UNIVERSITY 



OF 



AGRICULTURAL 

 EXPERIMENT STATION 



TIMELY HINTS FORFARMERS^ 



No. 118 



JULY 15, 1916 



CROWN GALL 



Crown gall is a widespread and dangerous disease, common to 

 deciduous fruit trees. It also attacks a number of small fruits, 

 some common field crop plants, and certain shade trees and orna- 

 mentals. It is known to be caused by a bacterial germ. This 

 organism, being minute, is easily spread from infected plants 

 to healthy ones through various agencies, including rodents, 

 insects (particularly borers), the careless use of pruning tools, 

 irrigation, and cultivation. 



Appearance of the disease. Knot-like galls or outgrowths appear 

 commonly on the crown of the plant, a little below the surface of the 

 ground. These are more or less smooth, but become uneven and 

 roughened when old, and may Attain the size of one's fist. At the 

 beginning of their growth they are milk-white, or translucent, but 

 within a few months become brownish in color and often have a 

 warty appearance. Smaller gall-like swellings from the size of a pea 

 to that of a walnut often develop on some of the smaller roots, or 

 rootlets, of the plant. These galls- appear on the roots and crowns 

 of plants in early summer, but usually stop growth in the fall. 

 This seems to be a matter of environment, however, for in warmer 

 climates they may develop in the winter. They increase rapidly 

 in size and cause a distinct malformation of the normal structure 

 of the infected parts of the roots. Occasionally, as in the instance of 

 the grape, pear, quince, rose bush, oleander, blackberries, and rasp- 

 berries the galls grow on the stems, trunks, or limbs and hence may 

 be seen readily. The trunks of certain varieties of quince trees are 

 at times much disfigured with crown gall, though the tree may 

 continue growth and bear fruit for some years. 



