Laboratory observations. Table 2 shows that in 

 2000 (when Guthion® was evaluated), 91, 67, and 75 

 % of total PCs reached the top of unsprayed limbs, 

 pyramids, and cylinders, respectively, whereas for 

 sprayed counterparts, only 44, 0, and 25%, respectively, 

 reached the top. Table 2 also reveals that in 2001 (when 

 Imidan® was evaluated), 100, 100, and 94% of total 

 PCs reached the top of unsprayed limbs, pyramids, and 

 cylinders, respectively, whereas for sprayed 

 counterparts, only 65, 59, and 50%, respectively, 

 reached the top. Comparatively, Guthion® exerted a 

 greater negative effect than Imidan® on the propensity 

 of PCs to crawl up the structures evaluated. 



Conclusions 



Results from the 200 1 field experiment suggest that 

 when orchard trees are sprayed with Imidan® to protect 

 against PC damage, PC captures by cylmder traps are 

 strongly compromised during the first 10 days after 

 application. This suggests that, particularly during this 

 period of time, PC captures by cylinder traps would be 

 very poor indicators of PC population levels in tree 

 canopies, with a remarkably poor ability to forecast 

 PC injury to fruit. In 2001, the negative effects of 

 insecticide application were not apparent after 10 days 

 following an application of Imidan®. 



Several of our studies have shown that odor-baited 



cylinder traps, when deployed in 

 commercial orchards, offer little 

 or no value for predicdng extent 

 of PC injury to fruit, which we 

 have attributed, in part, to the 

 presence of insecticide on the trap 

 surface. As found in the 2001 

 study, even unsprayed traps failed 

 to reflect the amount of PC injury 

 to fruit located in trap-bearing or 

 adjacent trees. Such poor ability 

 could have been due then to the 

 possibility that very few PCs were 

 present on sprayed trees. Even so, 

 PC presence was sufficiently great 

 to inflict damage to fruit. 



In both 2001 and 2002, 

 unsprayed black pyramids 

 captured numerically more PCs 

 than unsprayed black cylinders, 

 which suggests that small 

 pyramids offer a stronger visual stimulus to PCs than 

 cylinders. 



Results from the laboratory observations confirmed 

 the negative effect of organophosphate insecticide 

 application on trap performance found in the 200 1 field 

 study. Here, there was strong evidence that, in the 

 absence of any odor bait, PCs are reluctant to crawl 

 upward on traps sprayed with Guthion® or Imidan®. 

 Nonetheless, tree limbs sprayed with organophosphate 

 insecticide proved considerably less deterrent to PCs, 

 possibly because tree limbs possess positive contact 

 stimuli that tend to override negative effects of 

 insecticide. 



Results from the 2002 field study, however, failed 

 to show an effect of insecticide application on trap 

 captures even when the same insecticide (Imidan®) and 

 dose (3/4 pound per 1 00 gallons water) was utilized as 

 in the 2001 study. This may be due to the fact that the 

 amount of benzaldehyde used to bait traps in 2002 was 

 four times greater than in 2001 (2.5 mg/day vs. 10 mg/ 

 day in 2001 and 2002, respectively). Therefore, in 2002 

 PCs may have been more strongly drawn to enter the 

 trap tops, overcoming the negative effect of insecticide. 

 Combined results suggest that, in the absence of 

 any odor (as in our lab study), PCs are substanfially 

 repelled from climbing up organophosphate-sprayed 

 traps. However, such negative effect seems to be less 

 pronounced as the amount of odor bait (i.e. 



Fruit Notes, Volume 67, Fall, 2002 



11 



