results that the observed 

 patterns of pest mite and 

 A fallacis abundance 

 were entirely the prod- 

 uct of A fallacis that we 

 had released. These pat- 

 terns may have been af- 

 fected in a substantial 

 way by natural popula- 

 tions of resident or 

 immigrating A fallacis. 

 Results from the second- 

 stage and first-stage IPM 

 blocks in the 6 orchards 

 where predators were 

 not released (Table 3) 

 suggest that resident or 

 immigrant A fallacis in 

 these blocks provided 

 little pest mite suppres- 

 sion in 1988 (average 

 ratios of pest mite to A 

 fallacis frequencies after 

 June were 38:1 and 18:1, 

 respectively) but pro- 

 vided good suppression 

 in 1989 (average ratios of 

 pest mite to A fallacis 

 frequencies after June 

 were 5:1 and 6:1, respec- 

 tively). Thus, the 1988 

 ratios in these blocks 

 where predators were 

 not released were con- 

 siderably less favorable 

 for biological control 

 than the 1988 ratios in 

 blocks where A fallacis 

 were released (Tables 1 



and 2). On the other hand, in 1989 there was little dif- 

 ference in prey to predator ratio between blocks where 

 predators were or were not released in 1989. 



Table 4 provides information on possible move- 

 mentof A fallacis from trees under orupon which they 

 were released, to trees immediately adjacent where 

 predators had not been released. For this purpose, we 

 combined data across both block types and across all 

 orchards where releases occurred that year. The 

 combined data for 1988 and 1989 indicate that about 

 2.2 times more A fallacis were present on the release 

 trees than on adjacent non-release trees in July, 1.4 

 times more in August, and 1.3 times more in Septem- 

 ber. This suggests that released A fallacis may have 

 moved in substantial numbers to neighboring trees a 



month or so after release. However, this suggestion is 

 based on the questionable assumption that the major- 

 ity of A fallacis observed were ones that had been 

 released (or their progeny) and were not of wild origin. 



Conclusions 



Can any firm conclusions be drawn from our find- 

 ings to date? Unfortunately, the answer is no. There is 

 simply no way to be certain that all or even some of the 

 A fallacis we observed on sampled apple leaves origi- 

 nated from releases of A fallacis and were not of wild 

 origin. Our conclusions, therefore, are highly tentative 

 and are based on the assumption that the majority of A 

 fallacis were in fact of released origin. 



Fruit Notes, Winter, 1990 



15 



