AN INQUIRY INTO THE CAUSE AND NATURE OF 

 CROWN-GALX. 



By J. W. Toumey. 



INTRODUCTORY. 



In December, 1892, C. M. Wood wort h ' called attention to 

 fleshy outgrowths occurring in California on the^roots of decid- 

 uous fruit trees. As these outgrowths usually appear at the 

 crown, the name crown-gall was applied to this strikingly char- 

 acteristic disease. Several theories were advanced by Professor 

 Wood worth to account for the disease. It was briefly described, 

 and short comparisons were made between it and various root- 

 galls and knots produced by known causes. 



Professor Wickson, in an introductory note to the above 

 account, wrote as follows : 



"Almost everything imaginable has been cited as a probable 

 cause; conditions of drouth or of excessive moisture were among 

 the earliest causes assigned, and some prejudice against nursery, 

 stock grown by irrigation was created. An investigation by a 

 committee of the State Horticultural Society about 1880 showed 

 that the knotted roots were found quite as abundant in unirri- 

 gated laud as in irrigated, and otherwise the inquiry yielded no 

 definite results. For some time many nurserymen followed the 

 practice of removing the knots from the trees as dug from the 

 row, but this was abandoned when it was found that the knot 

 commonly reappeared after planting in the orchard. At pres- 

 ent no reputable nurseryman sells such trees ; they are burned 

 at the nursery. 



" Probably during the last 20 years hundreds of thousands 

 of such trees have spindled and died in the best soil and with 

 the best treatment. If the disease has stunted the growth of a 

 young tree, pluck it out and plant a new one. If knots are 

 found on larger trees which are making satisfactory growth in 

 spite of them, remedial measures should be tried. The final 



'Bull. Cal. Agr'l Exp. Sta., 99 (1892). 

 (7) 



