Pheromone Trap Monitoring System for Sweetpotato Weevil (Coleoptera: Apionidae) in the Southern United States: Effects of Lure Type, Age, and Duration in Storage

Abstract

Studies were conducted to develop a pheromone trap monitoring system for the sweetpotato weevil, Cylas formicarius (F.), in sweet potato, Ipomoea batatas (L.) Lam., in the southern United States. The current studies examined the effects of lure type, age, and their duration in cold storage on weevil collections in traps. We also characterized release rates of pheromone off soxhlet-extracted and nonextracted rubber septa. Most commercially prepared (matrix sheet system) lures and methylene chloride-extracted rubber septa did not differ in their attractiveness to C. formicarius when loaded with 10 μg of pheromone, but they did differ when loaded with 100 μg of pheromone. Traps baited with extracted rubber septa caught more weevils than those baited with matrix sheet lures. In another experiment, weevil counts did not differ among traps baited with rubber septa that were soxhlet-extracted with methylene chloride and those not extracted for septa obtained from two commercial suppliers. Regression parameter estimates from log10 release rate (ng/h) on log10 dosage did not differ among soxhlet-extracted and non extracted rubber septa obtained from one of the suppliers and extracted septa obtained from the other supplier. Lure age, however, did affect attractiveness to C. formicarius . The percentage of weevils caught per night decreased with an increase in lure age for ages between 0 and 80 d. However, nonextracted lures from one of the suppliers can probably be used for monitoring for at least 2 mo in the fleld. Soxhlet-extracted lures from the other supplier lost their attractiveness more rapidly; hence, a shorter replacement time of between 1 and 2 mo is probably sufficient. Time in cold storage did not affect the attractiveness of soxhletextracted rubber septa. Septa loaded with 10 μg of synthetic sex pheromone, sealed in air tight vials and stored in a refrigerator at 5 ± 1°C for >2.2 yr, were as attractive as those stored for only 90 d. The importance of these data in a pheromone trap monitoring program for this weevil is discussed.