Trapping Sweetpotato Weevil, Cylas formicarius (Coleoptera: Brentidae), with High Doses of Sex Pheromone: Catch Enhancement and Weathering Rate in Hawaii

McQuate, Grant T.
Sylva, Charmaine D.
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Hawaiian Entomological Society
Sweetpotato, Ipomoea batatas (L.) Lamarck, one of the top ten staple crops produced worldwide, has increased in production in Hawaii in recent years. The sweetpotato weevil, Cylas formicarius (Summers) (Coleoptera: Brentidae), is a major economic and quarantine pest of sweetpotato in Hawaii as well as a pest of concern in all parts of the tropics where sweetpotatoes are grown. Sweetpotato weevil infestation can reduce marketable root yield as well as reduce root quality by inducing production of bitter tasting sesquiterpines by the sweetpotato tissue. Traps baited with a male sweetpotato weevil lure, (Z)-3-dodecenyl (E)-2-butenoate, can be used for population monitoring, or even for population suppression if mass trapping is done using high doses of this lure. Weathering rates, though, have not been documented in Hawaii for the higher septa loadings (100 to 1000 μg [=1.0 mg]) that have been proposed for use in population suppression efforts through mass trapping. Here, we present comparative catch rates and weathering rates, along the Hamakua Coast of Hawaii island, of traps baited with septa loaded with 12 μg, 120 μg, or 1.0 mg of male sweetpotato weevil lure. Traps baited with fresh 1.0 mg male lure caught over 22 times as many weevils as traps baited with 12 μg lure over an initial one-week trapping period. Based on a fitted decay curve, decline in attractiveness of the 1.0 mg treatment to 50% of fresh attractiveness occurred at 19.0 weeks, while the 120 μg treatment showed a 50% decline after 16.3 weeks, under climate conditions on the Hamakua Coast of Hawaii island. Further research is needed to test the effectiveness of mass trapping in reducing root damage by sweetpotato weevil, through the use of a high dose male lure in combination with the recently reported enhancement of trap catch by adding a green light source.
Ipomoea batatas, Cylas formicarius, detection, monitoring, mass trapping
Proceedings of the Hawaiian Entomological Society, 2014, 59-69.
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