FORTY-FIRST ANNUAL REPORT. 53 



The only suggestion respecting the origin of the yellows we have seen 

 is that given in the Year Book of the United States Department of Agri- 

 culture for the year 1898. by William Saunders, then horticulturist of 

 the department. He says : 



"The action of sudden freezing of immature and imperfectly ripened 

 wood in the fall or early winter is a fruitful source of disease. That 

 apparently incurable malady in plants known as 'yellows,' in the opinion 

 of the writer, based on forty years' experience, is the result of sap con- 

 tamination of these frozen points, the prompt removal of which will, 

 he is convinced, prevent the spread of the disease, and thus save the 

 plants from speedy and ultimate destruction," 



While this may account for its origin it is evident that frozen wood 

 is not the only means by which the disease spreads. While nothing is 

 known regarding the nature of these diseases and the method by which 

 they extend, it is reasonable to suppose that when they appear in a 

 region remote from where they have been found before, they are brought 

 in u]X)n infected nursery stock. I am convinced that the danger from 

 this source is small, however. I never have seen either of these diseases 

 in trees that have been planted in the orchard less than three years, 

 though some have told me they have seen the yellows on younger trees 

 than this. Careful experiments by Dr. p]rwin F. Smith of the United 

 States Department of Agriculture and others have shown that pits from 

 premature jieaches will not grow, and that buds taken from the appar- 

 ently healthy part of a tree showing the yellows on one side either make 

 no growth at all or show the disease within a very short time. It seems 

 reasonable to conclude, therefore, that nursery trees that may be in- 

 fected in either of these ways will show the disease before they are 

 ready to put upon the market. But there is a probability that trees 

 growing in the nurser\- may be infected from diseased trees growing 

 in the vicinity. There will always be danger from this source where 

 trees are obtained in sections where yellows prevails. With resi)ect to 

 the spread of the little peach by either of these means nothing has been 

 shown by experiment so far as T am aware, we can only conclude from 

 analogy that similar conditions exist. 



With respect to the spread of these diseases it seems that their progress 

 from place to place is comparatively slow. An orchard three years under 

 my care, adjoining a township in which no yellows commissionei*s had 

 been appointed, twenty years ago went out entirely with the yellows 

 and the trees on an adjacent farm suffered badly, while an orchard two 

 and one-half miles away at the same time did not have one per cent of 

 the trees affected in any year. It was observable, too, that when the 

 malady was most prevalent occasionally a grower neglected to remove 

 his diseased trees promptly, didn't think it was "catchin'," some being 

 so negligent in this respect that arrests were made under the yellows 

 law. These men invariably lost their orchards in a short time, and their 

 immediate neighbors suffered severely, but in orchards a mile or two 

 away there was no appreciable increase in the number of diseased trees. 



Where either of these diseases exists to any considerable extent it is 

 doubtless unwise to ]>lant new orchards in the immediate vicinity for 

 a few years, until the number of affected trees is reduced to a minimum, 

 but experience abundantly shows that in IMichigan vacancies caused by 

 the removal of diseased trees may safely be replanted the following 



