NOTES ON PLANT DISEASES OF CONNECTICUT. 72 I 



Diseased, but 



Date of not marked Not 



Examination in 1908 Dead Improved Improved Cured Total 



July, 1909 24 5 54 38 21 142 



Nov., 1910 18 6 9 65 44 142 



This shows that there has been gradual improvement since 

 the trouble first showed in 1907, and that there has been practi- 

 cally no subsequent spreading of the trouble. That is, in 1910 

 there were only eighteen trees showing the disease, among the 

 3,000 to 3,200 in the plot, that did not show it in the spring of 

 1908. Of these eighteen, at least thirteen were included as 

 questionable; that is, there was not positive evidence that it 

 was this trouble, as the leaves were only slightly affected. No 

 doubt, too, some of these were trees that were not marked 

 originally because they were not badly injured. It is also quite 

 probable that some were trees whose leaves were injured by 

 the frosts of 1910, of which we shall speak later, as the injured 

 leaves were often largely on lower branches. Finally, there 

 was no relationship in position between these trees and those 

 badly diseased. 



Concerning the effect of the so-called "blight" on the sub- 

 sequent growth of the trees, we may state that those that were 

 very badly injured have either died, or remained so stunted 

 in growth that their subsequent usefulness is quite doubtful. 

 Others that were rather severely injured have made some 

 growth, and their foliage condition, especially as to color, has 

 improved considerably, though the leaves often remain more or 

 less stunted and bunched. Those least injured have recovered 

 their normal leaf appearance, but are still somewhat backward 

 in their growth. Some few seem to have almost entirely recov- 

 ered from the effects, and are scarcely to be distinguished in 

 size and appearance from the surrounding trees that were not 

 injured. 



Concerning the cause of the sudden appearance of this 

 "blight" in 1907, we are now quite convinced that it was due 

 to the severe frosts that occurred on May 11 and 21 of that 

 year. We mentioned these as a possible cause in our previous 

 Report, but at that time we had no proof as to their connection, 

 as the "blight" was not called especially to our attention until 

 August. In 1910, however, we saw the same trouble produced 

 on certain pines by the late frosts of May and June of that 

 year. Soon after these frosts we found the leaves of scrub 



