We were unable to draw strong conclusions 

 from data on pre-bloom visual trap capture of 

 adults vs. mines per leaf (Figure 2), largely 

 because of high variability of mine numbers at 

 low trap capture levels. Without exception, 

 however, growers who had moderate or high 

 numbers of leafminers per trap (three per trap 

 by tight cluster and nine per trap by pink) were 

 over the threshold of 13 mines per leaf in the first 

 summer generation. Unfortunately, at low trap 

 capture numbers (average of zero to less than 

 nine per trap), the correlations did not hold up 

 well. In some cases, low captures on trunk and 

 canopy traps coincided with the expected low 

 number of mines, but in other cases they led to 

 mine numbers that were well over the thresh- 



old. In a few cases, orchards which had no adults 

 caught on traps had potentially damaging levels 

 of first-generation mines. Some growers who 

 were not part of our second-level IPM program 

 also reported low trap captures followed by over- 

 the-threshold mine counts. In Figure 2, note 

 that for both trunk and canopy traps, the rela- 

 tionship between the numbers of captured 

 adults and the numbers of mines in leaves was 

 not significant. 



Oddly enough, these data are opposite to the 

 trend found in 1990, when, possibly due to 

 unfavorable conditions during leafminer flight, 

 high trap captures were followed by a low num- 

 ber of first-generation mines. It is not clear why 

 the pattern in 1991 was unusual. One possible 



18 



Fruit Notes, Spring, 1992 



