PEACH DISEASES 287 



The prevailing opinion of the modern pathologists is that 

 the disease is caused by a parasite which as yet has not been 

 seen. It was long ago established that the disease is communi- 

 cable, that is, the causal factor may be transferred from a 

 diseased tree to a healthy one, and after a time the latter tree 

 will show symptoms of yellows which in due time run their 

 course'. Buds from diseased trees convey the causal factor of 

 yellows to the stock on which they are inserted. The inocu- 

 lum, whatever its nature, is apparently carried in a few diseased 

 cells which, if induced to unite with normal cells of the stock, 

 will cause the stock to become diseased. Diseased seeds also 

 carry the inoculum; and there are probably other ways in 

 which it is carried. 



Control. 



The knowledge of remedial measures is about as meager 

 as that of the causal relations. "Cures" are worthless and 

 impossible. It has been shown that while fertilizers make the 

 trees temporarily greener and apparently more vigorous, yet 

 in the end they are of little or no value in the control of yellows. 

 Trees have been treated with such materials as lime, wood 

 ashes, kainit, muriate of potash, dissolved bone-black, bone-ash, 

 nitrate of potash, nitrate of soda, sulfate of ammonia, tobacco 

 dust, dried blood and stable-manure. Treated trees are just 

 as likely to be attacked as those left untreated. 



The prompt removal and destruction of affected trees has 

 been recommended since 1828. The advice is still reliable. 

 It has been practiced effectively in the State of Michigan in 

 years past. The eradication of diseased trees must be an 

 annual operation until no traces of yellows remain. Where 

 no such efforts have been made to exterminate the disease, 

 it has prevailed to such an extent that orchards have been 

 destroyed and the culture of peaches abandoned. In order to 

 accomplish general and effective eradication, laws have been 

 enacted in many states. The first was enacted by the legis- 



