ECOLOGY, SAMPLING, AND MODELING OF INSECT PESTS OF STORED GRAIN, PROCESSING FACILITIES, AND WAREHOUSES
Location: Stored Product Insect Research Unit
Title: Insect Fragments in Flour: Relationship to Lesser Grain Borer (Coleoptera: Bostrichidae) Infestation Level in Wheat and Rapid Detection Using Near-Infrared Spectroscopy
Submitted to: Meeting Proceedings
Publication Type: Proceedings
Publication Acceptance Date: November 8, 2005
Publication Date: January 31, 2007
Citation: Throne, J.E., Perez-Mendoza, J., Maghirang, E.B., Dowell, F.E., Baker, J.E. 2007. Insect fragments in flour: relationship to lesser grain borer (Coleoptera: Bostrichidae) infestation level in wheat and rapid detection using near-infrared spectroscopy. Integrated Protection of Stored Products IOBC/wprs Bulletin 30: 99-109.
The grain milling industry routinely checks wheat flour for insect fragments to determine whether the number found is below the U.S. Food and Drug Administration (FDA) defect action level of 75 fragments/50 g flour. However, the standard chemical extraction method used to detect insect fragments in flour is costly and time-consuming; thus, a rapid detection method is desirable. In addition, little is known about differences in the number of fragments produced from different stages of different insect species. In this study, we determined that wheat infested with a single pre-emergent adult lesser grain borer, Rhyzopertha dominica (F.), contributed 28 times and 10 times as many fragments as wheat infested with a single larva or pupa, respectively. Using regression models that we developed from these data, we predicted that 1-kg samples of wheat with more than 20 kernels infested with pre-emergent adult borers would be above the FDA defect action level for insect fragments. Similarly, it would take an infestation level of 380-640 kernels (in a 1-kg sample) containing larvae or pupae to exceed the defect action level. We also determined the accuracy and sensitivity of near-infrared spectroscopy (NIRS) for detecting insect fragments in flour using three different NIR spectrometers. The number of insect fragments predicted by NIRS was correlated with the actual number of fragments in test samples. NIRS was less precise than the standard flotation method, but it has the advantages that it is rapid, non-destructive, does not require extensive sample preparation, and can be automated for a more sophisticated sampling protocol for flour.