FACTORS INFLUENCING EUROPEAN CORN BORER POPULATIONS IN OHIO DISSERTATION Presented in Partial Fulfillment of the Requirement for the Degree Doctor of Philosophy in the Graduate School of The Ohio State University By MOHAMED TAHIR KIRA, B. Sc., M. Sc. ****** The Ohio State University 1958 Approved by: jffj Adviser Department of Zoology and Entomology ACKNOWLEDGMENTS I wish to express my thanks to Dr. D. M. DeLong, Dr. C. R. Neiswander, and to Dr. L. H. Rolston for their helpful super­ vision, suggestions, and criticisms in the preparation of this dissertation. Special thanks are also due to W. D. Guthrie for furnishing the corn borer egg masses required for this experi­ ment and for helping in obtaining the data presented herein; to C. C. King for his continuous and valuable service in all phases of this problem. The contributions of C. A, Triplehorn and the Statistical Laboratory at Iowa Agricultural Experiment Station were greatly appreciated. I am grateful to Mrs, Hilda Lea for typing the dissertation and to Glenn Berkey and Clarke Robey for their photographic contributions. TABLE OF CONTENTS Page INTRODUCTION. .. ...... 1 REVIEW OF LITERATURE. ....... .... 3 Factors Influencing European Corn Borer Populations . 3 Natural Enemies and the Borer Populations ...... 9 Arthropods . ..................... 9 Enemies other than arthropods. ......... 11 Effect of Corn Resistance or Susceptibility on Borer Populations . 11 Effect of Planting Date on Borer Populations. .... 19 The Damage Done by Borer. .......... 26 PROCEDURES AND TECHNIQUE. .... ......... 35 Preparing the Field of Experiment................... 35 Plot Layout ............... .. Planting and Maintaining the Corn Plants............. 40 Artificial Infestation............ *f0 Hand application................. ^0 Laboratory production of corn borer egg masses . k2. Sampling and Data Recorded. ...... kk RESULTS . k9 Effect of Resistance and Susceptibility on European Corn Borer Populations. ................. 51 First Generation Population. .......... 51 Natural oviposition ....................... 51 Larval establishment and rate of development 55 Page Summer population. ..... 62 Fall Population . » . •• . .. 66 Effect of Date of Planting on European Corn Borer Populations. .............. ...... 71 First Generation Population . .... , * 71 Natural oviposition. 71 Larval establishment and rate of development 72 Summer Population . 78 Fall Population . 79 Combined Effect of Corn Hybrids and Planting Dates on European Corn Borer Populations ....... 8l First Generation Population ..... .......... 8l Fall Population and Second Generation . 90 Damage Done by the European Corn Borer ........ 100 Burrows and Leaf Lesions. .......... 101 Yield • . .. • • . • * . •• 110 SUMMARY. ......................... Il8 APPENDIX . ........................ 120 LITERATURE CITED . ..................... 132 AUTOBIOGRAPHY. ...................... 136 iv LIST OF TABLES Table Page 1. Showing borer population per hundred stalks for all varieties and each planting date, 1926. , and 192*7 $ * • • • * • • • • • • • • • • • • . • • « 2Q 2. Yield of susceptible and resistant varieties. early planted treatment 4 compared with treatment 1. 31 3. Yield of.susceptible and resistant varieties late planted treatment 4 compared with treatment 1. 32 4. Reduction in growth of susceptible plants as a result of borer infestation. Early planting. 33 5 . Reduction in yield of susceptible plants by borer attack............................... • . * 34 6. First generation egg masses by hybrid^ x planting date « . • . •... .. ... « • 32 7» Firsts generation egg masses in hybrids within dates of planting ........................... .. • 53 8. Larval establishment and rate of development in hybrids within dates of planting. Treatment 2. 58 9 . Larval establishment and rate of development in hybrids within dates ofplanting. Treatment 4. 59 10. Midsummer dissection. Analysis of variance. 63 11. Number of first generation borers in hybrids within dates of planting. .. 64 12. First generation pupae in hybrids within dates of planting. ........ 65 13. Fall population. Analysis of variance. 67 14. Fall dissection. Borer population in hybrids within planting dates. .............. 68 15. First generation egg masses in date of planting within hybrids ........... 72 v Table Page 16. Rate of larval development on early and late plants within hybrids. Treatment 2 . 76 17. Rate of larval development on early and late plants within hybrids. Treatment . 77 18.‘ Number of first generation borers in dates of planting xd.th.in hybrids. ............. 78 19. First generation pupae in dates of planting within hybrids * . 79 20. Fall population in dates of planting within hybrids. ..................... 80 21. Rate of larval development in hybrids and piantang date... * • ... «« . .. 82 22. Comparison of larval establishment in treat­ ments 2 , 3 ? and ................ ^5 23. First generation population by hybrids and planting dates .................. 88 2.k. First generation poioulation by treatment in hybrids and planting dates , . 88 25. First generation pupae in hybrids and date of planting ............ 90 26. Fall population. No. of larvae by hybrids and planting dates . ................ 92 27* Fall population. Ho. of larvae within hybrids and dates of planting. .............. 93: 28. Fall population. Ho. of larvae by hybrids and planting dates ••••••••••■■•••»• 93 29* Fall population. Ho, of larvae in hybrids of each planting date in all treatments ....... 93 30. Second generation larval populations. .... 96 31. First generation borer population in treatments 3 and 8 ............ 98 32. Estimate of 1956 second generation larvae on treatment 3» • • ................ 99 vi Table Page 33. First generation borers, burrows, and leaf lesions, in hybrids of each planting date........ 102 34. No. of burrows and leaf lesions in hybrids within date of planting.:(1st generation damage) . 105 35. Ho. of burrows and leaf lesions in dates of planting within hybrids.(1st generation damage). 106 36. No. of burrows in hybrids within dates of planting. (Second generation damage). ....... 107 37* Ho. of burrows in dates of planting within hybrids. (Second generation damage) ........ 108 38. Comparison between first and second generation damage............ ..... 109 39. Effect of first generation infestation on infestation by second generation borers ....... 110 k-0. Yield by treatment within hybrids and dates of planting. .... ... Ill kl. Yield for both hybrids and planting dates. 11^- Comparison between reduction in yield of treat­ ments 3 , 6 , and 8 of both hybrids of the early planting. ................. .......................116 vii LIST OF'APPENDIX. TABLES Table Page 1 . Borers, midsummer dissection. Analysis of variance• 1956•• • • • • .. • • ... .. 120 2 . Burrows, midsummer dissection. Analysis of variance. 1956. ............ 121 3 . Leaf lesions, midsummer dissection. Analysis of variance. 1 9 5 6 ........... .. • • • •.... 122 k. Borers, midsummer dissection. Analysis of variance. 1957* • • • • • • • • • • • • • • • • • • 123 5 . Burrows, midsummer dissection. Analysis of variance. 1957** • • • • • • • •• * •• . 12^ 6 . Leaf lesions, midsummer dissection. Analysis of variance. 1957 • • • • • ............. 125 7. Larvae, fall dissection. Analysis of variance. 1956. .................. 126 8 . Burrows, fall dissection. Analysis of variance. 1956. .......... • 127 9. Larvae, fall dissection. Analysis of variance. 1957. ............... 128 10. .Burrows, fall dissection.. Analysis.of variance. 1957................................................... 129 11. Yield. Analysis of variance. 1956............. 130 12. Yield. Analysis of variance. 1957* * ......... 131 viii LIST OF FIGURES Figure Page 1. First generation natural oviposition on hybrids within dates of planting. 5^ 2 . Effect of resistance and susceptibility on larval establishment. Treatments 2 and A- . 60 3. First, generation natural egg deposition on early and late plantings within hybrids .......... 73 k. Larval establishment on early and late, plantings. Treatments 2 and .............. 75 5» First generation population in hybrids and dates of planting. ....... ... 91 6 . Fall population. No. of larvae by hybrids and dates, of planting. ........................... 9% 7. Second generation population by hybrids and dates of planting. 97 8 . First generation borers, burrows, and lesions in hybrids of each planting date. Treatments. 103 9. First generation borers, burrows, and lesions in hybrids of each planting date. Treatment 4. ..... 104 ix INTRODUCTION The great importance of corn production in many parts of the world has made the ultimate economic effect of the European corn borer, Pyrausta nubilalis (Ebn.), of great concern to the growers of this crop. Differences in the responses of plant varieties to insect attack and the interrelations of plants and insects have been on record for more than a hundred years. Con­ siderable variation was found in the populations of corn borer on different varieties planted on different dates. Apart from the effect of corn hybrids and their planting dates, a complex of Other factors has its effect on borer population as well as other biological populations. These factors are: 1. Physical factors of the environment which could be changes in weather. 2. The genetic characteristics of the host, morphological or physiological, the host abundance, and the agronomic procedu­ res such as time of planting (synchronization), and soil con­ ditions. 3. Biotic factors