Doctor of Philosophy (PhD)



Document Type



Sugarcane aphid, Melanaphis sacchari Zehner, is now widely established in sorghum, Sorghum bicolor L., production areas of the United States and is an important economic pest. However, detailed studies of temperature, host range and plant resistance effects on the biology and population parameters of the M. sacchari biotype responsible for the sorghum outbreak in the United States have not been performed previously. Therefore, the present study aimed to investigate: 1) How temperatures affect M. sacchari 2) M. sacchari interaction with host plants 3) M. sacchari interaction with sorghum genotypes. The response of M. sacchari to six different constant temperatures (15, 20, 25, 30, 32, and 35°C) on sorghum plants was evaluated in the laboratory. Population dynamics and feeding behavior of M. sacchari on six host plants were determined through life table studies and by using the electrical penetration graph (EPG) technique. Twelve sorghum genotypes were screened in laboratory bioassays for potential M. sacchari resistance. From those, seven genotypes were selected and tested in greenhouse and field trials, and feeding behavior was characterized by EPG technique. Population parameters, together with high minimum and maximum thermal thresholds, indicate that M. sacchari is an aphid species more adapted to higher temperatures than other species. Sorghum and Johnsongrass are highly suitable host plants, and sieve element pathway phase is important in host plant selection as well as phloem based factors. Sorghum genotypes PI524770, PI564163, and PI643515 were consistently resistant to M. sacchari. These findings will provide a more robust basis for integrated pest management of M. sacchari on sorghum.



Committee Chair

Davis, Jefrey A.