The Take-all Disease of Cereals and Grasses 39 



of New York and its known occurrence in Oregon, Arkansas, Kansas, 

 Indiana, Tennessee, North Carolina, and California, indicates that it 

 has been present in this country for many years but has only recently 

 been recognized. Since the pathogene apparently was generally present 

 in the United States previous to the laying of the quarantine, this attempt 

 at exclusion cannot be expected to be of any importance in the control 

 of the disease. 



ERADICATION 



Investigators agree that when the take-all pathogene has once become 

 established in an area the most practical method of control is by eradica- 

 tion. The methods to be employed involve the killing of the ascospores 

 and the starving-out of the fungus. 



Cultivation has for its primary object the destruction of grass and 

 cereal harborers of the pathogene, and to accomplish this, the ground, as 

 Dawkins (1914) states, must be kept absolutely free of any grass on which 

 the fungus can thrive. This can best be done, according to Sutton (1911), 

 by cultivation soon after the wheat harvest and subsequent working of 

 the land after each rain. Other investigators, among them Gray (1914), 

 recommend one or two whole years of fallowing. The fallowing of the 

 ground for one or more years, as suggested for the Australian conditions, 

 cannot be followed everywhere. 



In New York the usual rotation practice makes it impossible to plow the 

 land after the wheat harvest. Rotation must be depended upon here to 

 starve out the fungus. 



There is a considerable difference of opinion as to the required length 

 of this rotation. If susceptible grasses, barley, and rye are not present 

 in the rotation, the length is given by Sutton (1911) as two years, by 

 McAlpine (1904) and Gray (1914) as three years, and by Richardson 

 (1911) and others as from four to six years. The importance of rotation 

 as a control measure may be inferred from the fact that during the 1921 

 and 1922 surveys in New York, it was observed that in nearly every 

 field in which more than five per cent of the plants were killed by take- 

 all, two or more successive crops of wheat had been planted. A rotation, 

 to be effective, should have wheat not oftener than every four or five years, 

 since the fungus can live in the soil for five months, and on the stubble 

 as spores for from nine to ten months; and if Agropyron repens or other wild 

 hosts are present, several years of cropping may be required to kill out 

 the grass and with it the fungus. 



The stubble of diseased wheat being the principal harborer of the take- 

 all fungus, some means of disinfection, such as burning the stubble, should 

 be applied to destroy this source of inoculum. Under Australian con- 

 ditions McAlpine (1904), Richardson (1911), and Brittlebank (1920) 

 advocate this means of disinfecting the field, but Sutton (1911) says that 

 a stubble burn is of doubtful value since it docs not destroy the under- 



