Semester of Graduation

Summer 2019

Degree

Master of Science (MS)

Department

Entomology

Document Type

Thesis

Abstract

Cylas formicarius elegantulus (Summers) and Euscepes postfaciatus (Fairmaire) are the most destructive sweetpotato weevils in the Caribean Basin. However, damage occurring in sweetpotato production in Haiti is attributed to C. formicarius (S), since it is known to be the most prevalent species while, conflicting information is available pertaining to the occurrence of the E. postfaciatus (F). This study was conducted in the summer of 2018 to determine the presence or absence of E. postfaciatus (F) in Haiti. 98 weevil samples from field (70% ) and infested sweetpotato roots from field and regional markets were collected (30%) in the most relevant sweetpotato production regions in Haiti. Based on morphological characters, 100% of the weevils collected were identified as C. formicarius (S) suggesting that E. postfaciatus (F) is not present in Haiti.

Internal transcriptase spacer-1 (ITS-1) region of C. formicarius (S) samples collected in Haiti and Louisiana were used to determine the relatedness among C. formicarius (Summers) biotypes. Cluster analysis displayed high rate of similarities among the ITS-1 regions. The findings also show significant homology between biotypes of Haiti and Hawaii while Louisiana biotypes have no relatedness to those of Georgia, and Hawaii suggesting that updating identification upon C. formicarius biotypes is of high importance for enhancing sanitation and preventing infestation.

C. formicarius larvae are the stage at which the insect causes the highest economic loss in sweetpotato production. Due to cryptic feeding habits of the larvae, insecticide use is limited. Thus, host plant resistance is of high importance as an IPM component for the management of this pest. Resistance traits were introgressed in seventy-one sweetpotato lines and were assessed to determine their resistance level to C. formicarius. Murasaki, 17-221, 16-205 w, 16-209w, 18-194w, 16-213w, and 18-178w are more resistance to C. formicarius than susceptible checks.


Committee Chair

Jeffrey A. Davis

Available for download on Thursday, July 02, 2020

Included in

Entomology Commons

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