ARS | Publication request: Use of DNA barcodes to identify invasive armyworm Spodoptera species in Florida

Submitted to: Journal of Insect Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 17, 2010
Publication Date: January 20, 2011
Citation: Nagoshi, R.N., Meagher Jr, R.L., Brambila, J. 2011. Use of DNA barcodes to identify invasive Spodoptera species in Florida. Journal of Insect Science. 11:154.

Interpretive Summary: Army worms nclude some of the most important pests of agricultural crops in the world. These are commonly known as “armyworms” because severe infestations can appear as large masses “marching” in search of food. As many as 30 species have been identified with members present in all six continents. Posing the greatest invasive threat to the U.S. according to the USDA are the Egyptian cotton leafworm, and the tobacco cutworm. Both species produce economically significant damage to a range of crops, most notably cotton, soy bean, maize, rice and ornamentals. Each has a wide geographical distribution, extending into southern Europe, Africa, much of Asia. It is predicted that both species have the potential to become established in much of the southwestern and southeastern U.S., reaching as far north as Maryland, with annual migratory potential into the northern states and Canada. Given these concerns methods are required that can rapidly and accurately distinguish these invasive army worms from related domestic species with similar appearance. Unfortunately, most diagnoses require microscopic examination of adult genitals, a tedious procedure that requires substantial sample preparation and undamaged specimens. Therefore, finding an alternative method is of interest. Scientists at the USDA/Agriculture Research Service, Center for Medical, Agricultural, and Veterinary Entomology, Gainesville, Florida, have proposed DNA barcoding as a molecular means of identifying invasive organisms. The objectives of this study were to develop a barcoding reference library for the relevant armyworm species and determine whether sufficient barcoding gaps exist between them to allow their unambiguous discrimination by this method.

Technical Abstract: A critical component for sustaining adequate food production is the protection of local agriculture from invasive pest insects. Essential to this goal is the ability to accurately distinguish foreign from closely related domestic species, a process that has traditionally required identification of diagnostic morphological “keys” that can be both subtle and labor-intensive. This is the case for Spodoptera, a genus of Noctuidae moths that includes several important agricultural pests, making timely monitoring of invasive populations difficult. Two of the most destructive species, S. litura and S. littoralis, are not established in North America and preventing their introduction into the United States is a high priority. To facility the monitoring of these and other old world Spodoptera, DNA barcoding methodology was tested for its effectiveness in distinguishing between domestic and foreign Spodoptera species. The data presented here indicate that this technique can be an efficient and accurate supplement to existing methods for the identification of invasive Spodoptera pests.