Codling moth damage in the Hood River Valley has increased over the past several years causing major concern and economic loss to pear growers. Several factors may be responsible for the increases in codling moth damage including resistance development, incorrect timing of sprays and the switch from organophosphate (OP) insecticides to more selective, but possibly less effective control alternatives. As elsewhere, the OP insecticide Guthion (azinphosmethyl) was for many years the principal codling moth control used by pear growers. Codling moth populations in the Hood River Valley were last monitored for Guthion resistance in 1993 when no resistance was found. In 2004, the question of Guthion resistance was revisited. Orchards with potential resistance problems were identified by analyzing pheromone trap catches from several hundred trap locations. First generation codling moth males were collected with pheromone traps and tested for resistance by treating them with different concentrations of azinphosmethyl. Guthion resistance was detected in several orchards with high moth catches. In addition, diapausing codling moth larvae will be collected in orchards with poor control during the 2004 season and will be tested for OP resistance and possible cross resistance to new insecticide chemistries. In addition, the question of incorrect spray timings is being investigated. Recent shifts in codling moth flight patterns suggest that currently used predictive models may not accurately reflect codling moth phenology. The effectiveness of different control programs are being analyzed by closely examining spray records and pack outs provided by packinghouses from the last three years.