-12- 



large percentage o£ the apples at harvest. Most of the dimples 

 were near the calyx. Many were deep, but some were shallow and 

 surrounded by a small (1/16" - 1/4") tan-colored scab. Only a 

 small percentage o£ dimpled fruit resulted from TPB feeding from 

 green tip to early pink and from first cover or later. 



TABLE 2 



Time of initiation of injury % Dimpled fruit 



by TPB adults in cages at harvest 



Green tip to early pink 12-0 



Mid-pink to petal fall 471 



First cover or later 9% 



Check (cages without TPBs) 0?; 



The economic consequences of dimpling injury caused by TPB feed- 

 ing vary from grower to grower according to the intended market of 

 the fruit and the severity of dimpling. When you come right down 

 to it, the dimples are purely cosmetic injuries and affect only the 

 appearance of the fruit. In no way do the dimples affect the eating 

 or keeping quality of the fruit, as do injuries by apple maggot, plum 

 curculio, and codling moth. Most Massachusetts growers with whom we 

 have spoken feel they can tolerate 1-3% of lightly dimpled fruit in 

 their cartons of U.S. Fancy or better fruit. Moderately or heavily 

 dimpled fruit is usually culled. 



Our next goal was to develop a method for monitoring the abun- 

 dance of TPB adults on trees throughout the period when they could 

 cause injury: silver tip through petal fall. In many crops where 

 TPB is a pest (e.g. alfalfa, sugarbeets), TPB abundance can be readily 

 and rather accurately monitored by collecting TPB in sweeps with an 

 insect net. This method is not useful for collecting TPBs on the 

 woody twigs and branches of fruit trees, however. 



Because plant bugs are rather closely related to aphids, we 

 suspected that plant bug adults, like aphid adults, might use visual 

 cues to guide them to their host plants and feeding sites. Our 

 approach was similar to that which we used in developing a method 

 of monitoring European apple sawfly populations in apple orchards 

 (see Fruit Notes 43(1): 9-12). Using a spectrophotometer (an instru- 

 ment which records the wavelengths of light reflected from surfaces) , 

 we measured the spectral reflectance pattern of the surface of all 

 apple structures susceptible to TPB feeding injury. We also measured 

 the spectral reflectance pattern of surfaces to which we had applied 

 various enamel paints. By so doing, we were able to select particular 

 painted surfaces which closely mimicked the reflectance patterns of 



