SOME STEM TUMOKS OK KNOTS ON APPLE AND QUINCE TREES. 15 



SUGGESTIONS TO NURSERYMEN, NURSERY INSPECTORS, AND 



ORCHARDISTS. 



Nurserymen are advised to be careful in the selection of scions and 

 stocks for jDropagation and to see that they are always taken from 

 healthy trees. The experiments of the writer in the case of the apple 

 indicate that all forms of hairy-root on scions increase where the 

 scions are taken from diseased trees. 



The following suggestions based upon experiments and observa- 

 tions are made to nursery inspectors: Apple or quince trees badly 

 diseased with any of the forms of hairy-root, whether aerial, woolly- 

 knot, or simple, should be discarded as unfit for planting. Figures 

 1, 2, 3, 4, 9, and 10 represent severe types of aerial, woolly-knot, and 

 simple forms of hairy-root. The last two forms occur on the roots of 

 trees in the nursery, while the first is found as a rule only on orchard 

 trees, probably as a later development of the more intense forms of 

 the disease on the roots. 



If all trees affected with traces or milder forms of the disease as it 

 occurs on the roots were discarded, it would mean the rejection of 

 nearly all of the trees grown in some localities. Such trees when they 

 have a vigorous root system, notwithstanding traces or mild forms of 

 the disease, apparently grow as well as healthy trees with smooth 

 roots, or in some cases may grow better for the first few years, so far 

 as has been ascertained by experiments and observations. Until it can 

 be shown that the presence of the milder forms of the disease on the 

 roots of nursery trees will lead to its further spread in the orchard, or 

 that such trees are unprofitable for planting, it does not seem justifia- 

 ble to condemn them. On the other hand, the writer is not ready to 

 assert that they are equally as good for planting as trees with smooth 

 roots. 



There is a difference of opinion as to what constitutes a healthy 

 root system ; some would limit the application of the term " healthy " 

 to trees entirely free from fibrous root formation on the main roots. 

 The writer has observed that trees with a very fibrous root system 

 are often the product of certain kinds of soil and are apparently as 

 healthy as trees more nearly free from such roots. Such trees are 

 equally as good for planting as those with smooth roots and might 

 easily be mistaken for diseased trees slightly affected with traces of 

 hairy-root. Until it can be shown that fibrous roots are inferior to 

 smooth roots and that the milder forms of hairy-root seriously affect 

 orchard trees, the writer is not ready to recommend the destruction 

 of such trees in the nursery, since this course would probably involve 

 an unnecessary loss of many thousands of dollars to the nurserymen 

 and a consequent increase in the price of trees to the orchardists. 



[Cir. 3] 



