12 
BULLETIN 70. 
Some fields seem to be more favorable for the develop¬ 
ment of this fungus than others. A heavy poorly drained 
field seems to be of the favoring class. A thorough drain¬ 
age of the land would probably do much good. Potatoes 
grown on heavy soils with good bottom drainage usually 
suffer less severely from the disease than those grown on 
poorly drained soils. It is not definitely known how long 
this disease will remain in a field when it once becomes 
thoroughly established, but it is quite evident that land 
on which diseased potatoes have been grown usually har¬ 
bors the fungus a number of years, hence, it is important to 
follow a systematic rotation of crops, and it will probably 
be necessary to follow a five-year rotation in order to ob¬ 
tain good results. 
“Prunet * believes that the fungus remains in the soil 
three years, and recommends that diseased fields should 
not be cropped with lucern or clover for several years. 
Evidences indicate that root crops should be avoided. Cere¬ 
als which are probably not attacked by Rhizoctonia should 
be sown in the infected ground, and all weeds should be 
kept down. This is probably the only means by which the 
fungus can be destroyed.” 
Corrosive Sublimate Treatment. Corrosive sublimate or 
bichloride of mercury is sold in form of white crystals. It 
may be bought at any drug store for about fifteen cents an 
ounce. The cost of material for treating the seed for an 
acre will not exceed fifty cents. The solution is made by 
placing one ounce of this chemical in an earthen or 
wooden dish containing one gallon of hot water. As soon 
as it is all dissolved pour the contents of the dish into a 
wooden vessel containing seven gallons of water. Put the 
potatoes into this solution, and let them remain an hour 
and a half. The solution maybe used a number of times. 
The disinfection may be done at any time. Experiments 
indicate, however, that treating the tubers about a week 
before planting, and spreading them on the floor or ground 
where they will be fully exposed to the sunlight, greatly 
facilitates their growth after planting. Corrosive sublimate 
is a deadly poison to both man and animal when taken inter¬ 
nally , but the solution and treated potatoes may be handled 
freely without experiencing any ill results. 
FORMULA. 
Corrosive Sublimate. 1 ounce 
Water. 8 gallons. 
Soak Potatoes. 1£ hours. 
*(Prunet “Sur le Rhizoctonia de la Lucerne”. Compt. rend. 
Paris 1893. 
