EXTERMINATION OF WEEDS 99 



Formaldehyde. Formaldehyde, although an excellent 

 germicide, has been recommended for the extermination 

 of weeds, but it is less effective than carbolic acid. In 

 1907 an experiment was conducted with formaldehyde, 

 using 4 per cent formalin at the rate of 2 3-4 barrels per 

 acre. The plants experimented with were quack grass, 

 pigweed, foxtail, and lamb's quarter. While the plants 

 were injured somewhat by the treatment, the annuals 

 more than the perennials, soon after the treatment they 

 became as vigorous as ever. 



Corrosive Sublimate. This powerful disinfectant has 

 been used for the destruction of potato scab and to some 

 extent for the destruction of the spores of fungi. Professor 

 Bolley has found it successful in the treatment of 

 potato scab when used in the following proportions : 

 2^2 oz. corrosive sublimate to 15 gallons of water. It is 

 an excellent germicide and antiseptic, but its use as an 

 herbicide cannot be recommended because of the great 

 danger involved from the poisonous character of the 

 chemical. 



Sodium Arsenite. Bolley finds this a valuable spray 

 when used at the rate of i^ Ibs. to 52 gallons of water. 

 Professor Bolley recommends the use of sodium arsenite only 

 where weeds grow in clumps, like the Canada thistle, bur- 

 dock, and other weeds with persistent underground 

 stems. In such cases the solution can be applied by 

 hand, or if applied with a machine it can be done without 

 regard to the injury of the crop. He considers this the 

 best weed killer on the market. The product on the 

 market frequently contains sodium arsenate, which is 

 very destructive to grains. The arsenical solutions are 

 poisonous and must be used with caution. 



Sodium Arsenate. Sodium arsenate has proven very 

 successful in the extermination of some weeds. Jones 

 and Orton, Edson and Jones, reported it as satisfactory 

 when used in the proportion of one pound of arsenate to 



