A New Pest Op Alfalfa in Mexico
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STUDIES ON THE BIOLOGT, ECOLOGY, DISTRIBUTION, AND CONTROL OP EPICAERUS AURIFER BOH. (CURCULIONIDAE), A NEW PEST OP ALFALFA IN MEXICO Dissertation Presented In Partial Fulfillment of the Requirements for the Degree Doctor of Philosophy in the Graduate School of The Ohio State University By George Mallory Boush, B. Sc., M. Sc. The Ohio State University 1955 Approved by Adviser DeDpeapratrmtemnetn tof ofZo oZlool and Entomology ACKNOWLEDGEMENTS The author wishes to express his sincere appreciation to Dr* D# M# DeLong, Department of Zoology and Entomology, The Ohio State University, for his inspirational guidance and counsel in connection with this study and to Drs# Douglas Barnes and John J# McKelvey of The Rockefeller Foundation for their advice and encouragement# Grateful acknowledgement is also made to Mr# Francisco Gonzolez and Miss Carlota Riess H#, Mexican Agricultural Program, for their assistance in preparing the drawings; and to Miss Rose E. Warner, Dr# E# W# Baker, Entomology Research Branch, U.S#D#A., Dra# Helena Brava and Dra# Leonila Vasquez G#, University of Mexico, for determining the species of insects, mites, plants, and mammels res* pectively as referred to in this dissertation; and to Mr# E. L# Sleeper who assisted in the preparation of the section on taxonomy# I should also like to thank The Rockefeller Foundation for making this study possible# Finally, I should like to express my heartfelt gratitude and thanks to my wife, Sara, for her constant help and encouragement# ii Table of Contents Page Introduction............ 1 Taxonomy .......................... 6 Description of the S t a g e s ........................... 8 A d u l t .................... ....... 8 Egg ............................................. 12 Larva ....... 13 Pupa ........ 15 Life History and Habits ..... 17 Adults .......................................... 17 Qnergence ....... 17 Sex Ratio ........... 18 Mating ............... 21 Preoviposition Period .... 22 Ovlposltlon .... 23 Number of Eggs and Egg Masses Laid per Female 27 Longevity ..... 28 Description of Damage .... 30 Behavior Studies ......... 31 Eggs «.................................. 32 Incubation Period .... 32 Egg Development and Hatching............. 36 ill Page Larva ••••••....... 37 Number of Instars ......... •................ 37 Description of Damage . ♦♦♦ 3d General Habits .............................. I4I4. Pupa ....................... I4.6 Host and Food Plants ............ ........ I48 Natural Enemies ........... 53 Predators .................. • 53 Parasites........ ........ ..... .... 57 Population Dynamics ............ ••••••• ....«» 57 Distribution Studies ..... »••• 60 General Description of the Area Studied ...... 60 Method of Determination ......... 6 7 Control ....*• 78 Cultural .............. 78 Chemical ........ 78 Laboratory ...................... 78 F i e l d ........................................... 80 Summary and Conclusions ........ 89 Appendix .... 93 Literature Cited ......... 100 Autobiography ..... • 102 iv Introduction The present study concerns the biology, ecology, distribution, and preliminary control studies of the curculio, Eplcaerus aurlfer Boh*, over a 2-year period in south-central Mexico* Prom the time of the original description of this insect by Boheman (IQJ4.O) until the present, no work, other than Its inclusion in taxonomic treatises is known. However, three other species of the genus Eplcaerus; E* lmbrlcatus (Say), E. cognatus Sharp, and E* formidolosus Boh. are recognized as pests of agricultural crops. Eplcaerus lmbrlcatus. the imbricated snout beetle, attacks a wide range of crops In the United States, especially apples, potatoes, and strawberries; also E* cognatus is a serious pest of potatoes In the highlands of Mexico. The genus is apparently indigenous to the Americas. All of the species recognized by Leng (1920) and Blackwelder (l9i^7) were originally described from the southern portion of the United States, Mexico, and Central America* Although not yet recorded in the literature, E. aurlfer, in the larval stage, is a geographically res tricted but highly destructive pest of alfalfa* The adult beetle also attacks the foliage of alfalfa as well as the foliage of corn, soybeans, and field beans* However, the principal damage to alfalfa is by the feeding of the larvae on the primary root of the plant. 1 This tunneling and boring eventually results in the weakening or destruction of the plant. Attacks by this pest on a commercial basis result in a progressive dieback or loss of stand in previously well established alfalfa fields. Usually, heavily infested fields are abandoned or plowed under aa a result of these attacks* Its importance as a potential major pest can be further realised when it is noted that alfalfa, under irrigation, is the most important forage crop grown in Mexico. Alfalfa, as food for cattle, forms the basis for the dairy Industry. Its productivity is high. When properly cared for and under favorable conditions it may remain in production for 5 to 7 years, annually producing as many as 9 or 10 cuttings. In addition, certain areas of Mexico are famous for the production of high quality alfalfa seed* This problem was undertaken largely because of the potential economic importance of this Insect and because of the lack of information concerning its habits, range, and control* Inorder to carry out studies on various aspects of the biology, ecology, distribution, and control of E. aurlfer. the author established a program of field and laboratory experiments. Life history studies, pop ulation dynamics, movement studies, biological control, and determination of range and large plot control tests were done in the field* The laboratory studies included all physical measurements as well as determination of the incubation period, longivity, egg-laying habits, food plant preferences, and preliminary laboratory control experiments* As there is no published data concerning the location and size of commercial alfalfa growing regions of Mexico, a program was also undertaken in which the author visited and mapped these areas* To facilitate the studies on the biology and control °? aurlfer it was essential to obtain permission to utilize an area heavily populated with this insect* For insectary work on longevity, egg laying studies, and laboratory insecticide screening, it was necessary to be able to obtain several thousand individuals of approximate known age at a given time. Similar land was needed for field use in biological and insecticidal control studies as well as population studies* La Patera, a dairy farm of approximately 200 acres, located on the northern outskirts of Mexico City, was found to be heavily infested with E. aurlfer* The owner of the farm, Mr* Francisco McCann, was greatly concerned over the possible depredations of this Insect and gener ously consented to make available land and labor for experimental purposes. The farm was completely irrigated and planted in corn and alfalfa* k In late April 1952, on the McCann farm, a lj. acre field of 3 year old alfalfa of the variety Oaxaca was found to be particularily heavily infested with E* aurlfer* This field was immediately designated as a biological and population study area and efforts were made to keep it in as undisturbed condition as possible* During the spring and summer of 1 9 5 2 and 1953 this field was obser ved and examined twice each week. During the remainder of the year the field was examined at approximately weekly intervals* The progress of the various life stages was largely determined by examination of 10 plants, selected at random, in the above field at regular weekly intervals* The larvae and pupae collected at this time, together with collection data, were placed in vials containing Peterson* 8 (1914-7) K.A.A.D. solution and later transferred to 80 per cent ethyl alcohol* These specimens were later measured and carefully observed for possible parasites* Samples of plant tissue damaged by this curcullo were also collected at the same time and placed in 8 0 per cent alcohol for more critical observation In the lab oratory* Measurement of adult population fluctuations were secured by placing five 1 square meter quadrats, at weekly Intervals, during the rainy season on the alfalfa field designated for biological studies* 5 A similar alfalfa field, located adjacent to the biological studies field, was utilized for control exper iments* One portion of this field was used to determine the effects of overgrazing in controlling this pest* An equal portion was used to determine the effects of flooding in controlling E. aurlfer* Also at La Patera, insecticide treatments were applied to the soil of seedling alfalfa on a field basis as well as foliar applications of various insecticides to fields of alfalfa infested with adult curculios* All of the insectary and laboratory tests on E. aurlfer were carried out at the Agricultural Experiment Station at Chapingo located 23 miles southeast of Mexico City at the National School of Agriculture* Adequate greenhouse and insectary facilities were available at Chapingo for these studies* Specimens collected at La Patera were brought to Chapingo for more critical biological studies* Cages were also constructed at Chapingo in the insectary to house various small mammals utilized in natural predator studies* 6 Taxonomy Eplcaerus aurlfer Boheman (Original Description) Boheman, C.H. l81j.O. Schoriherr Genera et Species, Curculionidium, Vol. VI, Part 2, p. 278. Eplcaerus aurlfer Boheman Sharp, David. 1891.