8 



CIRCULAR 3 7 6, U. S. DEPARTMENT OF AGRICULTURE 



The following treatment of apple grafts for the control of crown 

 gall is recommended as a result of a large number of experiments 

 over a number of jears : 



(1) Select seedlings free from hairy-root and crown-gall infection. 



(2) After washing, dip for 

 10 minutes uncut seedlings 

 and scions in a solution con- 

 sisting of 1 part of hydroxy- 

 mercurichlorophenof^ to 400 

 parts of water (approxi- 

 mately at the rate of 1 ounce 

 to 3 gallons). In this as 

 well as in subsequent dips 

 do not rinse with water, and 

 keep the solution in either a 

 Avooden or a nonmetallic 

 container. The uncut seed- 

 lings and scions should be 

 allowed to become surface 

 dried before cutting for the 

 grafting operation. 



(3) Dip the gi-afts, which 

 should be well fitted and 

 carefully wrapped, in this 

 same freshly made solution 

 for about 5 seconds.® 



(4) Store grafts under 

 cool conditions and dip 

 them for about 5 seconds 



in a freshly made solution of the mercury compound immediately 

 before planting.® 



(5) Keep the bench on which the grafting is done, as well as all 

 grafting tools, disinfected by frequent washings with a germicide. 



Fig. 8. — Trees from untreated Ben Davis grafts 

 grown as checks for the lot illustrated in Fig 

 ure 7. Reading from left to light 

 (48), doubtful (4). clean (61) 



Galled trees 



5 Obtainable on the market in powdered form under the trade name " Semesan.'" 

 " Later experiments have shown excellent control with the first dipping alone and very 

 little additional benefit from the second and third dippings. Since there has been found to 

 be some danger of injary, under unfavorable conditions of storing and growing the grafts, 

 by the second and third dippings here suggested, it is possible to eliminate these addi- 

 tional dippings without appreciable loss of control. 



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