Three Rust Diseases of the Apple 7 



the fruit is obviously considerable, a fact which, with a few exceptions 

 (Giddings, 1918, and Gardner, 1925), has escaped emphasis in the liter- 

 ature of apple rust. The varieties Baldwin, Greening, Williams, and 

 Wagener have been found free of fruit infection in orchards in which 

 both apple and quince rusts were present, at least in small amounts. 



With the varieties of apples that have been studied, the quince rust 

 causes distinctly more injury to infected fruits than does the apple rust. 

 With some varieties, a large proportion of the fruits affected by the 

 quince rust may fall from the tree before harvest time, and often the 

 remaining fruits are rendered worthless. On June 27, 1928, the fruit 

 on a Mcintosh tree showed 33 per cent infection, while 47 per cent of 

 the dropped apples under the same tree were infected. Again, on Sep- 

 tember 11, 1928, the fruit on a Delicious tree and the drops from the 

 same tree showed 51 and 97 per cent infection, respectively. 



The data in table 3 illustrate in another way, in part, the loss due to 



TABLE 3. Dropping of Rust-Infected Fruit Shown by Successive Counts on the 



Same Trees, 1928 



Variety 



Rust 



First count 



Date 



Per cent 



of infected 



fruit 



Second count 



Date 



Per cent 



of infected 



fruit 



Fameuse 



Hubbardston . . 



Mcintosh 



Mcintosh 



Mcintosh 



Mcintosh 



Mcintosh 



Mcintosh 



Jonathan 



Sutton Beauty. 

 Winter Banana 



Quince 



Quince 



Quince 



Quince 



Quince 



Quince 



Quince 



Quince 



Apple 



Apple 



Apple 



July 5 

 July 5 

 July 5 

 June 27 

 June 27 

 June 28 

 June 21 

 June 27 

 July 5 

 June 27 

 June 27 



21 

 14 

 20 

 14 

 33 

 31 

 53 

 65 

 24 

 20 

 16 



Sept. 10 



Sept, 10 



Sept. 10 



Sept. 11 



Sept. 11 



Sept. 11 



Sept. 10 



Sept. 11 



Sept. 10 



Sept. 11 



Sept. 9 



20 



28 



6 



4 



8 



16 



28 



26 



38 



27 



14 



fruit infection on several varieties. The second counts were made in 

 each case on the same tree or trees as were the first counts. A wide vari- 

 ation in the dropping of fruit is seen, even among the varieties affected 

 by the quince rust. This difference in behavior is apparently parallel 

 with the type of injury rather than with the variety of apple or the 

 species of fungus involved. The symptoms on Mcintosh and Delicious 

 fruits are distinctly necrotic in type, while those on the varieties other 

 than Mcintosh in table 3 are usually hyperplastic or hypoplastic. 



