You could be purchasing fruit with higher pesticide residues.
Peach growers outside California battle an extremely destructive and difficult to control pest, called Plum Curculio. Infestations of this pest result in wormy fruit and can be controlled only by a strict pest management program consisting of heavy applications of prophylactic pesticide. Sprays for Plum Curculio begin at petal fall and continue into the harvest season. The use of pheromone blockers, which are commonly used in California as an “all-natural” way to fight off invasive pests, have no effect on the Plum Curculio.
The California tree fruit industry has dedicated years of research into finding solutions to lower pesticide use. Today California farmers have incorporated very strict pest management programs to comply with over 70 California laws and regulations. In 2008 Priums Labs conducted residue tests on California peaches, plums and nectarines using the same procedures as those employed for gathering PDP data by the USDA. There were large number of samples with no detectable insecticide residues and those that were found are far below the allowable limits.
Brannen, Phil. 2010 SOUTHEASTERN PEACH, NECTARINE AND PLUM PEST MANAGEMENT AND CULTURE GUIDE. January 2010. February 2011 <http://www.ent.uga.edu/peach/PeachGuide.pdf>.
California Tree Fruit Agreement. http://www.eatcaliforniafruit.com/ppn/media/pr_detail.asp. 14 August 2009. 15 February 2010 <http://www.eatcaliforniafruit.com/ppn/media/pr_Detail.asp?prID=102>.
Horton, Dan. Developing Novel IPM Strategies against Plum Curculio. 9 February 2009. 15 February 2010 <http://www.clemson.edu/ipm/reports/04parker.pdf>.
Howitt, Angus H. Plum Curculio. 10 September 1997. 1 June 2010 <http://www.canr.msu.edu/vanburen/plumcurc.htm>.
Lan, Z. Reduced Midseason Pesticide Program for Control of Scab and Plum Curculio in Peach. June 2003. 15 February 2010 <http://apsjournals.apsnet.org/doi/pdf/10.1094/PDIS.2003.87.6.699>.
Primus Labs. 2008 Primus California Residue Study. 10 October 2008. <http://www.eatcaliforniafruit.com/ppn/pdfs/growers_shippers/meetings/543RSC_Minutes_092508_FINAL.pdf>.