42 MAINE AGRICULTURAL EXPERIMENT STATION. I914. 



time the plants had developed eight leaves,) the field was en- 

 tirely freed from this pant despite the fact that the oats were 

 so tall that they partialy covered the wild turnip plants, and 

 that the plants were far larger than they should be for treat- 

 ment. 



It is rarely that a field is badly infested with more than one 

 of these varieties. If it is the wild mustard or the wild turnip 

 it can be more readily controlled than the wild radish. How- 

 ever, all three of the plants can be controlled by spraying with 

 iron sulphate at the proper time and under proper conditions. 



IDEAL CONDITIONS. 



While it is not always possible by any means to spray at 

 exactly the right time and under exactly the right conditions 

 the following are the points to be aimed at : 



It is of the utmost importance to spray the plants while they 

 are small and before the buds form. They should not be in 

 more than the third or fourth leaf, for if they are much larger 

 than that there is danger that the plants will not be killed but 

 only injured by the spray. The plants should be so small 

 that they can be completely covered b}^ an ordinary drinking 

 tumbler. 



There should be used common iron sulphate and water. 

 Dissolve so as to make a 17 to 20 per cent solution. The solu- 

 tion is made by suspending 100 pounds of the iron sulphate in 

 the top of a barrel containing 50 gallons of water. If allowed 

 to stand over night the major portion of the iron sulphate will 

 be dissolved and only a small amount of labor is needed in 

 the morning to complete the solution. This solution will have 

 a strength of about 22 per cent, and for use should be reduced 

 by the addition of about 20 gallons of water to make the solu- 

 tion contain about 17 per cent of iron sulphate. 



The solution must be applied as a very fine mist. Sprinkling 

 will not suffice. An ordinary potato sprayer which can develop 

 power sufficient to maintain a pressure of 60 to 70 pounds to the 

 square inch, by the use of fine nozzles, will make the desired 

 mist. 



The plants should be sprayed after the dew has dried off in 

 a still air and on a bright sunny day. It is not usually possible 



