40 Robert S. Kirby 



ground parts on which perithccia arc produced. Under New York con- 

 ditions the burning of stubble would kill the clover seeding which is 

 planted with wheat, and would thus be of doubtful value. Straw, which 

 would be likely to contain culms broken or cut off low enough to make them 

 carriers of the organism, should be disposed of in such a way that none 

 of the stubble or straw is returned to the land in manure or in other ways 

 for at least three years preceding the planting of wheat. Observations in 

 1921 showed that wheat straw from diseased fields, when applied in 

 manure during the fall and winter of 1920-21, acted as a direct carrier 

 of the fungus. 



PROTECTION 



The first measure by which protection is to be obtained is by modifying 

 moisture relations. Humidity of the soil has been reported as being 

 favorable to the disease (Robinson, 1907, and Mangin, 1914), and the 

 present investigations seem to confirm this theory. Low, wet soil should 

 therefore be drained before the wheat is planted. 



The second measure of portection is by modification of temperature 

 relations. From the evidence presented under Ecology, it appears that 

 high temperatures in the fall increase the amount of seedling infection. 

 The planting of winter wheat as late as possible will reduce the amount 

 of infection and the resulting amount of diseased and badly dwarfed plants 

 at harvest time. 



The third measure of protection is by modifying the chemical reaction 

 of the soil. Brittlebank (1920) found that an alkaline soil produced more 

 take-all than one which was non-alkaline. The present investigations 

 show that the addition of lime increases, and the addition of acid or 

 acid-forming substances decreases, the percentage of badly diseased 

 plants. A study of the germination of ascospores and the rate of growth 

 of the organism at different degrees of acidity indicated that acid added 

 to the soil acts as a barrier between the pathogene and the susceptible 

 roots of the host plants, in some way, probably by inhibiting the germina- 

 tion of the ascospores and the growth of the fungus. It was observed also 

 that the yield of uninfected plants was reduced as the acidity increased 

 below pH 7. The advisability of using acid on the soil to control take- 

 all would therefore be dependent on such factors as the severity of the 

 disease in any one locality and the degree of tolerance to acid conditions 

 of the other crops in the rotation. 



The results seem to indicate that where wheat, barley, rye, and potatoes 

 are the only crops in the rotation, and where the disease is severe, the 

 application of a moderate amount of an acid-forming substance would 

 be a profitable control measure. In New York certain crops such as 

 clover, which is intolerant to acid conditions, are often grown in the 

 rotation. It therefore seems unlikely that the addition of acid would 



