Table 1 . Calcxilating the trap-capture thresholds for tarnished plant bug (TPB) and European apple 

 sawfly (EAS) in retail and wholesale apple orchards. 



I. The "break-even" level of injury is calculated related to the cost of the injury and the 

 cost of the treatment. 



E + L + C 



B = 



where: 



(P)P(F/100)[$XF-($NO)(NO/100)-($U)(U/100)-($P)(P/100)] 



B = "Break-even" proportion of injury 



E = Equipment cost per acre 



L = Labor costs per acre 



C = Chemical costs per acre 



P = Total production per acre 



XF = % U. S. Extra Fancy if no injun/ was to occur 



$XF = Value of 1 bushel of U. S. Extra Fancy grade fruit 



$NO = Value of 1 bushel of U. S. Number 1 grade fruit 



NO = % of injured fruit downgraded to U. S. Number 1 grade 



$U = Value of 1 bushel of Utility grade fruit 



U = % of injured fruit downgraded to Utility grade 



$P = Value of 1 bushel of Processing grade fruit 



P = % of injured fruit downgraded to Processing grade 



The following calculations were made with the assumptions used in this article. 



For TPB in a retail operation: 



B(retail-TPB) = 



$2.17 + $1.75 + $8.55 



(500 bu)(80%/100)[$15 - ($9)(20%/100) - ($7.50)(70%/100) - ($2)(10%/100)} 



= 0.004 = 0.4 % 



Fruit Notes, Spring, 1989 



