butyl hexanoate consis- 

 tently captured more flies 

 than spheres baited with 

 ammonium carbonate or 

 no odor. This trend was 

 observed throughout each 

 of the five 2-week trap- 

 ping periods. Ammonium 

 carbonate was not effec- 

 tive, capturing only about 

 as many flies as the no- 

 odor treatment. In addi- 

 tion, spheres with both 

 ammonium carbonated 

 and butyl hexanoate were 

 no more effective than 

 spheres with butyl 

 hexanoate alone. A subsequent analysis of 

 captured females showed that there was no 

 difference in reproductive maturity of females 

 among odor treatments. For the most part, 

 females captured on all of the odor treatments 

 throughout the season were sexually mature (> 

 90%) and of high egg load (>20 eggs/female). 



In a previous study in an artificial orchard 

 of potted apple trees, we observed that 

 ammonium carbonate increased maggot-fly 

 captures on red spheres when used alone or 

 with butyl hexanoate. However, this was not 

 the case in commercial orchards. There are 

 several possible explanations for the ineffec- 

 tiveness of ammonium carbonate in commer- 

 cial orchards. Part of the problem may stem 

 from the design of the dispenser. Typically, 

 under the hot summer orchard conditions of 

 1995, all of the ammonium carbonate would 

 dissipate within a week of deployment, leaving 

 an empty container for the duration of the 2- 

 week period. In addition, we observed that the 

 vast majority of captured females were 

 sexually mature. Once mature, maggot flies do 

 not require as much protein as immature flies, 

 and therefore may not respond to a protein food 

 odor such as ammonium carbonate. Such 

 mature flies (with a developed egg load) are 

 more interested in finding egglaying sites, 

 which may also explain the greater number of 

 captures on spheres baited with butyl 



hexanoate. 



These findings are important for several 

 reasons. First, ammonium carbonate should 

 probably no longer be considered as a viable 

 odor attractant for use with red sticky spheres 

 in commercial orchards. Second, butyl 

 hexanoate was shown to be very effective, 

 capturing four to six times more flies than 

 unbaited spheres throughout the growing 

 season. There was some concern that later in 

 the season, ripening apples might emit enough 

 natural butyl hexanoate to mask the butyl 

 hexanoate in the lures. This, however, was not 

 observed in our study. Based on the results of 

 this work, we conclude that in commercial 

 orchards, butyl hexanoate is an excellent lure 

 for use with red sticky spheres to capture 

 maggot flies, whereas ammonium carbonate is 

 not. 



Acknowledgments 



We thank Tony Lincoln, Dave Chandler, 

 Bill Broderick, and Wayne Rice for the 

 generous use of their orchards. We also thank 

 Andy Kaknes, Eric Quist, Jen Mason, Starker 

 Wright, Jon Black, and Mike Marsello for 

 outstanding technical assistance. This work 

 was supported by USDA CSRS NRI grant 95- 

 37313-1890 Cooperative Agreement 94-COOP- 

 1-0482. 



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Fruit Notes, Volume 61 (Number 4), FaU, 1996 



