Relative per cent of infestation of apion pod weevil in two susoeptible varieties. Chapingo, Mexico, 1951* m m ^

These data are presented graphically in Pig. 2. As can he seen in this graph, the difference in infestation of the two varieties through the season is not too great. One fac­ tor that influences the variation in the attack by weevils in these two varieties is the blossom time, which is earlier in the variety Canario than in Bayo Gordo. This difference in earliness of bean maturity accounts for an unequal at­ tack of the weevils on the small tender pods. If only the planting dates that flowered at the same time are compared, more uniform, data is obtained. In Table 2 these varieties are compared at three planting dates in different months which produced flowers at the same time.

Table 2.- Infestation of A. godmani on three planting dates of Two suscepti­ ble bean varieties flowering at the same time. Insects per 100 pods. Planting Bayo Gordo Canario

August 61.6 65.5 September 57.0 54.5 October 50.0 35.7 ‘ -36- It was found that calculating the per cent of attacked grains instead of the number of insects per 100 pods, yield data appears more uniform. Also this seems to be a better index of yield loss and can be determined easily even after the weevils have emerged from the pods. Therefore, most of the classification of varieties in the following experiments is based on per cent of attacked seeds particularly in the selection from crosses. To determine the best number of pods to collect in each sample and also to find out the percentage of infes­ tation and be able to discard the susceptible varieties on the basis of maximum infestation, records were kept on the variety Bayo Gordo examining different number of pods per sample. In Table 3 it is apparent that 100-pod samples demonstrate the maximum insects per pod and also the largest percentage of grains attacked. Therefore,100 pods seems to be a good sample size with maiximum opportunity for discard­ ing susceptible varieties.

Table 3.-A. godmani attack on different pod-number samples of Bayo Gordo bean. Ghapingo, Mexico. 1951* Per cent Pod-number Insects attacked sample per pod seeds. 23 1.64 28.94 50 1.96 34.64 100 2.38 40.48 200 1.80 30,33 -37- Ihvestigation of the Cause of Resistance on Beans to Apion godmani Wagner.

In 1952 a field experiment was designed to try to gain some information on the cause of resistance of beans to the apion pod weevil. In the high valleys of Mexico the only varieties adapted, with commercial value, are of the bush or semi-pole type. Bush beans generally mature rather early; semi-pole are usually intermediate; pole tropical or sub­ tropical are late in these regions. In this experiment the varieties were selected for comparison on the basis of days required for maturity as shown in Table 4. Thus, Hidalgo-6 a resistant variety, has the same number of days to maturity as Mexicor-9 a susceptible variety. Also Puebla-32, a resist­ ant variety, has the same number of days to maturity as Za­ catecas-9, Bayo Gordo and Canario were included merely as checks. Canario is also the earliest commercial variety in the valley of Mexico, Each plot had 12 rows 36 feet long in a randomized block design with four replications. Eight planting dates were seeded from May to August, but only three planting dates reached maturity. Therefore, only in these plots can a comparison be made. The information gathered in this ex­ periment is presented in Table 4. The average total number of leaves per plant was determined only once, examining 10 plants taken at random in each plot. The average number of pods 1 to 3 centimeters long was obtained by counting and measuring the pods on 10 plants per plot in three consecu­ tive weeks. The pH of the pods was obtained by grinding them and analyzing the brei with an electric potentiometer. The pubescence of the pods was determined with the binocular microscope.. Just before harvesting 100 pods were collected at random in each plot to get the percentage of attacked grains. Table 4.- Comparison of bean plant characteristics in resistant and susceptible varieties to A, godmani, Chapingo, Mexico. 1952

Growth Average Average pH in Pod Blossom Percent Percent VAriety habit Earliness N“ of N° of pods pubes­ color rust grains leaves pods cence attacked 1-3 cm.

Hgo-6 semi­ semi- 37.5 52.5 6.10 S.S* purple 50-80 2.05 pole ear;Ly 1. Mex-9 semi­ s e n j l - 36.5 25.3 6.0 s.s white 50-80 7.47 pole early

Pue-32 semi­ inter­ 50.8 50.6 6.0 s.s purple 25-50 2.74 pole media

Zac-9 semi­ inter­ 39.0 46.2 6.1 . S.A** white 5-10 8.01 pole media

Bayo semi inter­ 39.6 39.1 6.05 S.A white 25-50 10.04 Gordo pole media

Canario bush early 13.9 17.0 6.05 S.A white 0.0 26.24 j

*S.S - Short & scattered *~*S,A - Short & abundant

I vw vO I —4-0— By examining the data of Table 4 and also interpreting the information obtained from large collections, no rela­ tion can be found, up to the present time, between the re­ sistance of bean varieties to A. godmani and the charac­ teristics so far compared. In the preceding experiment no positive results on the cause of resistance could be found, however some of the data obtained can be used to illustrate the relative infestation of A. godmani through the season in a resistant and a susceptible variety with the same number of days to maturity. This information is presented graphically in Big. 3* In this graph it may be seen that the resistant variety is less infested at any planting date through the growing season. Zacatecas-9

2 0 - % Puebla-32

1 5 -

10 -

5 -

Hay 16 I June 2 June 1? Planting Dates Pig, 3«- Per cent attack of A. on two bean varieties* Chaplngo, Hex* 1952. -42- Crossing Program for A. godmani Resistance.

The varieties used in crosses for resistance to the apion pod weevil may be grouped in four classes. These classes appear in Table 5.

Table Groups of varieties or lines used in crosses for A. godmani resistance. 1952. Resistant Immune Improved Triple varieties Var. varieties cross. Hgo-6 Hgo-15A Hgo-14A-3 $(Pue-lB3 x Hgo-15A) Pue-32 Pue-57B3 Hgo-12A-l Hgo-24 Tlax-2-l-C Roc-1 Pue-2 Roc-2 Roc-3 Zac-4-A-2 Hgo-38A-l Canario (Check)

* c = Canario. All the varieties in the resistant group are pinto beans except Puebla-2 which is black. These varieties may be used as male or female parent when crossed with im­ proved varieties. The immune group are of the species PhasePlus multiflorus. These beans are usually self- sterile, because of their cross pollinization, they are not pure lines and segregate to different types when selfed. This group can be used successfully only as male parent. The percentage of interspecific crosses obtained is ex­ tremely low and many times carry lethal genes. The group of improved varieties, some of them already in commercial pro­ duction, released by the Experiment Station at Chapingo, -43- Mexico was crossed with the resistant or immune group. Ca­ nario is a well adapted v a r i e t y throughout the country and has been used extensively in crosses due to its quality, earliness and resistance to some diseases. However, it is very susceptible to apion pod weevil. The last group of lines c(Pue-lB3 x Hgo-15A) were used to make back crosses with Canario (c) in an attempt to select for Canario type with insect resistance. In order to have enough pollen available for crossing, the varieties were planted in the greenhouse on three differ­ ent dates, 10 days apart. Before making the crosses a daily list was made of the total number of buds available in the varieties ready for crossing; with this list it was possible to make a plan of the best combination. Crosses were only made from 9 A.M. to 1 P.M. every day because the pollen was in better condition during these hours, probably due to dif­ ferences in temperature and humidity in the greenhouse. Three hundred seventy one simple crosses were made in the fall of 1952 among the groups listed in Table 5* Only 141 produced seed to be planted in the greenhouse in the spring of 1955* After discarding all the crosses with lethal genes, and all of those which were doubtful crosses only 55 remained to be planted in the field and the greenhouse simultanously in late summer of 1953. The plants in the field were killed by an early frost but some of the early ones already had well developed pods that were examined for weevil infestation. —ZL/1—I I . The procedure employed to eliminate the non-possible crosses in the F-l generation was as follows: Inspection was made on the color of different structures; red and purple flowers dominate pink and white. Purple stems dom­ inate green colored stems. Semi-pole type dominates bush type. Black seed dominates other colors. The character of hipogeus .cotyledons in Phaseolus multiflorus is of incom­ plete dominance. The F-2 plants produced F-3 seeds which could be examined for shape and color. At least in this group of crosses the dominances listed held true, so it was possible to separate the real crosses without too much difficulty. All the seed obtained from the greenhouse planting plus the F-2 seed reserves were planted in the field in 1954-. As late as the F-4 generation in some of the crosses excessive variation in color on the seed coat appeared. One of the extreme examples of this color segregation was obtained in the cross Rocamex-3 x Hidalgo-6. Segregates of this cross presented a range of 21 different seed colors. This heterogeneity in colors seems to be one of the most important problems in selecting for insect resistance in beans because in Mexico beans are consumed mostly as dried beans. Local preferences make it necessary to select for color type as well as resistance and many agronomic charac­ teristics. After eliminating 41 crosses which were very suscepti- -45- ble to A. godmani, 65 lines were left. The seed from each cross was classified, "by seed coat color resulting in 258 seed groupings. Seventy seven of these groups were increas­ ed in the winter at Jalostoc, Morelos, and in the green­ house in Chapingo, Mexico. In 1955 three yield tests plots were planted, using plots of three, two and one row, six meters long, the number of rows depending on the amount of seed available. The experimental design was a randomized block with four replications. All of the lines with limit­ ed available seed were planted for increase and observa­ tion. Each plot in the yield tests was separated from the others by a row of Canario beans, because this variety is one of the most susceptible to A. godmani. At harvest the total plot was threshed, cleaned and weighed individually. The yields of these plots are recorded in Tables 6, 7 and 8. Prom these Tables it can be seen that most of the resistant varieties have the highest yields. The majority of the improved varieties, selected under treatments with insecticides, have very low yield due to their susceptibili­ ty to the apion pod weevil. However, some of the improved commercial varieties carry resistance to A. godmani. Such is the case with the varieties Amarillo-154-, 155» 156 and Negro-150. -46-

Table 6.- Yields of bean lines and varieties tinder apion weevil attack. Chapingo, 1955* (Grams per 3 row plot;

Variety (1) Average yield Reaction

(Zs c t 4A-2 x HgOrr6)-l .964 Resistant Hgo-12A-l Check .879 it (Ego-24 x Hgo-12-A-l)-l .869 n (Hgo-6 x Hgo-14A-3)-l .809 it Amarillo 155 (Commercial) *795 it Pue-2 x Canario .787 11 it (Ego-24 x Zac-4A-2)-l . 7 8 2 (Hgo-12A-l x Pue-32-l)-l .751 It (Roc-1 x Pue-1B3 x Hgo-15A)-l .751 II Zac-4A-2 Check .745 II II ITegro 150 (Commercial) . 6 7 6 (Roc-2 x Pue-32)-l .674 11 (Pue-32 x Zac-4A-2)-l .600 Tl Amarillo 155 (Commercial) .550 ? (Zac-4A-2 x Hgo-24)-l! .550 Resistant (Pue-2 x Hgo-12A-l)-l .510 II (Pue-2 x Hgo-14A-3)-l •4-77 II Bayo Gordo 159 (Commercial) ,420 Susceptible Bayo 160 (Commercial) .375 If Bayo 164 (Commercial) .280 rr ITegro 152 (Commercial) .244 H

(1) For all abbreviations of variety names consult glossary of abbreviations. -47-

Table ?•- Yield of bean lines and varieties under apion pod weevil attack. Chapingo, 1955* (Grams per two row plot) Average Variety yield Reaction

Amarillo 156 (Commercial) 1.638 Resistant Amarillo 155 (Commercial) 1.601 !f EAP-88-B 1.425 II (Zac-4A-2 x Pue-32)-l 1.416 If (Hgo.l4A-3 x Pue-2)-l 1.575 n Amarillo 154 (Commercial) 1.556 it (Roc-1 x Pue-32)-l 1.551 it (Roc-1 x Pue-32)-l 1.252 Tf Roc-3 Check. (Commercial) 1.037 It Bayo 160 (Commercial) 1.027 Susceptible Pinto 162 (Commercial) 1.117 IT Regro 152 (Commercial) 0.851 It (Pue-32 x Roc-1)-l 0.778 11 Bayo crema 0.761 tl

Canario 101 (Commercial) 0.280 It -48-

Table 8.- Yield of bean lines and varieties under apion pod weevil attack, Chapingo. Mexico 1955 (Grams per one row plot)

Average Variety yield Reaction

(Hgo-38A-l x Pue-32-B2)-l .421 Resistant (Roc-1 x Pue-32-Dl)-l .585 11 (Hgo-6 x Hgo-14A-3-a-4)-l .368 tt (Roc-1 x Hgo-6-A-l)-l .565 11 (Canario x Hgo-15A-A-7)-l .525 n Amarillo 156 (Commercial) .503 ti Pue-32 x Roc-l-C2 .285 11 (Roc-1 x Hgo-6)-l .282 11 Pinto 162 (Commercial) .280 Susceptible (Roc-1 x Pue-32-D2)-l .276 Resistant Negro 150 (Commercial) .267 11 Bayo 160 (Commercial) .240 Susceptible (Pue-32 x Hgo-14A-3-l)-l .238 Resistant (Hgo-12A-l x Pue-32-E)-l .236 rr (Hgo-38A-l x Pue-32-A-l)-l .230 tv Bayo 164 (Commercial) .230 Susceptible (Pue-32 x Roc-1)-C4 .226 Resistant (Canario x Hgo-15A-A-6)-l .223 Susceptible (Roc-3 x Hgo-6-4)-l .203 Resistant (Roc-1 x Hgo-6-A-l)-l . 1 9 0 11 (Pue-32 x Roc-3-A-D-l .182 n Amarillo chico. .177 Susceptible Bayo 158 (Commercial) .156 11 (Roc-3 x Hgo-6-D-l)-l .101 11 Bayo rosa. .102 ti Bayo gordo (Commercial) .085 11 Negro viejo. .051 11 -49- Classification of Bean Varieties and Lines According to Resistance to the Apion Pod Weevil.

The system of classification of the "bean lines and varieties under study was based on the per cent of grains attacked because this measurement seems to be the best index of yield loss or reduction. Before setting the categories, the varieties were arranged in decreased order of insect attack. The range of variation in the Phaseolus vulgaris varieties was from 1 to 100 per cent attack. Prom 1 to 35 per cent, one variety varied from the other only by decimals of a per cent. Beyond 35 per cent there were progressively larger gaps in percentage of attack. Six categories were established, but only five appear in Table 9, because the immune varieties all belong to the species Phaseolus multiflorus. All varieties with more than 33 per cent of attacked grains are being discarded. Usually a cross between two resistant varieties pro­ duces more lines which carry the resistant character than a cross between a resistant and a susceptible variety. Crosses between resistant and low resistant varieties with good yield still have good chances of yielding several lines with insect resistance. Crosses with Canario, a very suscep­ tible variety only rarely produces a line carrying resist­ ance. Interspecific crosses with Phaseolus multiflorus seem not to produce a high degree of resistance. Table 9.- Classification of lines and varieties of beans according to resistance to the Apion pod weevil. Chapingo, Mexico. 195#.

Highly Low Highly resistant Resistant resistance Susceptible susceptible 1-8 % attack 3-15 % attack 15-25 % attack 25-35 % attack 35-100 % attack. c(Pue-lB3 x Hgo-l5A) Alemania blanca (Canario x Hgo-6 )A (Hgo-2i| x Roc-l)B c(Pue-lB3 x Hgo-l5A) (Hgo-6 x Hgo-lijA3)B (Hgo-6 x HgolijA3)D Canario x Hgo-l5A (Pue-2 x Canario )C (Canario x Pue-2 )A (Hgo-5 x Hgo-ll4A3 )C (Hgo-6 x Rpc-3 )C (Hgo-6 x Hgo-ll

Table 10.- Range of variation of apion pod weevil attack in interspecific crosses in beans. Filial Per cent of Cross seeds Generation______attacked ■

F-2 Canario x Hgo-15A ...... 98.00 F-4 (Canario x Hgo-15A-7)-2 ...... 17*64 F-4 (Canario x Hgo-15A-3)-l ...... 26.16 F-4 (Canario x Hgo-15A-4)-l ...... 7.14 F-3 Canario x Pue-1B3 x Hgo-15A ...... 8.00 F-4 Canario x Pue-1B3 x Hgo-15A ...... 32.00 F-3 Pue-1B3 x Hgo—15A ...... 58.00 F-4 (Hgo-38A-l x Hgo-15A-4)-l ...... 17.4-9 F-4 (Hgo-38A-l x Hgo-15A-4)-1 ...... 30.48 F-4 (Hgo-38A-l x Hgo-15A)-2 ...... 41.66 F-5 (Roc-1 x Hgo-15A-l)-l ...... 19.55 NOTES ON TEE BIOLOGY OF THE SEED COEN MAGGOT IN MEXICO.

The seed corn maggot, Hylemya cilicrura Rond, is known to attack many crops and wild plants. The most important hosts are beans, spinach, potatoes, cabbage, melons, peas and corn. This is one of the pests which is very often over­ looked by growers and even by entomologists due to the fact that the adults are inconspicuous in the field, and also because the larvae remain, in the case of beans, only about a week in the germinating seeds in the ground. When the plants emerge the larvae remain buried in the soil close to the primary roots. The adults are attracted by fresh manure in fields farmed with . They are also said to be at­ tracted to cultivated land especially when it is moist, (Reid 1940), Early in the Spring in the plantings of beans under irrigation for the early market, adults are except­ ionally abundant. They can be seen coming behind the planter in great numbers. When the beans are planted by hand many flies actually oviposit on the seeds or on the ground near­ by. Adults are very active early in the morning and in the late afternoon. They sometimes gather in swarms and hover at a height of 5 to 8 feet above the ground. The biological cycle of this pest was observed in Chapingo, Mexico, during the spring of 1955* to be as fol­ lows: incubation period about 3 days, larval period one week, pupation including prepupa, two weeks. The minimum -52- -53- life cycle in April was 24 days from egg to adult. Several adult diets have been studied with the purpose of increasing the number of eggs during oviposition, (Ristich and Schwardt 1949). An experiment was designed to determine the amount of oviposition by the flies at the moment of planting and in subsequent days. Several rows of Canario beans were planted by hand the second week of May. Immediately after covering the seeds with soil two half-cylinder shaped cages one foot wide and seven feet long were partially buried over two por­ tions of row selected at random. Each 24 hours two more cages were placed on different parts of planted rows. This procedure was continued for four days. The cages were lifted two weeks after the beans were planted and the germinated plants, as well as the ungerminated grains under the ground, were examined for seed corn maggot damage. The results of these observations are summarized in Table 11 and graphical­ ly represented in Fig. 4. Table 11.- Per cent of bean seeds and seedling damaged by the seed corn maggot after a few minutes to four days exposure to the adult flies. Chapingo, Mexico. 1955

Probable time 0/ for oviposition ^ insect damage

20 minutes 32.74 1 day 55.00 2 days 4-8.75 3 days 64.55 4 days 63.95 Per cent attack 0 - 30 10 - 70 40 - 40 20 60 50 - 50 - - Pig. 4.- Bate of Increase In per cent of cent per In Increase of Bate 4.- Pig. 0 Days seeds unprotected seeds Days after planting. after seed corn maggot attack on beans on attack maggot corn seed 1 2 -55

There was about 32 per cent damage done by larvae of seed corn maggot when the adults had a chance to oviposit for a few minutes before covering the seeds. This is half of the total per cent attack. However, it is doubtful that any seed color preference exists in adult flies. The only instance of a possible relation of color with oviposition response would be for this limited period of time. The damage done by this pest is illustrated in Fig. 5 and an example of recuperation of attacked plants is shown in Fig. 6. Bean seedlings damaged by H. clllcrura (Bend) Fig. 6.- Single bean plant on the right reouperated after IL* c HI crura (Bond) damage. -59-

Experiment on Seed Color Preference by Hylemya cilicrura.

During May 1955* an experiment was designed to test a small group of varieties of different seed coat colors. A larger group would have been more desirable, but would have involved much labor digging up every plot to examine .each plant for insect damage. Twelve varieties were selected, two of each color shown in Table 12, and planted in plots of four rows 18 feet long in a modified 6 x 6 latin square design. Two weeks after planting, the plants were dug up and carefully separated into attacked and undamaged groups determining from these the per cent of attack. The percent- p age values were transformed to "sen 9" using Hayes & Immer

(1942) tables. The statistical analysis was based on these values and appears in Table 12.

As was mentioned before, perhaps seed color has no influence on adult flies preference directly, but might be associated with minute differences in odor which atract the tiny larvae or the adult to a particular variety. -60-

Table 12.- Average per cent of seed corn maggot damage on different bean varieties grouped by colors.

Percent Group Variety insect attack

A Brilliant black 26.283 * a Black opaque 24-. 633 * A Dark brown pinto 26.535 * a Black scarlet runner 28.866 * A Brilliant yellow 30.266 * a Opaque yellow 30.366 A White scarlet runner 51.555 a Black pinto 32.955 A Canario (tan) 31*833 a Alubia (white) 52.953 A Bayo bola (tan) 36.500 a Opaque tan 33.333

* L.S.D. .05% for group "A" 5*4-55 L.S.D. .05% for group "a” 4.034

A- Brilliant colors, a- dull colors. -61- The evidence in this experiment points out that at least the black colored beans are less preferred by the seed corn maggot larvae in the soil.

Preliminary Selection of Varieties Resistant to the Seed Corn Maggot.

Additional information was obtained in the resistance of beans to the seed corn maggot in Columbus, Ohio in 1956 while studying the resistance of 250 varieties of beans to potato leafhopper. Grading the varieties for seed corn maggot resistance was based on percentage of undamaged or normal germination. Determination of infestation by removal of plants was im­ possible because all the plants had to be saved for later leafhopper studies. This method is relatively inaccurate because a few seeds do not germinate due to seed decay and some of the seedlings which were attacked under the ground may germinate and present the appearance showed in Pig. 5» This type of damage may be confused in some instances with "baldhead" damage caused by mechanical injury during tresh- ing. Also there are differences in germination in varieties due to other causes. To minimize insofar as possible the influence of some of these factors in determining insect attack, certain portions of rows with no germination were dug to ascertain whether or not the fly larvae were destroy­ ing the plumulae of the seeds. An average of six pupa or -62- larvae of the seed corn maggot per foot or row was found in the varieties with poor germination. The group of varieties most susceptible to the seed corn maggot came from the Southeastern Vegetable Breeding Laboratory at Charleston, S.C. Out of 102 varieties only 15 had above 80 per cent germination, the rest had low germina­ tion and heavy insect damage. In the Table 15* there follows a list of what may be considered varieties resistant to H. cilicrura during 1956 in Columbus, Ohio.

Table 13.- Bean varieties from Charleston, S. C. resistant to H. cilicrura in Columbus, Ohio. 1956 (more than §6% undamaged germinated plants)

Asgrow black valentine. Cherokee wax. Contender. Fulgreen. Stringless black valentine. B-1625-17-2-1-3. Glades. B-2957-1. Wax-R15. Tendergreen. B-2935-1-1-3. B-3035-1-1-1. B-2972-1R.

Some of the seeds received from different seed compa­ nies were treated with insecticides and no comparable notes could be taken in these varieties. However, out of 43 un­ treated varieties those listed in Table 14 were the least infested. Table 14-.- Bean varieties from various companies resistant to H. cilicrura. Columbus, Ohio. 1955*

Tendergreen 6162 (B) Improved tendergreen (K) Stringless black valentine (B) Sulphur 5179 (K) Bountiful 6162 (B) Black valentine stringless A-224- (K) Pencil pod wax 6176 (B) Slendergreen 52376 (R) Longreen 5091 (B) Improved tendergreen Round pod kidney wax 7233C (PH) 52339 (H) Red valentine stringless Tendergreen improved 0-617.6C (PH) 82632 (PM) Dwarf horticultural 4-6908C (PH)

Most of the 63 Mexican varieties tested were very re­ sistant, only three varieties were slightly susceptible. PRELIMINARY EXPERIMENTS ON THE SELECTION OP BEAN VARIETIES RESISTANT TO THE POTATO LEAFHOPPER

The potato leafhopper, Empoasca fabae(Harris) shown in Pig. 7 belongs to the Cicadellidae, a very large and eco­ nomically important family of phytophagous insects. Oman (194-9) lists 177 North American species of the Empoasca. Prom Mexico, 61 species of the same genus are re­ ported, 51 of them are in the collection of Dr. D.M. DeLong at Ohio State University and are described by him as author or coauthor in various papers. Recently Gonzalez (1955) described seven Empoasca species, four of them attacking beans in Mexico. Out of this great number of species at least seventeen are of economic importance. Many species of this genus are difficult or impossible to separate on ex­ ternal characters. However, DeLong in 1931 demonstrated that they can be identified by examination of internal male genitalia. The biology of the potato leafhopper on beans was throughly studied by DeLong (1938). He also reported the distribution of Empoasca fabae in the United States and concluded that E. fabae is generally an important pest east of the 100th meridian on the eastern half of the United States. In Mexico Gonzalez (1955) made population studies of E, fabae and found that this species occurs in the north­ eastern, central and southern portions of the country. He includes a list of host plants for this species, listing eleven plant families, increasing the already extensive list -64- reported "by Poos and Vdieeler (194-3, 194-9). In connection with this subject of host plants, Oman is of the opinion that economically the most important species of leafhoppers are those that have a wide variety of hosts. Pig* 7*- The potato leafho- per, Emnoasoa fabae Harr* Tnatural size 4 mm*) -67- Experiments at the University Farm, Columbus, Ohio,

On June 7* 1956, 240 varieties of beans were planted and on June 27 a second planting of the same varieties, plus ten more varieties which arrived later, was made. The source of these varieties was as follows: 102 varieties supplied by the Southeastern Vegetable Laboratory, Charleston, S.C., 61 provided by different seed companies in the United States, 6J sent by the Agricultural Branch of the Rockefeller Foun­ dation in Mexico and 25 varieties furnished by the Agricul­ tural Branch of the Rockefeller Foundation in Colombia, S.A, Almost all the varieties from the United States that were planted were of the snap-bean type, the varieties from Me­ xico and Colombia of the types utilized as dried beans. Many Mexican and Colombian varieties were not adapted to Columbus conditions, but among bhe Mexican varieties there were several that showed very good adaptation, earliness and good yields.

Experimental Designs.

Due to the large number of varieties employed, the ex­ periment was designed with just two replications; as was mentioned above, the same varieties were planted twice 20 days apart. More than a replication, this second planting may be properly named a duplication, because it was carried on under different weather conditions, under a lower level -68- of leafhoppers and used treated seeds instead of nontreated seeds as in the first planting. Variety numbers were randomized in each planting and planted in single rows 10.5 feet long, separated by alleys 2.5 feet wide. Thinning after germination left approximate­ ly the same number of plants per row. When the plants bore the second trifoliate leaf, half of each row was treated with approximately 1/2 pound of active methoxychlor per acre in wettable powder sprays using a knapsack sprayer; subsequent sprays were made at 9 day intervals, using double the above amount of methoxychlor. The first planting date received two sprays and the second planting four sprays, this last number of sprays is the program regularly applied to beans on the University Parm.

Relationship Between the Potato Leafhopper and Bean Plants.

The potato leafhopper was already present in the field by June 15 when the first planting began germinating. Al­ though in very small numbers, the insects started feeding and ovipositing. The damage at the begining of the season was not very pronounced. The first nymphs were observed five days after the beans germinated, most of the damage being done by adults. The first treatment with methoxychlor was applied 10 days after germination on half of each row. Just 6 days later the differences between the treated and untreated portion of each variety was quite noticiable on -69- the susceptible varieties.

Leafhopper Damage.

The type of damage done by the potato leafhopper has been described very extensively by DeLong (1958) on po­ tatoes, beans, alfalfa, rhubarb, apple, etc. On beans the typical damage is characterized by curling or rolling, ac­ companied by crinkling and roughening of the leaf. Dwarf­ ing of the leaves and stunting of the plants is of common occurrence. Yellowing and bronzing and finally weakening of the plant usually are the more advanced symptoms. In the experiments described herein there occurred an oppor­ tunity to observe the reaction of different bean varieties to this species, because each variety had an untreated check and a treated portion in the same row. Most of the varieties in the first planting had some yellowing of the primary leaves. However, a group of varieties presented characteristic rolling symptoms. This group is listed in Table 15 and these symptoms are illustrated in Fig. 8. Initial stunting and dwarfing of the leaves was somewhat variable. On the second planting this was almost exclu­ sively the type of damage observed. There are two types of stunting in relation to the damage caused by Empoasca fabae on beans. The more commonly observed results from the heavy attack by adults and nymphs, the other type is easily con­ fused with healthy plants if treated plants of the same -70- variety are not growing in the same or adjacent rows. This is true because there is no curling, rolling or yellowing, the plants just have fewer and smaller leaves and also are smaller in size than normal. This damage was observed when many adults were feeding and ovipositing and very few small nymphs were present. Fig. 10 shows this insect damage in the untreated part of a variety, which corresponds to the stunt­ ed portion of the row. -71-

Table 15*- Bean varieties with rolled type of symptoms caused ty the potato leafhopper.

Variety Source of supply

Davis stringless wax BC 1-6634- F.H. Woodruff Seed Co Red val. stringless 0-61760 B-2528-2-1 Charleston, S. 0 B-2523-2-1-2 B-3093-1 Green pod bush 551132 1851-9 Chevert stringless Stringless black valentine Var. 11-11-R1-14-20-2-3-u Mexico. Var. 16-11-17-62-1-ux-u Mexico. -72- Recuperation of the Bean Plant from Insect Attack and Seasonal Differences.

There were not very many varieties which exhibited a marked capacity for recuperation from the attack of E. fabae. Only 3% of the bush varieties showed recuperation. Eighteen percent of the late pole non-adapted varieties also recu­ perated from the attack of leafhoppers. The name of varieties which had recuperative ability after attack by the potato leafhopper are shown in Table 16.

Table 16.- List of varieties with recuperative capacity after the attack by E. fabae. Columbus, Ohio, 19567

Amarillo 154** Tennessee green pod 06187 (FH) Amarillo 155. B-1625-17-2-1-3 (CH) Bayo 159. B-2637-1-1 (CH) Bayo 160. Bayo 164-. Jalisco 117* Puebla 125. 18-11-3-692-1-1-u (bush)

Another type of recuperation was exhibited which may be termed very early recuperation that was observed in a few varieties. One of the examples of this phenomenon is illustrated in Pigs. 8 and 9, where a comparison is made of the same variety two weeks after heavy rolling was observed. -73-

Pig. 8.- Symptoms of leafhopper attack on (M) variety of beans showing characteristic leaf rolling. Pig. 9V- Recuperation from leaf-roll type of damage on U-II-R1-l4-20-2-3-u (M) variety of beans. • 10.- Stunt type or damage on untreated portion of sub- ceptible variety (Tendergreen Improved. 82639. P.M.) -76- The reaction of different varieties varies with, the season and insect population density. The type of damage observed in the planting of June 7 was somewhat different from that observed in the planting made 20 days later. There was a yellowing and curling of leaves in the first planting and only a generalized stunting of plants in the second planting. The amount of damage noticed in a variety and the effect of this on the yields may vary with environ­ mental factors but it seems that the inheritance of a par­ ticular variety is very important in this respect. Some varieties withstand more damage than others without being affected in yield. Examples of this last group are the va­ rieties Hyscore and B-2523-2-1-2 from Southeastern Vegeta­ ble Breeding Laboratory in Charleston, S,C. and a few others.

Effect of weather on the Potato Leafhopper and the Bean Plant.

As stated by DeLong (1938), normal precipitation in the eastern states is favorable for the developing of high populations of Empoasca fabae. Very heavy, wind-blown rain has a detrimental effect on this species. Also the distri­ bution of this pest in the United States is very much cor­ related with altitude, temperature and rainfall. In Mexico there has been no study on the ecology and distribution of this insect but it is reported as an important pest in the -77- high. valleys from 5600 to 7800 feet above sea level in the spring and at lower elevations in areas without frost (1500- 3000 teet) in the winter. Although the leafhopper population may not be much disturbed by rains, the bean plants benefit so much that by putting on great amounts of foliage in a short time there is a rapid recovery in many varieties when the infestation is not to great. Wilson and Davis (1955) have observed the same condition in alfalfa. Leafhoppersdamaged most of the plots receiving less than normal irrigation. One factor that undoubtedly contributed to a reduction of the total population of leafhoppers in test plots was the treatment of the beans in adjacent fields at the Univer­ sity Farm with insecticides and especially the insecticidal treatment of half of each row of every variety in the present experiments. However, the inclusion of a treated check in each variety was extremely useful in observing the difer- ences in vegetative growth as well as the typical leafhopper damage. Also this system helps in distinguishing the damage done by leafhoppers from that caused by virus diseases.

Tolerance of Different Bean Varieties to the Potato Leafhopper.

It is extremely difficult to evaluate the leafhopper population in a large number of varieties of beans with small plots. Even in larger plots the counts of adults are not completely reliable. DeLong (1932) has discussed the prob­ lems involved in obtaining counts of Empoasca. Perhaps the most important of these problems is the more or less regular movement of the adults from plant to plant particularly when disturbed. Therefore, counts in susceptible and tolerant varieties were based on the number of nymphs present. None the less considerable damage was caused by the adults. Only those varieties growing in adjacent rows were chosen for comparison. Whenever a pair consisting of a susceptible and tolerant variety occurred together the nymph population was counted on five trifoliate leaves of five plants chosen randomly in each variety. The counts were made at blossom time. The results of these counts are tabulated in Table 17 and represented graphically in Pig, 11. -79-

Table 17.- Population of nymphs of the potato leaf­ hopper on 25 trifoliate bean leaves of suscep­ tible and tolerant varieties grown in ad­ jacent rows. Columbus, Ohio. 1956.

Susceptible Resistant

VARIETIES PLANTED JUNE 7. a 158-1-14-3-2-M-M. 115 b Cherokee wax. 107 c Zac-51• 147 d Wade 4244. 73 e Jal-117. 185 f Hgo-63-l-u. 79 g Qro-24. 115 h Eulgreen x Tendergreen. 77 i Stringless B. val. 105 a B-3078-1. 125 k Bayo 164. 96 1 Imp. Tendergreen 5221. 92 VARIETIES PLANTED JUNE 27. m 7-II-R,-14-20-l-2-u. 12 n Logan 1-7239. 10 0 B-2523-2-1-2. 10 p Eulgreen x Tendergreen 8 q. B-2761-X. 12 r Perry's Plentiful 79888 16 s Tenderlong 15-584. 14 t B-1625-17-2-1-3 12 u Burpee's S.Green pod v B-3076-3 12 6163. 14 x Processor 5109 18 w Landreth's S.G. pod X8317- 20 -80- The difference in number of nymphs on susceptible and resistant varieties does not seem great enough to indicate a particular preference in the varieties observed, except in Zacatecas-51 and Jalisco-117* Therefore, so far as these tests are concerned, most of the varieties show resistance through the mechanism of tolerance« The varieties classi­ fied as resistant do not show any reduction in growth and yield as compared with the check, in spite of supporting approximately the same nymph population as the susceptible ones •

/ Inseots per 25 trifoliate leaves 150 - 150 100 50 # Varieties listed in 17.listed Table # Varieties # a b c d d c b # a Fig. I Varieties planted June 7* June planted Varieties 11.- I Nymphal population of E. fabae on susceptibleon of fabae resistantE.population and Nymphal bean I e 4 g 1 k 1 k J 1 h g f varieties growing in rows.adjacent varieties growing

o n n Varieties planted planted 27.JuneVarieties pqrstuvwx

H 00 1 1

-82- Cause of Resistance of Beans to Leafhoppers.

The matter of tolerance of the bean plants to potato leafhopper attack will perhaps be hard, to explain without a biochemical analysis of the sap and a physical comparison of the damage done by the insects to phloem and xylem tis­ sues. There are several theories advanced to explain the causes of "hopperburn" and crinkling of the leaves. Fenton and Hartzel (1925) and Eyer (1922) believe there is a specific toxin which is injected into the plant, causing the apparently disease condition. Smith and Poos (1951) and Smith (1953) studied the damage done by E. fabae to conduc­ tive tissues. Their observations show that there is a plugging of the xylem tubes in certain portions of the mid­ ribs and stems. This disruption appears to produce a delay in translocation or interference with the normal function of the phloem, plugging results in distorted shape and is thought to be produced by the punctures of the proboscis and ovipositor. Two interesting studies that delve into the biochemistry of the plant in relation to piercing-sucking insects are those of Johnsen (193^) who proposes the hypo­ thesis of carbohydrate accumulation and reddening of tissues of legumes and potatoes. Whatever the cause of resistance may be, it is possible by employing treated check plots to pick out resistant and susceptible bean varieties even under low infestation of leafhoppers. Pubescence has been reported as being associated with resistance of legumes to the potato leafhopper; instances of this type of resistance are in the reports of Pieters (1928) concerning red clover, Hallowell and Johnson (1934-) on soybeans and Poos and Smith (1931) on stringless green pod bean. However, Granovsky (1928) and Jewett (1929) found that hairy Peruvian alfalfa was attacked in a manner similar to other alfalfas. Taylor (1956) states that fac­ tors other than pubescence have an important function in increasing resistance to leafhopper injury. He bases his concepts on an evaluation of pubescence as a source of leafhopper resistance in alfalfa varieties by determining its mode of inheritance. He also investigated the relation of pubescence to leafhopper resistance. Pubescence was in­ herited as a quantitative character, although there is a correlation between pubescence and resistance and this is inherited. However, there is considerable variation and in some of the crosses the glabrous parents were classified as resistance. In observations made in 194-9 on 98 different lines and varieties of soybeans the range of damage was from zero to 80 per cent. However, there were resistant varieties of both glabrous and pubescent types. Among the 250 varieties of common beans tested in the present study there was one variety which was very prominent because of its hairiness but it was also one of the most susceptible varieties to -84- Empoasca fabae. This variety is shown in the foreground of Fig. 12. In view of these observations I am inclined to be­ lieve that the matter of resistance in beans to Empoasca fabae seems more complicated than the simple possession of pubescence.

Method of Estimating Resistance and Susceptibility of Bean Varieties to the Potato Leafhopper,

Grading leafhopper damage was accomplished by making two readings about one month apart in each of the planting dates. Degree of insect damage was determined according to the following scale. 0 = No damage. 1 = Slight damage (little stunting and curling). 2 = Medium damage (stunting, curling or rolling and yellowing). 3 = Heavy damage (symptoms same as 2, plus foliage in check at least double the size in untreated row ). Resistant varieties in this work are considered to be only those which show zero damage in both planting dates, June 7, and June 27. This does not mean that these varietes were not attacked; the infestation of nymphs in all the va­ rieties was about the same, as was shown in Table 17* • 12,- Var 138-1-1^-3-2-M-M a pubescent susceptible variety from Colombia, S. A I

-86- Varieties of low resistance are listed as those having the grades 0 & 1 and 1 & 1. Susceptible varieties are con­ sidered here to be those having the grades 1 & 2 and 2 & 0. Highly susceptible varieties, so far as this work is con­ cerned, include those with grades 2&2, 3 & 1, 3 & 2 and 3 & 3.

Results in Resistance to Leafhopper Attack.

Yields of most of the green bean varieties were re­ corded in order to check the influence of degree of damage on yield. Because only two replicates were run due to the large number of varieties tested, yield data was not ana­ lyzed statistically. However, in a great many cases heavy damage lowered the yield of the varieties affected, often resulting in half or less the regular yield obtained in the treated check. In Table 18, there is presented a comparison of yields and groupings of some of the varieties tested. Resistant varieties, as was pointed out before, do not show appreciable difference in the yield of the treated and untreated plants. Table 19 contains the varieties free of damage and therefore resistant to Empoasca fabae. -87-

Table 18.- Comparison of total yield (in pounds per plot) of different varieties in relation to resistance to Empoasca fabae. Difference Variety Tr^ e4 Untreat ' between row the plots. Kinghorn special 0.758CL (EH) 6.72 3.62 3.10 Highly susc B-1788-21-1 (CH) 6.12 3.32 2.80 11 n B-3096-1-1 (CH)! 7.05 5.57 2.30 11 n Tendergreen imp. 82632 (EM) 5.80 3.72 2.08 11 11 B-2934-1-1-1 (CH) 5.05 3.20 1.78 IT II B-3119-3 (CH) 5.40 4.00 1.40 Susceptible White seeded tendergreen 0-7319CD (FH) 4.97 3.80 1.17 ft Full measure 46894C (EH/) 4.10 3.10 1.10 Ff Imp. tendergreen 5221 (K) 4.17 3.30 0.87 H Giant stringless 4136 (K) 3.47 2.50 0.97 If Topmost (CH) 4.52 3.67 0.75 Low resist. Red valentine stringless 0-6176C (FH) 5.00 4.25 0.75 11 11 B-2948-2-1-2 (CH) 4.57 3.82 0.75 11 it White seeded tendergreen (CE) 3.57 3.00 0.57 11 11 Woodruff's hyscore 0-7360CD (FH) 4.85 4.25 0.60 11 n B-2932 (CH) 3.75 4.40 •-0.65 Resistant. Eullgreen x Tendergreen (CH) 4.90 3.50 ■-0.60 it B-2446-1-6-1-3 (CH) 4.12 5.25 ■-0.12 11 Pearlgreen (CH) 4.65 4.40 0.25 it B-2920-2 (CH) 3.45 3.15 0.30 n Table 19.- Resistant varieties to the potato leaf­ hopper in Columbus, Ohio. 1956.

Fulgreen x Tendergreen (CH) B-2194-1-1 (CH) Contender (CH) Pearlgreen (CH) B-2920-2 (CH) B-2446-1-6-1-3 (CH) B-3033-7-2 (CH) Top Crop 10532 (K) B-2952 (CH) Seminole 5170 (K) -89-

Table 20.- Bean varieties of low resistant to the potato leafhopper. Columbus, Ohio. 1956

B-2528-$r-l (CH) Asgrow black valentine (CH) Florida belle (OH) B-2957-1 (CH) Glades (CH) B-2968-2-1 (CH) B-2567-1 (CH) U. S. 5 (CH) Tendergreen (CH) B-2748 (CH) Green pod bush 551132 (CH) Bountiful 6162 (B) B-2449-CB (CH) Rustproof golden wax 5094- (B) 1831-9 (CH) Longreen 5091 (B) B-3092-2 (GH) Top crop 5084 (B) B-3054-2-1-1 (CH) Plentiful 6802 (B) Wade (CH) Tendergreen 6162 (B) Topmost (CH) Burpee's brittle wax 6171 (B) B-2950-1-4 (CH) Improved tendergreen (R) Top crop (CH) Slendergr.een (R) B-2950-1 (CH) II-R.-14-20-2-1-u (M) Copper wax (CH) Canario 101 (M) B-3110-X (CH) 16-11-17-62-1-ux-h (M) B-370-CB-1X (CH) Qro-17 (M) 101W (CH) 11-II-12-62-U (M) Fullgreen 2 (CH) Zac-61-l-xu (M) B-3076 (CH) Dark red kidney 82639 (FM) Seminole (CH) Processor'5109 (FM) B-3095-3 (CH) Dwarf horticultural 46908C (FH) Cherokee wax (CH) Supergreen BC1-7526 (FH) B-294-8-2-1-2 (CH) Giant s. green pod 0-7896 (FH) B-3088-2-3 (CH) Red val.stringless 0-6176C (FH) B-3076-3 (CH) Idaho refugee 0-2237C (FH) White seeded tendergreen (CH) Kingreen 448780 (FH) Green pod bush 551131 (CH) Woodruff's hyscore 0-7360CD(FH) Plentiful (CH) Wade 4244 (K) B-3035-1-1-1 (CH) Contender 5121 (K) Wax H-15 (CH) Sulphur 5179 (K) B-3078-1 (CH) Japon (C) The remaining 174 varieties not included in these ta­ bles were graded susceptible or highly susceptible. Eon- adapted varieties appeared rather susceptible. This does not mean that all non-adapted varieties are non-tolerant, Among the Mexican and Colombian non-adapted varieties ob­ served there was one resistant, four low resistant, seven susceptible and 25 highly susceptible varieties. In Figs. 13, 14 and 15 three illustrations of va­ rieties resistant to the potato leafhopper are shown. Highly susceptible varieties exhibited striking difference in growth or damage symptoms in treated and untreated por­ tions of the row. 1 3 .- A leafhopper resistant variety Contender (CH) Pig. 14.- Variety Bountiful 6162 (B), resistant to leaf-hopper attack. Pig. 15.- Leafhopper resistant variety Glades (CH). DISCUSSION

The present discussion will be limited, to stressing a few major points already mentioned throughout the text of this paper. To date studies at the Experiment Station at Chapingo, Mexico, on varieties resistant to insects have been restricted to beans. A large portion of the bean crop in Mexico is planted on small plots for’ family use. Very often these beans are planted in association with corn due to the limited available agricultural land and water for irrigation. This system makes it very difficult and ex­ pensive to treat the plants with insecticides. It is be­ lieved that the problem of insect damage to beans will best be solved by the use of resistant varieties. It was demonstrated in yield test comparisons between resistant varieties and improved commercial varieties re­ leased by the Experiment Station that some varieties sus­ ceptible to the apion pod weevil have already been dis­ tributed to the farmers. However, a few varieties which were released are resistant. These varieties were selected unconsciously because the selections were made on the basis of agronomic characters from plots protected with insecti­ cides . Insect population density seems to be important in selecting resistant bean varieties. In Mexico it was ob­ served that very heavy population of apion pod weevils late in the season caused 100 per cent damage in the susceptible

-94- -95- varieties and considerable damage even in the resistant ones. The tolerance of the bean varieties to the potato leafhopper also varies with the number of insects present. Insect biotypes of a particular species are undoubt­ edly in existance in the same or different regions. Also some insect species change their preferences for food. However, only a few insect biotypes have been reported and most of the cases of insects that have changed their food preference are known only from the laboratory. In any event, this problem definitely exists. It is worthy of considera­ tion to try in insect resistant work a program similar to that employed by plant pathologists, and the avoidance of rather uniform distribution of pure lines. This method is described under the subject of insect outbreaks, which essentially consists of the creation of ',composite"varieties. These varieties have been produced by crossing well adapted commercial varieties with a group of varieties carrying dif­ ferent types of resistance. Each single cross is backcrossed several times to the commercial variety. The variety as dis­ tributed to the farmers is a mechanical mixture of lines which are similar in appearance but carry different sources of resistance. It seems that the knowledge we have about tolerance of plants to insect pests is very superficial. Most of the data gathered on the subject comes from observations on re­ sistant varieties planted in one season. To be able to in- -96- vestigate more about the tolerance it will he necessary to plant a group of tolerant varieties in an experiment of planting dates for more than one season and also to carry a series of tests on greenhouse under more controlled condi­ tions, especially on nutrients and soil moisture. It was thought that the interspecific crosses between the scarlet runner, Phaseolus multiflorus. which is immune to attack by the apion pod weevil, and the common beans, should be resistant to the insect pest; some segregates however, which had characteristics of both parents were generally rather susceptible and only those plants which, were completely similar to the scarlet runner type had im­ munity. This species of beans is not commercially accepta­ ble, therefore, the crossing program should be directed in the future toward breeding with resistant and good yielding varieties from the common bean type. SUMMARY

The apion pod weevil, Apion godmani Wagner, is an im­ portant pest of beans in Mexico. It usually occurs in the central plains and high valleys. It does not occur in the northern plains bordering the United States. The weevils are a pest in the field, attacking the young seeds in the pods. A group of resistant varieties were selected from approximately 500 varieties. Most of the resistant varie­ ties, except Rocamex-1, Hidalgo 12-A-l, Puebla-2, and EAP-

88B had had little commercial value. No correlation was found between morphological characteristics of the plants, pH of the pods, rust resistance and the resistance of bean plants to the insects.

A total of 371 crosses were made between resistant va­ rieties and commercially adapted varieties. Selections made in the F-4 and F-5 generations were tested in yield trials using the parent and other commercial varieties as checks.

The results indicate that many crosses outyield the commer­ cial varieties. Also in these tests it was found that sev­ eral varieties distributed to the farmers by the Experiment

Station in the past are rather susceptible to A. godmani since they were selected under the protection of insecti­ cides .

In preliminary studies of the resistance of bean varie­ ties to seed corn maggot, Hylemya cilicrura Rond, in 1955

-97- -98- correlation between color of grains and resistance of va­ rieties to the insects was found. A decreasing order of re­ sistance was found in 12 varieties, two of each color as follows; black, pinto, yellow, white and tan. Color itself may not be important in the insect preference but perhaps could be associated with certain odors. In 1956 a group of resistant varieties were selected which had appreciable re­ sistance to E. cilicrura. An experiment with 250 varieties was conducted in Columbus, Ohio during 1956, to select beans resistant to the potato leafhopper, Empoasca fabae(Harris) Among the varieties selected in 1956 which were most tolerant to attack by leafhoppers were: Eulgreen x Tender- green (CH), Contender (CH), B-2920-2 (CH), 33-3035-7-2 (CH), 33-2952 (CH), B-2194— 1-1 (CH), Pearlgreen (CH), B-2446-1-6- 1-5 (CH), Top crop 10552 (K) and Seminole 5170 (K). GLOSSARY OF ABREVIATIOHS b ...... Black. c...... Canario. Diff..... Difference. G ...... Green. Hgo- Hidalgo. Imp...... Improved. L.S.D.... Least significant difference. Mex- Mexico. Pue- Puebla. Resist... Resistant. Roc- Rocamex. S ...... Stringless. Suscep... Susceptible. Tlax Tlaxcala. Tend Tendergreen. Treat.... Treated. Untreat.. Untreated. Y a ...... Valentine. Var. Variety. Zac-..... Zacatecas, (A)..... Asgrow Seed Co. (B}..... Burpee Seed Co. (C)..... Colombia. (CH) Southeastern Vegetable Breeding Laboratory. Charleston, S.C. (FH) F. H. Woodruff Seed Co. (FM) Ferry Morse Seed Co. (K)..... Corneli Keystone Seeds, (M)..... Mexico. (R)..... Rogers Bros. Seed Co.

-99- REFERENCES CITED

Allee, W.C., 0. Park, A.E. Emerson, T. Park and K.D. Schmidt, 194-9# Principles of ecology. W.B. Sauders Co., Philadelphia, P-709. Ananthakrishnan, T.N., 1955# Host preferences in Retithrips syriacus (Mayet). Agric. Univ. Jour. Res. Sc. (India; 4(1): 283-88., B.A. 29: 22552. Anon. 194-0. Resistance of lima beans to Empoasca. Rpt. Puerto Rico Exp. Sta. 1939: 59^62. TITXif.""29: 4-69-4-73). Arant, F.S. and M. Jones, 1951* Influence of lime and ni­ trogenous fertilizers on the population of green bug infesting oats. Jour, Econ. Ent. 4-4-: 121-22. Arenz, B., 1951. Further results on the resistance of the potato to Myzus persicae. Z. Pflanzenb Pflanzenschutz 2: 63-67 (P.B.A. 21: 2S04--05). Ballard, W.W., 1951* Varietal differences in susceptibility to thrips injury in upland cotton. Agron. Jour. 4-3: 37-44. Barker, J.S. and O.E. Jamber, 1951. Fecundity and plant in­ jury of the pea aphid as influenced by nutritional changes in the garden pea. Jour, Econ. Ent. 44: 1010- 1012. Beard, R.L., 1951. The susceptibility of maize to the corn leaf aphid. Jour. Econ. Ent. 44: 1024-25. Beck, S.D., L. Haseman and R.H, Painter, 1951. Physiolog­ ical relationships of plants and insects. Abs. Amer. Assoc. Econ. Ent. North Cent. States Br. Proc. 6: 58- 61. Bennett, W.H., 1954-. The dffect of needle structure upon the susceptibility of hosts to the pine leaf miner. (Exotelia pinifolia Cham.) : Gelechidae. Canad. Ent. 8 6 : 49-54. (R.A.E. 43: 352). Beyer, A.H., 1922. The bean leafhopper and hopperburn with methods of control. Fla. Agr. Expt. Sta. Bui, 164: .61-88.

Bobinskaia, S.G., 1953. The meaning of the mineral nutrition of plants in the development of the cabbage aphid (Brevicoryne brassicae) (In Russian). Ent. Obozrenie 3 jrw-wfrtb’;xt'ss r*47o). -100- -101- Borlaug, H.E., 1953. Hew approach to the breeding of wheat varieties resistant to Puccinia graminis tritici. Abs. Phytopathology 43: 467. Brues, C.T., 1952. How insects choose their food plants. U.S.D.A, Ybk: 37-42. Callaham, R.Z., 1954. Comments on "Is host condition the cause of insect outbreaks?" Jour. Eoresty 52: 451-52. Callenback, J.A., 1951. Roscue wheat and its resistance to wheat stem sawfly attack. Jour. Econ. Ent. 44: 999- 1001. Cartier, J.J. and R.H. Painter, 1956. Differential reactions of two biotypes of the corn leaf aphid to resistant and susceptible varieties, hybrids and selections of sorghums. Jour. Econ. Ent. 49: 498-508. Cattier, W., 1948. Resistance of dwarf beans to field in­ festation by bean weevil (Bruchus obtectus Say) Hew Zealand. Jour. Sci. and Tech. 29A (6): 284-86. Coons, G.H. , 1953. Breeding for resistance to diseases. U.S.D.A. Ybk: 174-92. De Leon, D., 1954-. Is host condition the cause of insect outbreaks? Jour. Eoresty 52: 202, DeLong, D.M., 1932. Some problems in the estimation of in­ sect populations by the sweeping method. Ann. Ent. Soc. Amer. 25: 13-17* 1938. Biological studies on the leafhopper Empoasca fabae as a bean pest. U.S.D.A. Tech. Bull. Ho. 618. Dethier, V.G., 1951. Host plant perception in phytophagous insects. Internatl, Cong. Ent. Trans. IXth (2): 81-89. 1954-* Evolution of feeding preferences in phytophagous insects. Evolution 8: 33-54-* Dharmarajulu, K., A.G. Sechadri, M.V. Ramaswami and R. Balasubrahmanyan, 1948. Studies on host resistant of cotton to stem weevil. (Pempherulus affinis).(P.B.A. 21: 1194. Eden, W.G., 1952. Effects of kernel characteristics and components of husk cover on rice weevil damage to corn. Jour. Econ. Ent. 45: 1084-85. -102- Emery, W.T., 1946, Temporary immunity in alfalfa ordinarily susceptible to attack by the pea aphid. Jour. Agr. Res. 73: 33-43. English, L.L., 1955« The need for common sense in the con­ trol of insect pest. Jour, Econ, Ent. 48: 279-282. Eyer, J.R., 1922. Notes on the etiology and specificity of the potato tip burn produced by Empoasca mali Le Baron. Phytopathology 12: 181-84.

Barstad, C.W., 1951* Influence of wheat varieties on the wheat stem sawfly,'cephus cinctus. Internatl. Congr. Ent. Trans. IXth (1): 28^-88 (B.A. 28: 29780).

Eennah, R.G., 1931* Some aspects of the food problem of homoptera in the humid areas of the neotropical region. Internatl. Congr. Ent. Trans. IXth (1): 260-65. Benton, F, and A. Hartzell, 1923, Bionomics and control of the potato leafhopper Empoasca mali Le Baron. Jour. Econ. Ent. 13: 400-408.

Fraenkel, G., 1951. The nutritional value of green plants for insects, Internatl. Cong. Ent, Trans. IXth (2): 90-100. Franz J,, 1949. (On the genetic reason for the collapse of an outbreak from internal causes). Z. Angew Ent, 31 (2): 228-260 (R.A.E. 40: 16).

Gallun, R.L., 1955. Races of hessian fly. Jour. Econ. Ent. 48: 608-9. Glen, R., 1954. Factors that affect insect abundance. Jour. Econ. Ent. 47: 398-405.

Gonzalez, G.A., 1955. Ciclo biologico y control de las chicharritas del genero Empoasca, en cultivos de fri- jol en Mexico. Univ. Nal, Aut. 5e Mex. Tesis. 1955» Graham, S.A.., 1951. Developing forest resistant to insect injury. Sci. Mo. 73: 235-44. Gravnovsky, A,A., 1928, Alfalfa "Yellow top" and leafhoppers. Jour. Econ. Ent. 21: 261-66. Grison, P.A,, 1952. Relations between the physiological state of Solanum tuberosum and the fecundity of the Colorado potato' beetle Leptinotarsa decimlineata Say. Internatl. Congr. Ent. Trans. IXth, Tl): 331-3'/'. -103- Guevara, C.J., 194-9. New chlorinated nitroparaffin insecti­ cides against the potato leafhopper (Empoasca fabae). Ohio State University. M.S. Thesis. Gui, H.L., 194-5. Susceptibility of bean varieties to insect infestation. Ohio Expt. Sta. Bui. 659; 112-113. Hallowell, E.A., and H.W. Johnson, 1934-. Correlation between rough hairy pubescence in soybeans and freedom from injury by Empoasca fabae..Phytopathology 24: 12. Hayes, K.H. and F.R. Immer, 1942.Methods of plant breeding. McGraw Hill Book Col, Hew York. Horber E., 1955. Oviposition preference of Meromyza americ- ana Pitch for different small grain varieties under greenhouse conditions. Jour. Econ. Ent. 48: 426-30. Horovitz, S., A.H. Marchioni, H.G. Fisher, R.H. Nico and E. M. Sivori, 1952. Informaciones experimentales comple- mentarias sobre la resistencia a la langosta del mai£. Rev. Argent. Agron. 19: 208-13 (P.B.A. 23: 1941). Ibbotson? A. and J.S. Kennedy, 1950. The distribution of aphid infestation in relation to leaf age. II The ■progress of Aphis fabae Scop, infestations on sugar beet in pots. Ann. Applied Biol. 37: 680-96. Ishii, S., 1950. Studies on the host preference of the cow- pea weevil (Callasa = Bruchus chinensis L.) VIII' (In Japanese with English summary) Oyo-Kontyu 6(1):'35-40. (B.A. 28: 12135). Jewet, H.H., 1929. leafhopper injury to clover and alfalfa. Kentucky Agr. Exp. Sta. Bui. 293: 157-72. Johnson, H.W., 1934. Nature of injury to forage legumes by potato leaf hopper. Jour. Agri. Res. 49: 379-406. Johnson, B., 1953. The injurious effects of the hooked epi­ dermal hairs of french beans (Phaseolus vulgaris L.) on Aphis craccivora Kock, Bull. Ent. Res. 44: 779-88. Kennedy, J.S., 1950. Host-finding and host alteration in aphids. Int. Congr. Ent. Stockholm. (1948) VIII th: 423-26. 1951. Host plant selection in aphididae. Internatl. Congr. Ent. Trans. IXth: 106-13* -104- Kennedy, J,S. and C.O. Booth, 1951• Host alternation in Aphis fabae Scop. I, Feeding preferences and fecun­ dity in relation to the age and kind of leaves. Ann. Appl. Biol, 58: 25-64 (H.A.E. 39: 198). Khanna, K.L. and S.l. Sharma, 1949. Lower epidermis of leaf midrib as an indicator of its hardness in sugarcane. Proc. Indian Acad, Sci. Sec.B. 30: 307-15 (P.B.A. 21: 1214).

Krishnamurti, T.S., 1951* Improved varieties of oilseeds sesamum. Indian Fug. 1 (9): 22-23 (P.B.A. 22: 2162). Lefevre, P.O., 1950. Bruchus obtectus Say. Ou bruche des haricots (Phaseolus vulgaris L.) Publ. Inst. Nat, Agron, Congo Beige 48: to 5. (P.B.A. 21: 735)* Le Eoux, E.J., 1954. Effect of various levels of nitrogen, phosphorus and potassium in nutrient solution on the fecundity of the two spotted spider mite. Tetranychus bimaculatus Harvey, (Acarina: Tetranychidae) reared on cucumber. Canad. J. Agric. Sci. 34(2): 145-151* (B.A. 29: 9715). Lipke, H. and G. Fraenkel, 1956. Insect nutrition. Annual Rev. Ent. 1: 17-44. Maltois, J.B., 1951* The nitrogen content of different va­ rieties of peas as a factor affecting infestations by Macrosiphum pisi (Kalt.) (Homoptera aphididae). A pre­ liminary report. Canad. Ent. 83: 2933. May, A.W.S., 1951. Jassid resistance of the cotton plant, Qd. J. Agric. Sci. 8: 43-68. (R.A.E, 41: 406). Mcbean, D.S. and A.W. Platt, 1951* Differential damage to barley varieties by grasshoppers. Sci. Agric, (Ottawa) 31 (4): 162-75. (B.A. 25: 57935). McKelvey, J.J.Jr., J.C. Guevara and A. Cortes, 1947. Apion pod weevil: A pest of beans in Mexico. Jour. Econ. Ent. 40: 476-79. Medler, J.T. and A.R. Albert, 1953* The relationship bet­ ween populations of alfalfa insects and soil treat­ ments with boron. Jour. Econ, Ent. 46: 793-97* Oman, P.W., 1949. The Neartic leafhoppers. A genetic clas­ sification and check list. Ent. Soc. of Washington. 253 pp. -105- Painter, R.H., 194-1. The economic value and biologic signif­ icance of insect resistance in plants. Jour. Econ. Ent. 54-: 358-67. 1951. Insect resistance in crop plants. The Macmillan Co. New York. 520 pp. . 1951a. The role of nutritional factors in host plant selection. Internatl. Cong. Ent. Trans. IXth (2): 101- 105. 1954-. Some ecological aspects of the resistance of crop plants to insects. Jour. Econ. Ent. 4-7: 1036-4-0. Packard, C.M. and J.H. Martin, 1952. Resistant crops, the ideal way. U.S.D.A. Ybk: 4-29-36. Parnell, P.R., 1935* Origin and development of the U4- cot­ ton. Empire Cotton Growing Crop. Rev. 12: 177-82. Pearson, O.H.? R. Hopp and G.W. Bohn, 1951. Notes on species crosses in cucurbita. Proc. Amer. Soc. Hort. Sci. 57: 310-22 (P.B.A. 22: 1516). Ponnaiya, B.W.X., 1951. Studies in the genus Sorghum. I. Field observations in sorghum resistance to the insect pest, Atherigona indica M. Jour. Madras Univ. 21 Sect. B: 96-117 (p Tb .A. 22: 1957). Pieters, A.J., 1928. Red clover's hairiness in American types is due to the leafhoppers. U.S.D.A. Ybk: 521-24-. Poos, F.W. and F.F. Smith, 1951. A comparison of oviposition of nymphal development of Empoasca fabae (Harris) on different host plants. Jour. Econ. Ent. 24-: 361-71• Poos, F.W. and N.H. Wheeler, 194-3. Studies on host plants of the leafhoppers of the genus Empoasca. U.S.D.A. Tech. Bull. No. 850. 51 PP. 194-9. Some additional host plants of three species of leafhoppers of the genus Empoasca (Homoptera Cicadelli- dae). Proc. Ent. Soc. Wash. $1 (1). Reid, W.J., 194-0. Biology of the seed maggot in the coastal of the South Atlantic States. U.S. Dept. Agr. B.E.P.Q. Tech. Bui. 723. Ristich, S.S. and H.H, Schwardt, 194-9. Biology and control of the seed corn maggot on beans in New York. Jour. Econ. Ent. 4-2: 77-80. -106- Roberts, D.W.A., 1954-. Sawfly resistance in'wheat. I. Types of resistance. Canad. Jour. Agr. Sci. 34- (6): 582-97.

Schaerffenberg, B,, 1955* Observations on Colorado beetle Leptinotarsa decimlineata (Say). Zeitschr Pflanzenkrankh ZrxW. 67- 757— ------Scharff, D.K., 1954-. The role of food plants and weather in the ecology of Melanoplus mexicanus mexicanus (Sauss). J our. Ec on. Ent. 47: 485-89“! Sloan, W.J.S., 1938. Cotton jassids or leafhoppers. Qd. Agr. Jour. 50: 450-55- Smith, P.P., 1935. The nature of the sheath material in the feeding punctures produced by the potato leafhopper and the three-cornered a-lfalfa hopper. Jour, Agri. Res. 47: 475-85. Smith, F.F. and F.W. Poos, 1931* The feeding habits of some leafhoppers of the genus Empoasca. Jour. Agr. Res. 43: 267-85. Stevenson, F.J. and H.A. Jones, 1953. Some sources of re­ sistance in crop plants. U.S.D.A. Ybk: 192-216. Strand, S.B., 1943. Species crosses in the genus Phaseolus. Amer. Soc. Hort. Sci. Proc. 42: 569-73. Suneson, C.A. and J. Bernarr, 1953. Resistance reactions to the hessian fly on the California-Mexico border. Agr. Jour. 45: 172-74. (P.B.A. 23: 2538). Taylor, L.F., J.W. Apple and K.L, Berger, 1952. Response of certain insects to plants grown on varying fertility levels. Jour, Econ. Ent. 45: 843-48. Taylor, L.N., 1958. Pubescence inheritance and leafhopper resistance relationships in alfalfa. Agr. Jour. 48 (2): 78-8 1 . Thorsteinson, A.J., 1953* The chemical sense in phytophagous insects. Redia (ser.2) 38: 369-74-. 1953a. The role of host selection in the ecology of phytophagous insects. Canad. Ent. 85: 276-82. Turner, K., 1951. Relation between sugar content of corn and infestation and survival of the european corn borer. Jour. Econ. Ent. 44: 307-09. -107- Wilson, M.C., R.L. Davis and G.G. Williams, 1955* Multiple effects of leafhopper infestation on irrigated and non-irrigated alfalfa. Jour. Econ. Ent. 48: 325-26. Wingard, S.A., 1955* Nature of resistance to disease. U. S. D.A. Ybk: 165-73.

Verma, S.C. and P.S. Mathur, 1950* The epidermal charac­ ters of sugarcane leaf in relation to insect pests. Indian Jour. Agric. Sci. 20 (5): 387-89 (B.A. 26: 13361). Yarnell, S.H., 1952. Breeding for resistance to the ear- worm in sweet corn, Proc. Ass. Sth. Agric. Wkrs. 49: 106-07 (P.B.A. 23: 797). SELECTED BIBLIOGRAPHY. General papers

Chesnokov, P.G., 1955* Resistance of Agriculture plants to pests. Leningrad, 30 pp. (Bibliography of agricul­ ture 423 C 424 U). Carter W,, 1952. Injuries to plants caused by insect toxins. II. Bot. Rev. 18: 680-721. Dethier, V.G., 1954. The phisiology of olfaction in insects. N. Y. Academy Sci. Ann. 58: 159-57* Erost, S.W., 1955* The numerical relationships between phytophagous insects and their hosts. Sci, Mon. 79: 10-12. Heckel A., 195^. When does an insect become a pest? Bio- Dynamics 12 (2): 6-12. Levinson, A. H., 1955* Nutritional requirements of insects. Riv. di Parasitol. 16: 113-38. Megalov, V.A., 1954. Regulation of metabolism in plants as a method of decreasing the fertility of the piercing- stabbing (insects) pest of agricultural crops, (In Russian) Timiriazevshaia Sel'shohhoz. Ahad Szv. 2 (6): 157-166. Nuorteva, P., 1952. Host plant selection in insects in the light of investigations made on leafhoppers. Ann. Acad. Sci. Eennicae, Ser. A 19: 1-90 (B.A. 28: 15757)* Ramachandran, S., 1952. Manuring in relation to insect pests. Madras Agr. Jour, 39: 91-95* Strickland, A.H., 1954*. The assessment of insect pest den­ sity in. relation to crop losses. Commonwealth Ent. Comf. Rpt. 6: 78-83. Yuasa, H., 1952. Growth habit of crop plant as an environ­ mental factor of insect pests. Internatl. Congr. Ent. Trans. IXth. (1): 810-12.

Cereals in general,

Arriaga, H.O., 1954. Resistancia a la Toxemia de Schiza- phis = Toxoptera graminum (Rond) en cereales finos. Rev. Eac, Agr. Eva Peron, Buenos Aires. 30; 65-101.

-108- -109- Anon., 194-9. Ensayos de resistancia a la saliva toxica del pulgon verde de los cereales, sobre avena, cebada y centeno. Inform. Invest. Agric, (I.D.I.A.) 2 (20): 18-19. Buenos Aires,

Corn.

Beck, S.D., 1953* Nutrition of the european corn borer Pyrausta nubilalis (HBN). III. An unidentified dietary factor required for larvae growth. Jour. Gen. Physiolv 36: 317-25. (R.A.E. 44-: 315). Beck, S.D. and J.H. Lilly, 1949. Report on european corn borer resistance investigations. Iowa St. Coll. Jour. Sci. 23: 249-59. Burkhardt, C.C. and R.H. Painter, 1954. Weight differences in southwestern corn borer larvae, Diatraea grandio- sella, Dyar, reared on teosinte in Kansas i n 1952. Jour. Kansas Ent. Soc. 27 (1): 21-23. Busquets, M.A., 1954. La resistancia de lineas del rnaiz al taladro. An. Estac. Explt. Aula Dei (Spain) 3 (2): 247-52. Dicke, P.P. and L.H. Penny, 1952. Built-in resistance helps corn fight borers. Crops and Soils 4: (9) 9-11 (P.B.A. 23: 1207). Pleming, A,A., 1952. Inheritance of characters in corn with special reference to the european corn borer. Diss. Abstr, 12 (3086) 121. (P.B.A. 23: 1940). Haskel, G., 1951* Studies with sweet corn. The frit fly problem. Bull, Ent. Res. 42: 519-26 (P.B.A. 22: 1564). Melhus, I.E., R.H. Painter and P.O. Smith, 1954. A search for resistance to the injury caused by species of Diabrotica in the corns of Guatemala, Iowa Ste. Coll. Jour, of Sci. 29 (1): 75-94. Painter, R.H., 1955* Insects on corn and teosinte in Guate­ mala. Jour. Econ. Ent, 48: 32-42, Patch, L.H., H.O. Deay and R.O. Snelling, 1951* Stalk breakage of dent corn infested with the August gen­ eration of the european corn borer. Jour. Econ. Ent. 44: 534-39. -110- Penny, L.H. and P.P. Diclte, 1956. Inheritance of resistance in corn to leaf feeding of the european corn borer. Agron. Jour. 4-8 (5): 200-203.

Rosbaco, U.P., 1949. Maices amargos. Inf. Invest. Agric. (I.D.I.A.) 2 (24): 24. Buenos Aires. (P.B.A. 20: 2309).

Rosbaco, U.P., 1951* Consideraciones sobre maices ,,amargos,, con especial referenda a su cultivo en la provincia de Entre Rios. (I.D.I.A.) Buenos Aires 4 (46): 1-13. (P.B.A. 22: 1899). Weibel, D.E. and R.H. Painter, 1952. European corn borer attacks Kansas on Nebraska sorghum. Crops, and Soils. 4 (4): 22. (P.B.A. 22: 1938).

Wene, G.P., R.A. Blanchard and E.V. Walter, 1953* Relation of corn earworm resistance in sweet corn to efficien­ cy to insecticide sprays. Jour. Econ. Ent. 43: 931-33. Wilbur, D.A., H.R. Bryson and R.H. Painter, 1950. South­ western corn borer in Kansas, Bull. Kansas Agric. Exp. Sta. No. 339. (P.B.A. 21: 317).

Wheat.

Anon., 1952. The yellow wheat midge. Plygbl Vditskyddsanst 98: 4 (P.B.A. 23: 1897). Grafius, J.E. and E.R. Hehn, 1950. Pactors associated with grasshopper resistance in four spring wheat crosses. Agron. Jour. 42: 342-44 (P.B.A. 21: 250). Laude, H.H., R.H, Painter and associates, 1952. Ponca winter wheat. Agric. Exp. Sta. Kansas Bull. 354 Oklahoma Bull. B-380. Painter, R.H. and D.C. Peters, 1956. Screening wheat va­ rieties and hybrids for resistance to the Greenbug. Jour. Econ. Ent. 49: 546-48. Wall, A., 1952, The diameter of the wheat stem in relation to the length and sex of the emergin sawfly (Cephus cinctus) Sci. Agr. 32: 272-77 (Ottawa). (R.A.E. 40:

38577“ -111- Oats and Barley

Akerman, A., 1951* Some findings regarding frit fly larvae attack on oats. (In Swedish) Sverig Uts&desforen Tidskr 61: 108-18. (P.B.A. 22: 316). Dorfschmid, M. , 1952. Investigations on oats concerning at­ tack by frit fly, Oscinella frit L. Z. Acker-u PflBau 95: 183-218 'P.B.A".' 23: '2?2)7 Hill, C.C., W.B. Cartwright and G.A. Wiebe, 1952. Barley varieties resistant to the hessian fly. Agron. Jour. 44: 4-5. (P.B.A. 22: 1930).

Sugar cane, sorghum and grasses.

Boerger, A . , 1952. 0btenci6n en nLa Estanzuela" de un Lolium multiflorum resistente a Schizaphis graminum. y Puccinia coronata. Arch. Pitotec. Urug. 5: 155-56. (PTETA'r23:"r2437'_ Dahms, E.G. and J.B. Sieglinger, 1954. Reactions of sorghum varieties to the chinch bug. Jour. Econ. Ent. 47:536- 37. Ju, L.S., 1953* An investigation of P.T. varieties attacked by certain borers (In Chinese English summary) Jour, sugar cane Res. 7: 45-61. Samuel, C.K. and S. Chetberji, 1953* Studies on the va­ rietal resistance and susceptibility of "Jowar” (An- dropogon sorghum) to storage pests in India. Indian Jour. Ent. I?:.225-39. (R.A.E. 43: 152). Williams, J.R., 1949. A discussion on the present status of the sugar-cane pest Clemora (Phytalus) Smithi in Mau­ ritius. Rev, Agric. Maurice 28: 292-95 (P.B.A. 20: 2492).

Rice and Millet

Kawada A., 1954. Insect resistance of Japanese rice plant. Jap. Jour. Breeding 4: 151-165* Kobayashi, M. , 1946. Varietal differences in degree of Bylemya injury in Pearl Millet (In Japanese) Proc. crop. Sci. Soc. Japan. 15: 28-32 (P.B.A. 20: 2330). -112- Seko, H, and I. Kato, 1950. Studies on the resistance of rice to Chilo simplex. I, II and III (In Japanese) Nippon Sokumotsugaku Kai Kiji 19 Nos 1/2: 201-08. (P.B.A. 22: 1956, 1957, 1958). Yuasa, H., 199-9. Resistance in rice plant to the rice stem maggot. Mats. 24: 482-695. (R.A.E. 59: 500). Beans and Soybeans

Freytag, G.F., 1955* Variation of the common bean (Phaseo- lus vulgaris L.) in Central America. Mss . Abs. 15: £53) pV 6 7 ^ (P.B.A. 26: 2116). Johnson, H.W. and E.A, Hollowell, 1955* Pubescent and gla­ brous characters of soybeans as related to resistance to injury by the potato leafhopper. Jour. Agr. Res. 51: 571-81. Knapp, 0., 1941, Contribution to the problem of breeding for quality and for immunity in dwarf beans. Ziichter 15: 19-21 (P.B.A. 11: 840). McFarlane, J.S., H.H. Reiman, 1945. Leafhopper resistance among the bean varieties. Jour. Econ. Ent. 56: 659. Rios, P., and A, Riollano, 1946. The improved of native white beans (Phaseolus vulgaris) by selection. Amer. Soc. Hort. Sci. Proc. 4§T 425-56. Suenaga, H,, K. Matsuo and H. Sakoi, 1951. Varietal dif­ ferences in the damage caused to broad beans by the broad bean weevil (In Japanese) Kyushu Agric. Exp. Sta. 1-82. Watson, J.R., et al, 1933* Resistance of beans to Empoasca Fla. Agr. Exp. St. Ann. Rpt. 1931-1932: 69-91.

Vegetables

Auclair, J.L. and J.B. Maltois, 1950. Studies on the re­ sistance of plants to aphids by the method of paper partition chromatography. Canad. Ent, 82 (8): 175-76. Lamb, K.P., 1953* Observations on yield and varietal sus­ ceptibility of some carrot varieties to insect attack in the field. N.Z. Jour. Sci. Tech. 54: 531-37 (P.B.A. 23: 3023). -113- 1953a. Eield trials of five swede varieties witli special reference to aphid resistance* N.Z. Jour. Sci. Tech* 35: 135-4-5 (R.A.E. 43: 233). Muller, H.J., 1951. On the causes of the differences in the resistance of Vicia fabae L. to the "bean aphid Doralis fabae Scop, to choose i-bs host. (In German') Zuchter .2ITT61-79 (P.B.A. 22: 826). Wright, D.W., Q.A. Guering and J.A. Dunn, 1951. Varietal differences in the susceptibility of peas to attack by the pea Laspe.yresia nigricana (Steph) Bull. Ent. Res. 41: 663-7?.

Potato, Sweet Potato and Egg Plant. Bradley, R.H.E. and R. Y. Ganong, 1952. Aphid infestations on katahdin and on a seedling resistant to Myzus persicae (Sultz) with two dates of planting. Canad. Jour. Zool. 29: 329-38 (R.A.E. 40: 302). Chauvin, R., 1952. New investigations on the substances that ahtract the Colorado beetle L. decimlineata (Say) towards the potato. Ann. Inst. Agr. Paris 3 (C): 303- 308 (P.B.A. 23: 2032). Goody, J.B.; 1956. Susceptibility of potato varieties to infestation by the eelworms Ditylenchus destructor and D. dipsaci. Ann. Ap. Biol. 44: l6-£4. Granovsky, A.A., and A. G. Peterson, 1954-. Evaluation of potato leaf injury caused by leafhoppers, flea beetles and early blight. Jour. Econ Ent. 47: 894-902. Langenbuch, R . , 1952. Is the lack of a feeding stimulant or the presence of a repellent the cause of resistance of the wild potato Solanum chacoence Bitt to the potato beetle? (In German, English summary)• Z. Pfl. Krankh. 39: 179-89. (R.A.E. 42: 194).’ Peterson, A.G. and A.A. Granovsky, 1950. Feeding effects of Empoasca fabae on a resistant and susceptible variety of pota-fco. Amer. Potato Jour. 27: 366-71 (P.B.A. 21: 1165). Plapp, R.W., 1953- Resistance in wild species of Solanum to the leafhopper, the flea beetle and the common aphids of potato. Ohio State Univ. M.S. Thesis. -114- Schaper, P., 1953* Contribution on the resistance of Sola­ num chacoense (Bitt) to Colorado beetle L.- decimlineata (Say). Zttchter 23: 115-21 (P.B.A. 23: 28Ul. Tanaka, M, and S. Sakai, 1950* Studies on artificial poly­ ploid egg plants II. An experiment on the insect re­ sistance of the uonumashibai egg plant (In Japanese) Seiken Jiho (Biological Report) 4: 59-65 (P.B.A. 22: 820 and 822). Torka, M,, 1950. II. Breeding potatoes with resistance to the Colorado beetle. Amer. Potato Jour. 27: 263-71* (P.B.A. 21: 4-25). Toxopeus, H.J., 1949. The significance of resistance in tuber-bearing wild Solanum species for the breeding of a commercial potato resistant to the Colorado beetle. Progress Report for the meeting of the Comite Europeen d'Etudes de Zoologie Agricole. (P.B.A. 21: 426). 1953* Report on the possibilities of breeding potato varieties that are not attacked by the Colorado beetle (Mimeographed)(3 papers)(P.B.A. 23: 467, 468, 469).

Alfalfa

Davis, R.L. and M.C. Wilson, 1953. Varietal tolerance of alfalfa to the potato leafhopper. Jour. Econ. Ent. 46: 242-5. Harvey, T.L. and H.L. Hachrott, 1956. Apparent resistance to the spotted alfalfa aphid selected from seedlings of susceptible alfalfa varieties. Jour. Econ. Ent. 49: 289-91. Jones, L.G., P.1T. Briggs and R.A. Blanchard, 1950. Inheri­ tance of resistance to the pea aphid in alfalfa hy­ brids. Hilgaria 20 (2): 9-17. (R.A.E. 40: 63). Wilson, M.C. and R.L. Davis, 1953. Varietal tolerance of alfalfa to the meadow spitlebug. Jour. Econ. Ent. 46: 238-41. -115- Cotton

Knight, R.L., 1952. The genetics of jassid resistance in cotton. Jour. Genet. 51: 4-7-66 (P.B.A. 23: 2823). Muhammad, A, and M.A. Ghana, 194-9. Studies on the cotton jassid (Empoasca devastans Dist) in the Punjab XI. Effect of agronomic factors on the incidence of jas- sid attack. Pakistan Jour. Sci. Res. 1: 4-1-62 (P.B.A. 22: 551). Nazir, A.M.A. and M.A. Ghani, 1950* Studies on cotton jas- sid (Empoasca devastans Dist.) in the Punjab XII. PakisF. Jour. Sci. 2: 117-20 (P.B.A. 23*. 4-93). Richmond, T.R., 1955. Puture may give us insect resistance in cotton. Cotton Gin. & Oil Mill Press 54 (6): 28,30. Sun, E.M., 1951. The utilization of uplands cotton varie- ■ ties tolerant of insects (In Chinese) Nungyeh Yenchiu (Agric. Res.) Taipeh 2 (2): 51-68 (P.B.A. 22: 284-7).

Grapes, Berries, Citrus and Apples

BURNER, C., 194-9. The hereditary principles involved in attacked and freedom from attack of plants by insect parasites. NachrBl. Dtsch. PflSchDie'nst 3: 121-30. (P.B.A. 21: 665). Breider, H., 1950. Morphological resistance characters of vines leaves (In German) Ziichter 20: 210-12 (P.B.A. 21: 1375. Cebrii, M.P., 1950. The use of local varieties of vines in hybridization, Vinodelie Vinogradarstvo U.S.S.R. 6: 25-26. (P.B.A. 20: 26430). Fleschner, C.A., 1952. Host-plant resistance as a factor influencing population density of citrus red mites on orchard trees. Jour. Econ. Ent. 45: 687-695. Kronenberg, H.G. and E.J. De Pluiter, 1951* Resistance of raspberries to the large raspberry aphid A. rubi Kalt. Tijdschar Plziekt 57: 114-23 (P.B.A. 22: 1422). Princ, J.A., 1950. I. The control of pests and diseases of the grape vine. Vinodelie Vinogradarstvo. U.S.S.R. 6:54-57* (P.B.A. 20: 2642). -116- Sokolov,^A.M. and R.A. Sokolova, 1952. The role of the os­ motic pressure of the cell sap in the resistance of apple to the green aphid Aphis pomi Deg. (In Russian) Dokl Vsesoyuz. Akad. Sel-khoz. Rank Lenina 17: 12-18 (R.A.E. 41: 257). Wilcox, R.B., 1951. Tests of cranberry varieties and seed­ lings for resistance to the leafhopper vector of false blossom disease. Phytopathology 41: 722-55.

Woods

Walcott, G.R., 1948. The resistance to dry-wood termite at­ tack of some Central American woods. Caribb Eorester 9: 53-54. Rio Piedras. (R.A.E. 39: 60). AUTOBIOGRAPHY

I, Jose Guevara Calderon, was ‘born in Zaragoza, Coa- huila, Mexico, about 50 miles from the United States bor­ der, on December 8, 1919* I received my elementary education in my home town. The equivalent of high school was finished at the Practical Agricultural School of Galeana, Nuevo Leon. Studies at the National Agricultural School in Chapingo, Mexico, led to the receipt of the degree Ingeniero Agrono- mo, equivalent to the degree Bachelor of Science. My first job was on the biological control of the citrus blackfly in Cuernavaca, Morelos. In 194-5 I was commissioned by the Mexi­ can Federal Government to work with the Agricultural Experi­ ment Station in Chapingo, State of Mexico, and other sub­ stations in the central part of Mexico. One and a half years were spent working in plant breeding, one and a half years in entomology, and seven years as manager of the Experiment Station. During the last four years in Mexico I taught gen­ eral entomology at the National Agricultural School. I was married in 194-7 and obtained the degree Master of Science in 1949 at Ohio State University.

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