8 Department Circular 376, U. S. Dept. of Agriculture 
and helpful in the control. Melhus and Maney ® also report the use 
of Bordeaux mixture as a dip for apple grafts. 
There is a possibility that the grafting knives or other tools and. 
the benches and tables may become infected. It is not probable that: 
all obscure cases will be eliminated in the inspection, and dormant 
infection would, of course, escape notice. Furthermore, the knives: 
may cut through bacterial infection beneath the thin outer bark 
which was not reached by the disinfectant. Although there is no 
definite proof that stock can be contaminated with crown gall by 
means of grafting knives, there is proof that the pear-blight or- 
ganism can be carried on grafting or pruning knives. In view of 
the fact that it is rather easy occasionally to disinfect the tools 
and grafting benches, it is thought good practice to utilize this 
method of control, even though its value is not fully proved. 
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 years: 
(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 consisting of 1 part of hydroxymercurichlorophenol * to 400 parts of 
water (approximately at the rate of 1 ounce to 8 gallons). In this as well 
as in subsequent dips do not rinse with water, and keep the solution in either’ 
a wooden or a nonmetallic container. 
(3) Dip the grafts, 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 grafts 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. 
shee Seg nD et 
3 Melhus, I. E., and Maney, T. J. A study of the control of crown-gall on apple grafts 
in the nursery. Iowa Agr. Exp. Sta. Research Bul. 69, pp. 159-172. 1921. 
4 Obtainable on the market in powdered form under the trade name “ Semesan.”’: 
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