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SYNTHETIC PYRETHROIDS: BENEFITS VERSUS BIOLOGICAL 

 COSTS IN FRUIT MANAGEMENT 



Ronald J. Prokopy and William M. Col i 

 Department of Entomology 

 University of Masachusetts 



and 



Glenn E. Morin and Robin Spitko 

 New England Fruit Consultants 



Synthetic pyrethorids (SP's) were first registered for use against 

 insects in commercial apple orchards in I983. SP's include such materials 

 as Pydrin" ( fenval erate) , Ambush^ or Pounce^ (permethr i n, ) and Pay-Off 

 ( f 1 ucythr inate) . We now have 3 years of experience with commercial use of 

 SP's in Massachusetts. Here, we outline what we feel are some of the poten- 

 tial benefits of using SP's for pest control and some of the biological 

 costs that call into question the value of using SP's. 



Benef i t s. Per ounce of active ingredient, SP's are far less toxic to 

 humans than any other class of insecticides currently used in orchards. 

 Moreover, the recommended dosage of active SP ingredient per acre is much 

 less than that for other sorts of insecticides. Together, these 2 facts 

 argue in favor of SP's as potentially being of real positive value in an 

 orchard spray program. 



The primary use of SP's on apples has been as a single pre-bloom appli- 

 cation against tarnished plant bug and leafminer adults. In some orchards, 

 SP's have also been used at petal fall against plant bug and leafminer 

 adults as well as against plum curcu! io and green fruitworm. 



How effective have SP's been against their primary targets, plant bugs 

 and leafminers? A compilation of results of tests conducted in 

 Massachusetts, New York, and Maine from 198l to 1985 shows that single 

 application of SP at the optimum time (tight cluster to early pink) usually 

 reduces plant bug injury to fruit by about 70%. A similarly timed spray of 

 Guthion" or Imidan" usually reduces plant bug injury by about 50%. Several 

 exceptions to this general pattern have occurred, however, resulting in only 

 20-30% reductions in plant bug injury through SP application. These tests 

 have also shown that a tight cluster or early pink spray of SP usually pro- 

 vides season-long control of leafminer adults. Again, however, there have 

 been exceptions, particularly where leafminer adult emergence has occurred 

 over a prolonged period, beyond the duration of SP effectiveness. 



In sum, a single, properly timed pre-bloom application of SP offers a 

 method safe to humans for achieving reasonable season-long control of both 

 plant bugs and leafminers in many situations, though effective control is 

 not guaranteed. There is no other single type of material that is as effec- 

 tive against both plant bugs and leafminers as a SP. 



