SORGHUM AS A HOST OF THE SOUTHWESTERN CORN BORER, Zeadiat~ grandiosella Dyar By JAMES R. GIFFORD rt Bachelor of Science Oklahoma Agricultural and Mechanical College Stillwater, Oklahoma 1956 Submitted to the faculty of the Graduate School of the Oklahoma State University in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE May, 1958 OKLAHOMA STATE UNIVERSITY LIBRARY NOV 5 1958 SORGHUM AS A HOST OF THE SOUTHWESTERN CORN BORER, Zeadiatraea grandiosella Dyar Thesis Approved: Member of the Thesis Committee Member of the Thesis Committee Head of the Department 1 Dean of the Graduate School 409877 ii PREFACE The southwestern corn borer, primarily a pest of corn, has been reported infesting sorghum many times since it was first reported in · the United States in 1930. Little definitive work has been done to determine the importance of this secondary host, since damage to sor ­ ghum by this borer in the past has been of little economic importance. Considering the indirect loss to corn producers due to the possible population increase from sorghum, additional broods by altering the period of larval development (due to different lengths of time required for completing a cycle on the two crops), or sorghum becoming severely infested in the absence of corn, it was deemed feasible to determine the potential of this borer to develop on sorghum. This was especially important if sorghum could serve as a source of overwintered brood, therefore increasing the population of the first generation on corn during the early summer when it is small and susceptible to heavy dam­ age. After a suggestion of this problem by Dr. R.R. Walton, Professor, Department of Entomology, and a discussion with him, Mr. K. D. Arbuthnot 9 Entomology Research Division, United States Department of Agriculture, and Mr. S. D. Hensley, a co-worker and graduate fellow at that time, but presently with the Entomology Research Division, United States Department of Agriculture, the writer decided to initiate a study of this borer on sorghum, with special emphasis on the possibility of its overwintering in this crop. iii Data were taken at Stillwater, Oklahoma, during the period June, 1956 to June, 1957, from five sorghum varieties manually infested at four different ages throughout the summer. I wish to express appreciation to several persons for valuable guidance and assistance during the study as well as in the manuscript preparation. Dr. R.R. Walton, who was instrumental in initiating the study, served as chairman of my graduate committee and gave valuable counsel on experimental procedures and manuscript preparation. Mr. K. D. Arbuthn~ot, who was also instrumental in initiating the study, supervised field research and assisted in obtaihing some of the data. Mr. s. D. Hensley gave valuable suggestions on some phases of the study and assisted in taking some of the data. Mr. Frank F. Davies, Depart­ ment of Agronomy, provided seed of the different sorghum varieties and gave valuable guidance on the agronomic aspects both in the field and in preparation of the manuscript. Drs. D. E. Howell, Head; D. E. Bryan, and F. A. Fenton, Department of Entomology, gave valuable suggestions on preparation of the manuscript. The Department of Entomology provided both field and laboratory facilities and equipment. Finally, I wish to express thanks to my wife, Sue Carol, and to Mrs. Charles Bacon, Jr. who typed and assisted in proofreading the manuscript. iv TABLE OF CONTENTS Chapter Page I. INTRODUCTION. • • • • • 0 • • • . • • • • • • • • • • 1 II. REVIEW OF LITERATURE •• • • 9 • • • • • • • • • • . • • • J Synonymy- e o o o • • • • o • • • • • • • • • o • • • • • 3 Distribution in the United States. • • • • • • • • • • • 3 Description. • • • • • • • • • • • • • • • • • • • • • • 4 Seasonal History. • • • • • • • • • • • • • • • • • • • 5 Habits. • • • • • • • • • • • • • • • • • • 6 Food Plants. • • • • • • • • • • • • • • • • • • • • • • 7 Damage to Plants. • • • • • • • • • • • • • • • • • • • 8 III. METHODS AND MATERIALS. 0 0 0 0 • • 0 • • • . • • • • 9 Varieties of Sorghum • • • • • • • • • • • • • • • • • • 9 Field Layout • • • • • • • • • • • • • • • • • • • • • • 9 Egg Production • • • • • • • • • • • • • • • • • • • 10 Procedure Used to Manually Infest Plants. • • • • • • • 11 Egg Hatch Counts and Plant Measurements. • • • • • • • • 12 Allocation of Infested Plants to Different Phases of the Study. • • • • • • • • • • • • • • • • • 13 Determination of Girdled Plants. • • • • • • • • • • • • 16 Overwintering Observations. • • • • • • • • • • • • • • 16 Emergence of Overwintering Brood • • • • • • • • • • • • 18 Overwintering Brood Fertility. • • • • • • • • • • • • • 19 IV. RESULTS • • • • • • • • • • • e O O 0 • • • • • • • • • • . 21 Development and Survival of Summer Form Borers ••• • • 21 Sorghum Infested During the Vegetative Stage •• • • 21 Sorghum Infested During the Boot to Grain- Filled Stage ••••• • • • • • • • • • • • • • • 25 Sorghum Infested During the Mature Stage •••••• 28 Location of Summer Form Borers on or in the Plants. • • 29 Sorghum Infested During the Vegetative Stage. • 0 • 29 Sorghum Infested During the Boot to Grain- Filled Stage ••••• 0 0 0 0 0 0 0 0 0 0 0 0 0 0 35 Sorghum Infested During the Mature Stage •••••• J6 V Chapter Page Overwintering of Larvae . 9 0 0 ID • • . 37 Location in Plants • • 0 g O O 0 37 Mortality. • • • . J8 Overwintering Brood Spring Emergence •• 42 Survival • • • • • • • • • • • • • • • • • 42 Time of Spring Emergence and Proportion of the Sexes o • o c rQi ,ljl o 4 o o • o 9 .g ~ o 44 Oviposition of Overwintering Brood. 0 Ct 41 0 • • . Extent of Egg Deposition •• 0 @ 0 0 0 0 • • . 46 Time of Deposition ••••• 0 0 0 0 ell . • • 47 Longevity of Overwintered Brood Adults. • • • • . 49 V. DISCUSSION. OOOOIQ1,Q'JOQOQOOO!WJOQIOO~ • • • 51 VI. SUMMARY. ooeoooooo oGooooeoooao 58 LITERATURE CITED •• 000000 0 0 ~ ~ 0 0 0 0 0 O O 0 60 APPENDIX ••••• Qi 9 0 0 0 OOOOfllOOOOO • • 0 63 vi LIST OF TABLES Table Page 1. Date of deposition and placement of eggs on the plants for the four different infestations during the summer •••• • • 12 2. Number and per cent of the different forms of z.. grandiosella Dyar found in vegetative stage sorghum 38-40 days after egg deposition • •••• o • • • • • • • • • • • • • • • • • 22 3. Survival of~. grandiosella Dyar 38 to 40 days after egg de­ position on sorghum infested while in the vegetative stage. 23 4. Survival of borers to moth emergence or immaculate larvae as found on sorghum infested while in the vegetative stage. • • 25 5. Stage of development and survival of larvae on the sorghum varieties Redlan and Hegari found through dissection of five plant samples at different time intervals after egg deposition • •••••• o o •••••••••••••• . 27 6. Fate of larvae on sorghum~ infested at or near grain maturity, as indicated by dissections after declines of temperature to below freezing •••••••••• 0 • • • 29 7. Per cent of the different stages of borers located in various plant parts as found by dissection 38 to 40 days after egg deposition ••••••••••• , ••• . 31 · 8. Numbers of the different instars and stages of borers in the various plant parts 38-40 days after egg deposition as found on plants infested while in the boot stage ••• • • 32 9, Number and per cent of the pupal cases and immaculate larvae found in or below the seventh internode of sorghum. • 35 10. Location of different instar larvae as found on or in the plants of the variety Redlan, infested while in the boot stage . .• e • • • • • • • • • • • • • • • • • • • • • • • • J6 11. Location of immaculate larvae as found during the week of October 27 on sorghum infested when in the vegetative stage. 38 12. Mortality of immaculate larvae above the ground level in standing plants found through periodic dissection during the winter • • • • • • • • • • • • • • • 0 • • • • • • • • • 39 vii Table Page 1.3. Mortality of immaculate larvae below ground, in both girdled and standing plants~ found through periodic dissection during the winter •••••••••••• • • • • .39 14. Comparative mortality of immaculate larvae attempting to hiber­ nate in underground parts of girdled and standing plants as found from periodic dissections through the winter. • • • • 41 15. Comparative mortality of immaculate larvae occurring within dry and moist underground plant parts as found during periodic dissections throughout the winter ••••••• . 42 16. Fate of overwintering larvae in girdled plants of sorghum and corn • • • • • • • • • e • 0 0 0 0 0 • e . • • 4.3 17. Survival of overwintered larvae through moth emergence from girdled plants of the various sorghum varieties. 0 . • . • 44 18. Proportions of sexes of the overwintered brood which emerged from sorghum • • . • • • • • • 0 . • . • 0 . • • • • • • • 45 19. Proportions of sexes of the overwintered brood which emerged from corn. • • • • • 0 0 • • 0 . • . • . • • . 46 20. Fertility and fecundity of female moths emerging from sorghum and corn • . • • • • 0 0 • • • 0 • • • • • • • • • • 47 21. Range of fecundity and fertility of individuals from 22 fertile females overwintered on sorghum and seven over­ wintered on corn • • • • • • • • • • • • • • • • • • • • • • 22. Egg deposition and fertility by number and per cent each night after moth emergence» as found from 22 fertile moths which had overwintered on sorghum. • • • • • • • • • • • • • 50 23. Longevity in days of moths overwintered from corn and from sorghum. • • • o • • • • • • • • • • o • • • • • • • • • • 0 50 viii LIST OF ILLUSTRATIONS Figure Page