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Title: CHRONOLOGICAL AGE-GRADING OF THREE SPECIES OF STORED-PRODUCT BEETLES USING NEAR-INFRARED SPECTROSCOPY

Author
item Perez Mendoza, Joel
item Throne, James
item Dowell, Floyd
item Baker, James

Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/21/2004
Publication Date: 6/1/2004
Citation: Perez Mendoza, J., Throne, J.E., Dowell, F.E., Baker, J.E. 2004. Chronological age-grading of three species of stored-product beetles using near-infrared spectroscopy. Journal of Economic Entomology. 97(3):1159-1167.

Interpretive Summary: The rice weevil, Sitophilus oryzae, lesser grain borer, Rhyzopertha dominica, and red flour beetle, Tribolium castaneum, are the most destructive coleopteran pests of stored cereals and wheat flour in the U.S. and in tropical and warm temperate regions of the world. Successful management of these pests requires thorough sampling protocols and subsequent decision-making, often based on predictive population models or expert system analysis. Incorporation of chronological age-structure of the pest population in these models, will improve our knowledge of the dynamics of these populations, including their rates of growth, behavior of their individuals, and effectiveness of control programs. There are a number of techniques that determine chronological age, however, we developed a new method based on near infrared spectroscopy (NIRS). This technique, which is easy to use, fast, and requires little sample preparation, will be useful in improving the accuracy of simulation models used to manage these species. These more accurate models will improve the effectiveness of integrated pest management programs for stored grain.

Technical Abstract: The accuracy of near-infrared spectroscopy (NIRS) for predicting the chronological age of adults of the rice weevil, Sitophilus oryzae (L.), the lesser grain borer, Rhyzopertha dominica (F.), and the red flour beetle, Tribolium castaneum (Herbst), three pests of stored grain, was examined. NIRS-predicted age correlated well with actual age of these three species. Age predictions in S. oryzae using the NIRS method are not dependent upon adult sex or temperatures to which adult weevils are exposed. Results indicated that water content decreased with increasing age in rice weevil adults, and excluding wavelengths at which water absorbs NIR radiation reduced the accuracy of correct classification. Additionally, removing cuticular lipids from insects resulted in a significant decrease in classification accuracy of weevils indicating that these compounds may be partly responsible for the ability of NIRS to differentiate young from old beetles. NIRS is a non-destructive technique that can be used to age-grade large numbers of adult stored-product beetles, information that could help to increase the accuracy of population models for these pest species.