Submitted to: Journal of Stored Products Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 31, 2001
Publication Date: N/A
Interpretive Summary: Feeding bioassays are an important component in understanding feeding patterns and food preference among insect pests. The small size of stored-product insect pests and the cryptic tendencies of these insects make feeding studies difficult. An encapsulation method has been developed to produce liquid and semiliquid diets for rearing beneficial insects. A scientist at the Center for Medical, Agricultural and Veterinary Entomology, ARS, USDA in Gainesville, Florida, conducted research to determine if this method could be used to encapsulate dry food for use in feeding studies of stored product beetles. Washed sand and ground dog food were encapsulated and were used in tests with adults of the red flour beetle, the sawtoothed grain beetle and the rice weevil. There was little or no feeding activity observed in tests with encapsulated sand pellets. The stored product beetles quickly chewed into the encapsulated dog food pellets, and feeding activity was quantified by the amount of food observed to be scattered around the base of the pellet. Rice weevils responded very quickly and the entire pellet was essentially consumed within the first 4-5 h of the study. Red flour beetles responded the most slowly, although overall response was similar to sawtoothed grain beetle feeding in the first 24 h. Encapsulated diets provide a promising method to evaluate feeding behavior of stored product beetles. Alternate substrates could be encapsulated to measure insect response, and attraction or repellence could be tested by adding test substances to the material being encapsulated or added to filter paper placed under an encapsulated pellet. Results will be useful in tests attractants to be used in traps or for studying potential repellents.
Technical Abstract: A procedure that was developed to encapsulate liquid and semiliquid diets was used to encapsulate dry diet for use in a feeding bioassay for beetles that are pests of stored products. Vacuum was used to deform Parafilm into numerous 6 mm diam. wells. The wells were filled with clean sand (control) or ground dry dog food (test), and the Parafilm sealed to produce individual pellets. A single pellet was then placed in the center of a 9 cm diam. Petri dish and feeding activity of groups of ten adults of Sitophilus oryzae (L.), Oryzaephilus surinamensis (L.), and Tribolium castaneum (Herbst) was tested. Number of insects on the encapsulated pellet and amount of food or sand scattered were checked hourly for the first 8 h of the study and after 24 h. Few insects were observed on pellets containing sand and little or no sand was observed scattered outside of the pellet, so presence of dog food in the pellet was needed for insects to feed on the pellet. In tests with encapsulated dog food, amount of food scattered provided a better quantitative measure of feeding than number of insects on the pellet. Insects starved for 48 h caused greater amounts of food scatter than insects starved for 24 h prior to the test. In direct comparisons among all three species, T. castaneum responded the most slowly and the bioassay may be improved by increasing the amount of time starved. S. oryzae responded very quickly and the entire pellet was essentially consumed within the first 4-5 h of the study. It was found that the encapsulated diets provide a promising method to evaluate feeding behavior of these stored product insect pests.