Effects of Food Bait and Trap Type on Captures of Rhynchophorus palmarum (Coleoptera: Curculionidae) and Trap Bycatch in Southern California.

Rhynchophorus palmarum (L.) is an invasive pest responsible for killing thousands of ornamental Canary Islands date palms (Phoenix canariensis Chabaud) in San Diego County, CA. Two field experiments were conducted to compare the attractiveness of six different baits and two trap types. The tested baits were dates + water; dates + water + Saccharomyces cerevisiae; dates + water + S. bayanus; dates + water + S. pastorianus; 15% sugarcane molasses water solution mixed with 3% paraffinic oil, and a no bait control treatment. The two traps tested were white bucket traps (hanging 1.5 m above the ground and set on the ground) and black cone shaped Picusan traps (set on ground only). All traps were loaded with commercially available R. palmarum aggregation pheromone and the synergist ethyl acetate. Differences in weevil capture rates were observed across bait and trap types. Weevil captures were almost five times greater in Picusan traps compared to bucket traps that were hanging or placed on the ground. Adding dates and water alone or combined with S. cerevisiae to traps increased weevil captures compared to other baits and controls. Trap and bait types affected bycatch of nontarget arthropod species. In general, spiders, earwigs, and carabid beetles were most commonly recovered from Picusan traps, regardless of bait type. Scarab beetles, moths, and flies were found more frequently in bucket traps baited with molasses or dates mixed with S. bayanus. No effects of bait and trap type were associated with bycatch species richness.