20 

 TIMING THE TARNISHED PLANT BUG: A TALE OF FRUSTRATION 



Ronald J. Prokopy, Susan L. Butkewich, and Thomas A. Green 



Department of Entomology 



University of Massachusetts 



In 1976 we began what turned out to be 11 consecutive years of research on 

 (a) the stages of plant development during which tarnished plant bug (TPB) 

 injury to apple is initiated, (b) the most efficient method of monitoring the 

 appearance of plant bug adults, and (c) the efficacy of various pesticides for 

 controlling plant bugs. In 4 previous issues of Fruit Notes [43(2) : 10-14, 

 44(2) :l-5, 45(3):15-18, and 45(4)13-14], we reported our results of the first 4 

 years. In brief, we found that (a) apple flower buds, blossoms, and developing 

 fruit are susceptible to TPB feeding injury from silver tip to about one month 

 after petal fall, (b) susceptibility to bud abortion (abscission) is greatest 

 from silver tip until tight cluster, while susceptibility to fruit injury 

 (dimples and/or scabbing) is greatest from tight cluster to a month after petal 

 fall, (c) a 6 X 8 inch sticky white rectangle trap placed at knee height near 

 the periphery of the tree offers an effective method of monitoring the 

 abundance of TPB adults, (d) capture of 2.5 or more adults per trap from silver 

 tip through tight cluster or 4.2 per trap from silver tip through midpink 

 indicates an economically justifiable need for treating TPB adults with 

 pesticide, and (e) no given type of pesticide guarantees a high degree of TPB 

 control, though Cygon" may be the most effective material, followed by various 

 synthetic pyrethroids, Guthion", Imidan", and Lorsban" or Thiodan'", in that 

 order. 



One major question that emerged from the first 4 years of work was: how 

 can one predict the best time to apply a pesticide against TPB? In other 

 words, could one piece together knowledge of the time of greatest 

 susceptibility of developing blossoms and fruit to TPB injury with knowledge of 

 the time of greatest abundance of TPB adults in the orchard and determine a 

 time at which pesticide application should be the most effective? For the past 

 6 years (1981-1986), we have attempted to answer this question through research 

 at the Horticultural Research Center in Belchertown, MA. 



Methods 



To gain information on the time at which fruit injury was initiated in an 

 unsprayed block, we placed cloth bags over branch terminals harboring 

 developing flower buds to exclude TPB adults for specified time periods. For 

 the first 3 years (1981-1983), we used 2 approaches to bagging buds. In the 

 first experiment, we employed 280 bags (half on Mcintosh, half on Delicious) at 

 silver tip. At each of 6 stages (tight cluster, early pink, late pink, petal 

 fall, 1 week after petal fall, 2 weeks after petal fall), we removed 40 bags 

 (20 per cultivar), thereby exposing the buds to TPB from time of bag removal 

 onward. Check bags remained in place the entire season. In the second 

 experiment, no terminals were bagged until tight cluster. At that time and at 

 each of the above stages thereafter, we bagged 40 terminals (half on Mcintosh, 

 half on Delicious), thereby preventing TPB from causing injury from time of 

 bagging onward. Check terminals remained unbagged the entire season. In both 



