Defining sources of coffee plant odor attractive to Ceratitis capitata flies

We evaluated attraction of released mature laboratory-cultured Mediterranean fruit flies to different sources of coffee plant odor placed in potted nonfruiting guava trees in outdoor field cages. Volatiles from crushed medium or dark red fruit of Coffea arabica cv. arabica plants were significantly more attractive than volatiles from cut leaves or stems of such plants, volatiles from less-ripe crushed C. arabica fruit, and volatiles from crushed red fruit of C. racemosa, C. canephora, or C. dewevari. Volatiles from C. arabica cv. arabica crushed red fruit were equally attractive as volatiles from crushed red fruit of C. congensis or C. arabica cv. mundo, cv. bourbon, cv. kents or cv. catura. Volatiles from as little as 2 g of crushed red C. arabica fruit (= 1 fruit) were as attractive as volatiles from 32 g of such fruit, demonstrating sensitivity of the bioassay approach used to a small amount of source material. Odor of C. arabica red fruit refrigerated for 1-10 days after picking was significantly more attractive than odor of fresh-picked fruit, while odor of a 24-hr water extract of intact red C. arabica fruit was significantly more attractive than odor of 24-hr extracts of such fruit with methanol, methylene chloride, or hexane or 1- or 6-hr extracts with water. Extraction studies suggested that at least some of the volatiles of red coffee fruit attractive to medflies may be polar water-soluble molecules. In our final test, volatiles from crushed red C. arabica fruit trapped on Super Q and eluted with methylene chloride proved just as attractive as volatiles emanating directly from crushed fruit of the same type. Together, our findings define optimal source material and effective handling procedures of source material for future identification of volatile components of coffee fruit attractive to medflies.