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_ i g P A R Y 

 UNITED STATES , || 



DEPARTMENT of AGRlCtLWRE / 



DEPAETMENT CIRCULAB 376 



Washington, D. C. 



?^«cr. famuLd Jauual j , IJiU " 

 Revised November, 1928 



A. METHOD FOR THE CONTROL OF GROWN 

 GALL L\ THE APPLE NURSERY 



M. B. WAITE 



Principal Pathologist in Charge 

 and 



E, A. SIEGLER 



Associate Pathologist, Office of Fruit Diseases, Bureau of Plant Industry 



Introduction 



Experiments and results. 



COXTENTS 



Page 

 1 



Page 



Discussion 



Recommendations for control. 



INTRODUCTION 



The problem of crown gall in the root-grafted apple nursery is a 

 very serious one. The nurseryman who has to discard only 5 to 10 

 per cent of his trees on careful inspection at digging time is usually 

 considered fortunate. Losses of 2d to 5U per cent are not uncommon, 

 and certain lots of trees in extreme cases have even shown a loss 

 of 95 per cent. These serious losses to nurserymen and also the 

 general interest of orchardists in obtaining disease-free stock for 

 planting have made the writers feel the importance of this phase 

 of the crown-gall j^roblem. Present-day nursery stock, especially 

 when grown by the root-grafting method, appears to contain a 

 higher percentage of infection than formerly, and there also appears 

 to be more trouble in recently planted apple orchards than in those 

 planted a generation ago. AVhether this supposition is true or not 

 may be open to question. It may be that nursery and orchard trees 

 are examined more critically as increased attention is given to 

 orchard diseases. 



Before the bacterial cause of this disease was known George G. 

 Hedgcock, in his extensive studies of crown gall, tried many experi- 

 ments in the propagation of root-grafted apple trees and made many 

 observations which resulted in progress toward the control of this 

 disease. The discovery of the bacterial nature of this previotisly 

 obscure disease by Erwin F. Smith and his associates in 1907 marked 



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