- 7 - 



3 iol og ical Costs . There exist numerous reports in the literature that 

 season-long use of SP's results in large buildups of spider mites on apples. 

 Does even a single pre-bloom application of SP have any effect on mite popu- 

 lations? To help answer this question, in 1985 we collected data in 3^* 

 Massachusetts orchards, some of which had never used a SP and others of 

 which used a single pre-bloom SP (usually Pounce^) for 1 or 2 years. All the 

 orchards had used a pre-bloom oil spray. 



No. of No. of dosage equivalents- 

 SP h i story orc h ards of miticide used in 1985 



None used 9 1 .20 



1 year (198^4 or 1985) 12 2.03 



2 years (I98A, I985) ^ 3.l8 

 2 years (1983, 1984) 7 2.71 



*One dosage equivalent equals actual amount of pesticide used divided by the 

 amount currently recommended in the Pest Control Guide. Generally, miti- 

 cide was applied only when mites reached moderate population levels (5 or 

 more per leaf ) . 



These data indicate that, compared with orchards where a SP had never 

 been used, 70^ more miticide was applied in orchards where SP's were used 

 once (198^ or 1985), 166? more miticide where SP's were used both in 1984 

 and 1985, and 126^ more miticide where SP's were used in 1983 and 1934 but 

 not in 1985. Data of this sort are merely non-experimental, correlation- 

 type data. They cannot be taken to imply that SP usage caused mite buildup 

 without additional data from actual experiments. 



Very recently, Bostonian and Belanger (1) published a series of tests 

 where they made a single petal Fall application (recommended field rate) of 

 several types of SP's to apple trees in Quebec and measured the actual 

 amount of SP remaining after several weeks as well as the residual toxicity 

 to Amb 1 yse i us fa 1 lac i s , the major predator of spider mites in Massachusetts 

 and Quebec. Bostonian and Belanger found that 6 weeks after the single 

 treatment at pink, \2% of the original amount of permethrin and 1 8^ of the 

 original amount of fenvalerate still remained on the foliage. When they 

 confined A. fallacis predators on such foliage (6 weeks after treatment), 

 62% of the predators on permethrin leaves and 85% of those on fenvalerate 

 leaves died after 1 day, while only 6% of predators on unsprayed leaves 

 di ed. 



These findings of Bostonian and Belanger on the very long residual life 

 of SP's and the very high toxicity to mite predators probably constitute, in 

 our opinion, strong experimental evidence that SP application was the cause 

 of greater miticide use in 1985 in orchards in Massachusetts that had used 

 SP's for one or more years. 



The effects of SP's on A. fa 1 laci s in orchards are probably even more 

 devastating than Bostonian and Belanger's data reveal. On several occasions 

 we have measured spray droplet distribution on apple tree foliage and on the 

 ground cover beneath trees. At pink, massive numbers of spray droplets from 



