as in the first generation where data were available (B, 

 C, E, J). Thus, with the exception of Orchard D, data 

 indicate that the leafminer species that dominated in 

 the first generation remained dominant in the second 

 and third generations. 



To faciHtate comparisons, the 16 orchards were 

 categorized into four groups (Table 3). Data in Table 

 3 show that for abandoned orchards M, N, O, and P, all 

 of which were dominated by STLM and none of which 

 received insecticide in 1999, LM population density 

 decreased (on average) by more than half from the first 

 to the third leafminer generation. In contrast, for 

 commercial orchard F, likewise dominated by STLM 

 and likewise having received no insecticide treatment 

 against LM in 1999, LM population density increased 

 89-fold from the first to the third leafminer generation. 

 In commercial orchards A, D, G, and I, also dominated 

 by STLM but having received an insecticide treatment 



against LM in May of 1999, LM 

 population density increased by an average 

 of about two-fold from the first to the third 

 leafminer generation. Finally, in 

 commercial orchards B, C, E, H, J, K, and 

 L, dominated by ABLM and having 

 received an insecticide treatment against 

 LM in May of 1999, LM population 

 density increased by an average of about 

 five-fold from the first to the third 

 leafminer generation. 



For all four categories of orchards, 

 parasitism by S. maiylandensis decreased 

 progressively from the first to the third LM 

 generation, averaging (across all 

 generations) 36% for abandoned orchards, 

 26% for commercial orchards dominated 

 by STLM and treated against LM in 1 999, 

 and 18% for commercial orchards 

 dominated by ABLM. Parasitism by P. 

 ornigis across all three generations 

 averaged 1 1 % for abandoned orchards, 9% 

 for commercial orchards dominated by 

 STLM and treated against LM in 1999, 

 and 2% for commercial orchards 

 dominated by ABLM, with no consistent 

 trend toward increasing or decreasing 

 abundance across generations. 



Together, data in Table 3 suggest that 

 the high amount of total parasitism of LM 

 (47%) in the abandoned orchards may 

 have been a principal factor associated with the 

 decrease rather than an increase in LM population 

 density from the first to the third LM generation. The 

 level of total parasitism in Orchard F was only about 

 one-third that in the abandoned orchards and was 

 insufficient to prevent the 89-fold increase in LM 

 population density from the first to the third generation. 

 The substantially greater amount of total parasitism 

 (35%) m STLM-dominated orchards treated against 

 LM in 1999 than total parasitism (20%) in ABLM- 

 dominated orchards treated against LM m 1999 may 

 have played a role in the lower rate of first-to-third- 

 generation LM population growth in the former (two- 

 fold) compared with the latter (five-fold). 



Finally, the data m Table 3 indicate that P. ornigis 

 parasitoids were considerably more abundant in 

 abandoned as well as LM-treated orchards dominated 

 by STLM than in LM-treated orchards dominated by 



Fruit Notes, Volume 67, Summer, 2002 



15 



