Damage of Rough and Brown Rice by Four Stored-product Insect Species

Abstract

Rough rice (175 g) and brown rice (145 g) of cv. Nankin 11, ca. 6,500 kernels, were artificially infested with Ephestia cautella (Walker), Tribolium castaneum (Herbst), Rhyzopertha dominica (Fabricius), and Sitophilus oryzae (L.) at 30°C and 65% r.h. to assess losses over a 14 week period. Uninfested controls of each type of rice were also examined both at 30°C and 65% r.h. and at 10°C and 70% r.h. The variables measured were insect number, moisture content, weight of 100 kernels based on 14% moisture content, and germinability. Rough rice was not substantially affected by the presence of any insect species and largely maintained its initial quality. In brown rice, all insect species increased markedly and serious damage was detected in all variables. The brown rice lost 40, 19, 14, and 10% of initial kernel weight over the 14 weeks through infestation by R. dominica, S. oryzae, T. castaneum and E. cautella, respectively. Moisture content of brown rice in the infested treatments was higher than that of the control at 30°C and 65% r.h. in most cases. The germinabilities of the infested brown rice decreased abruptly after 4 weeks, and at the end of the experiment were almost nil. Loss assessment measures and the resistance of rough rice of this variety to insect infestation were discussed. © 1987, JAPANESE SOCIETY OF APPLIED ENTOMOLOGY AND ZOOLOGY. All rights reserved.