Semester of Graduation

Spring 2018

Degree

Master of Agriculture (MAgr)

Department

Entomology

Document Type

Dissertation/Thesis

Abstract

The sugarcane aphid, Melanaphis sacchari (Zehntner) (Hemiptera: Aphididae), is an invasive pest of grain sorghum, Sorghum bicolor (L.) Moench. Since its first outbreak in sorghum in 2013, severe infestations have spread throughout the southern U.S. causing high economic losses. While insecticidal control has mitigated some of the impacts of this pest, a sustainable ecology-based management program is needed to reduce reliance on chemical control. We studied the effects of silicon (rates equivalent to 0 and 3360 kg Si/ha) and nitrogen (rates equivalent to 0, 110, and 220 kg N/ha) on M. sacchari growth and reproduction on resistant (DKS 37-07) and susceptible cultivars (DK 38-88) of grain sorghum in a completely randomized factorial arrangement of treatments with five replications in a greenhouse. We calculated life table parameters including growth rate, fecundity, and the intrinsic rate of increase (rm) of M. sacchari for each treatment. A field study with a complete factorial design consisting of 24 treatment combinations (2 cultivars x 4 infestation levels x 3 N fertilization levels) was used. The high rate of nitrogen fertilization increased M. sacchari fecundity, and rm in the greenhouse study, but not in the field study. Sorghum plants with a high rate of N (220kg/ha) had a higher yield. In addition to this, DKS 37-07 resistant cultivar showed a high level of resistance to M. sacchari in both of the studies, and also gave substantial yield. Furthermore, insecticide application at infestation level of 50 aphids/leaf reduced aphid population effectively when compared to the application at bi-weekly and unprotected plots. Finally, Si had no effect on M. sacchari growth and reproduction in the greenhouse study. Results suggest that resistant cultivar if grown with a high level of N (224 kg/ha), and application of an insecticide at low infestation level (50 aphids/leaf) will manage an M. sacchari population thereby maintaining sorghum yield.

Date

4-2-2018

Committee Chair

Reagan, Thomas E.

Available for download on Thursday, March 28, 2019

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