THE PLUM CURCULIO IN APPLES 



27 



In general, smooth skinned fruits are preferred, and in a mixed orchard 

 cherries, prunes, apricots, and nectarines are heavily attacked. Feeding occurs 

 on pears but the grubs do not develop in them. There are also records of 

 unimportant feeding on grapes, huckleberries, and persimmons. 



The preference of the curculio among commercial fruits of Massachusetts 

 is indicated by the following record: 



Table I. — Number of Punctures in Different Fruits Made by 20 Plum 



Curculio Beetles Confined in Breeding Cages for 



14 days. June 2 to 15, 1928. 



Plum Apple Cherry Pear Peach 



Eg-g- punctures 105 100 15 3 2 



Feeding punctures 156 153 206 58 30 



Total 261 253 221 61 32 



Preference Among Apple Varieties. 



All varieties of apples are attacked but those which blossom early and 

 grow most rapidly after the petals fall are the first to provide attractive 

 food and suitable locations for eggs, and consequently are the most severely 

 injured. Among such_ varieties in Massachusetts are Duchess (Oldenburg), 

 Yellow Transparent, and Gravenstein. Baldwin suffers moderate to severe 

 injury, but Mcintosh is less severely attacked than other commercial apples. 



The rate of growth early in the season of five varieties, indicating their 

 potential susceptibility to curculio injury, is shown by the following 

 measurements of ten apples each in 1928, and offers a basis for comparison 

 with other varieties. A larger number of measurements and a variety of 

 growing conditions may change these figures considerably, but many field 

 observations lead the writer to believe that the comparisons are substantially 

 correct. 



Table 2.— Rate of Growth of Apples. Waltham, Mass. 



The potential susceptibility to curculio injury of the New England Seven 

 (3) may be listed from greatest to least as follows: Gravenstein, Baldwin, 

 Delicious', Wealthy, Northern Spy, Rhode Island Greening, and Mcintosh. 



Feeding activities during the summer and fall are concentrated on the early 

 maturing varieties especially if they are allowed to become mellow on the 

 tree, and more larvae develop to maturity in summer and fall apples than in 

 winter apples. 



The number of curculios collected on apple trees of different varieties 

 indicates the choice of beetles, and in the following table the comparison 

 of Delicious and Baldwin includes suflScient trees to be significant. 



Delicious appears to be more deformed by curculio injury than Graven- 

 stein or Baldwin. 



