Submitted to: Environmental Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: October 10, 2002
Publication Date: N/A
Interpretive Summary: The sawtoothed grain beetle is an important pest of stored grain, cereal products, dried fruit and other food products. Protection of food against damage and contamination by this pest during storage, processing, and marketing has relied heavily on routine application of chemical insecticides. However, increasing concern about the health and environmental hazards of insecticide application, has made it necessary to seek new pest control methods that employ insecticides only as needed. These new methods will require pest monitoring to determine timing and location of control intervention. Effective insect traps have been developed for this purpose, but improvements are needed in lures to draw insects from machinery and other hiding places into the traps. Knowledge of directed insect movements and the factors that control them are useful in seeking these improvements. Scientists at USDA, ARS, Center for Medical, Agricultural, and Veterinary Entomology in Gainesville, Florida, determined the influence of low humidity and carbon dioxide, singly and in combination, on the movement of the sawtoothed grain beetle in response to differences in humidity. This information will be useful to researchers in developing improved lures and monitoring methods. Ultimately, it will benefit pest control operators, food processors, warehousemen, retailers, and consumers.
Technical Abstract: The spatial distribution of storage pests is of special significance in detection, monitoring, and control (precision targeting of treatments). Understanding the role of behavioral responses (oriented movements) to physical gradients in the environment is basic to understanding spatial distribution, as well as pest population dynamics and the process of infestation. The behavioral response of the sawtoothed grain beetle, Oryzaephilus surinamensis (L.), to moisture gradients has been studied in some detail, but the effect of carbon dioxide (CO2), alone and in combination with low humidity, has never been reported. The effect of CO2 is of some interest, because CO2 levels are often elevated well above normal atmospheric levels in infested grain. The responses of adult male O. surinamensis to humidity alternatives of 60 and 100% RH were determined in two-way choice chamber after various treatments. Exposure to a dry atmosphere (<5% RH) with an elevated level of CO2 (39%) for 4 h produced a reversal from a hygronegative to a hygropositive response. The same period of exposure to dry air (<5% RH), or to a moist atmosphere (80% RH) with an elevated level of CO2 did not produce a reversal. Although some weakening of the hygropositive response was evident in both cases, the change was not statistically significant.