672 INSECTS AFFECTING VEGETATION 



wheats, some of which also have a minimum of rust and have been 

 the means of opening up millions of acres to wheat culture which 

 were practically unused before. 



Orton's work with cotton, watermelon and cowpea root dis- 

 eases, so destructive in the South, is another example of practical 

 disease resistance breeding. He has found, or produced varieties 

 which will bring a crop where the ordinary kinds would fail, and in 

 case of the watermelon, the new variety is a cross with the disease 

 resistant citron melon, worthless from the watermelon standpoint, 

 yet the new form combines with resistance all the good qualities of 

 the watermelon. 



Jones, of Vermont, also has tested and selected from the great 

 variety of potatoes a number of kinds resistant to scab and blight. 

 A Colorado man has published accounts of a blight resistant canta- 

 loupe. Some of the new alfalfas introduced by the United States 

 Department of Agriculture, are proving to be only slightly attacked 

 by the leaf-spot, which is one of the worst alfalfa foes. 



A tabulation has been given in New York and Nebraska Ex- 

 periment Station Bulletins of the relation of apple varieties to scab. 

 And while they do not agree entirely, a few varieties that were found 

 resistant are given: Oldenburg, resistant in both States; wealthy, 

 resistant in Nebraska; Gano, resistant in New York. Others, as 

 Wine-sap, Northern Spy, Baldwin, Spitzenburg, &c., were very sus- 

 ceptible to scab. 



Among our trees especially susceptible to fire blight are: 

 Yellow Transparent, Maiden Blush and Fall Pippin. In fact, in 

 some orchards these varieties have been almost destroyed by this 

 disease, appearing frequently in the form of body-blight and collar- 

 rot. Varieties of apple show very noticed, difference in resistance 

 to rust. 



I have noted in our nurseries and orchards that some varieties 

 of peach of which Tilletson is a striking example, are much more 

 subject to the white mildew. Scab resistant potatoes are on the 

 market. The McCormack and other potato varieties seem more 

 or less blight resistant. The Mildew on roses varies greatly with 

 different varieties; the Rambler roses being very subject to it. The 

 Lima bean is much troubled by the downy mildew when other beans 

 are free from it. 



It seems possible, judging from variation observed in our fields, 

 that varieties of cabbage may be produced, resistant to black rot, 

 for which destructive disease no remedy is now known. This prin- 

 ciple will apply to other diseases as well. 



The foregoing will serve as examples of what is being done in 

 this line and indicate what can be done further in selecting and 

 breeding. The resistant forms now in our possession may be used 

 as the parents of still more resistant ones to be developed in the fu- 

 ture, and also for crossing with less resistant, but more productive 

 or otherwise desirable kinds to improve them. (Trans. Peninsula 

 Hort. Soc. 1908.) 



