Papers on biology and agriculture 203 



for in a year or two all roots left at the first digging will 

 have sprouted and can be removed. With bushes grow- 

 ling wild in pastures and woodlots and along fences at a 

 distance from the house, the situation is different, and 

 other means of killing the bush are desirable. 



In the past two years experiments have been carried 

 on at Gurnee in Lake County in an effort to find some 

 suitable chemical that would kill barberry bushes. A 

 large area of escaped barberry was found at Gurnee in 

 June, 1921, and the chemical experiments were begun in 

 the autumn of the same year. Noel F. Thompson, who is 

 now in charge of the experiments, has found that rock 

 salt and a commercial compound containing sodium 

 arsenite are the most effective compounds for killing the 

 bushes. 



Dr. W. W. Robbins conducted a series of experiments 

 to determine a satisfactory method for killing barberry 

 seedlings. He found that a number of chemicals are ap- 

 parently equally toxic to barberry seedlings. Sodium 

 arsenite was the most economical and effective compound 

 used. A spring application was more effective than a 

 fall application. Apparently the seedlings gain in re- 

 serve strength as the season advances. This fact sug- 

 gests the advisability of spraying the young plants as 

 soon as possible after the germination of the barberry 

 seeds in the spring and summer. 



Because of the danger to livestock resulting from the 

 use of sodium arsenite, it has become necessary to dis- 

 continue using this chemical and to rely entirely upon 

 salt. 



There are many localities in Illinois where the soil is of 

 such a character that effective digging of the bushes is 

 impossible. An example of such a condition was encoun- 

 tered in the Galena district. The soil of the entire region 

 is extremely rocky and where bushes were removed in 

 July, sprouts appeared in September, thus demonstrat- 

 ing the absolute necessity of adopting the more efficient 

 method of using chemicals in order to eradicate perma- 

 nently every common barberry bush in the State (Fig. 3). 



Even when the character of the soil would not inter- 

 fere with eradication by digging, sprouts have been found 



