13- 



on horizontal 

 positions within 



block of semi- 

 iameter. The in-tree 

 alfway between the 

 alfway between the 

 top, halfway between 

 ove ground, . 5 m 

 ground, 0.5 m in 

 he trunk and 1.5m 

 st leafminers (Table 



Table 3. Comparison of P. crataegella captures on 20 x 30 cm 

 horizontal red traps ( s t i cky - s i de - up ) at various positions 

 within the tree. 



Position of trap 



Average number P. crataegella per trap 



1.5m height , 



0.5 m out from trunk 



1.5m height , 

 halfway between 

 dripline and trunk 



0.5 m height , 

 halfway between 

 dripline and trunk 



1.5m height , 



0.5 m in from dripline 



0.5 m from tree top, 

 halfway between trunk 

 and outermost foliage 



161 



125 



96 

 87 



11 



In the spring of 1982, the red horizontal (sticky- side-up) 

 traps were used in 21 IPM orchard blocks in Massachusetts. The 

 traps were placed 1.5 m above the ground and ca. halfway between 

 the tree trunk and dripline. Each week, as part of the regular 

 field scouting routine, leafminer adults were counted and removed 

 from the traps, and foliage was sampled to determine the average 

 number of mines per leaf. Cumulative average trop captures were 

 highly positively correlated with the number of mines per leaf 

 in the 21 blocks sampled. Figure 1 represents a regression of 

 mines per leaf on trap captures through 2 weeks after petal fall and 

 illustrates a prediction of 0.13 mines per leaf (the first gener- 

 ation Economic Injury Level for stressed trees) at a cumulative 

 average of 12 P. crataegella per trap. 



