34 N. H. AGR. EXPERIMENT STATION. [Bulletin 171 



«arly and of mellowing soon after it falls, is a factor of importance 

 in the continued infestation of that variety by the maggot. 



In Table 2 it will be seen that of the first 11 varieties in order 

 of freedom from infestation not one is early fruit. Of the last 

 10 varieties on the list, representing maximum comparative in- 

 festation, 7 are summer fruit or begin to drop early. 



Aroma. Early maturity is not, however, the only factor. 

 The aroma or flavor of the fruit is unquestionably of much in- 

 fluence in comparative attack; the varieties with sweet flesh or 

 with aromatic flavor suffering worst. 



Thus the Tolman Sweet, though a fruit of late fall, ranks toward 

 the bottom of the list. The same is true of the Pound Sweet and 

 the Nodhead. Other late varieties such as Northern Spy, Bailey 

 Sweet, Spitzenburg, Gravenstein, Grimes and King, doubtless 

 owe a certain measure of their infestation to their aroma, though 

 in part to other causes. Taking the reverse condition we find 

 that Yellow Transparent, distinctly a summer fruit, has brisk 

 subacid flesh and is often comparatively free of attack. 



Thickness of Skin. Apparently the thickness of the skin 

 is a factor, perhaps because the flies find it more difficult to punc- 

 ture, perhaps because a thick skin permits less of the aroma to 

 -escape. Of the first 12 varieties on the list in order of freedom 

 from infestation 11 have a tough or a thick skin. 



Characters in Combination. Considering the characters in 

 combination we find that fruits possessing two or three of the 

 above qualities favoring infestation are likely to rank near the 

 bottom of the list. Those which have place at the top of the list 

 are marked by possession of two or three of the reverse of these 

 characters. 



Location near Susceptible Varieties. A fourth condition 

 bringing about many reports of infestation of a variety is 

 the comparative abundance of that yariety in the average New 

 Hampshire orchard, which in turn carries with it a probability 

 that on the average farm there will be some trees of this abundant 

 variety located near susceptible early or sweet fruit. It has 

 frequently been observed in the course of our work that trees of 

 varieties not favorable to the maggot that stand close to a tree 

 of highly susceptible variety are prone to attack, especially in 

 seasons when the early tree bears sparingly or not at all. 



