Oct. i, 1920 Fusarium-B light (Scab) of Wheat and Other Cereals 7 



aerial roots, a development quite common in oats, and before long the 

 effects of the attack may largely disappear. 



ON STEMS OF GROWN PLANTS 



Occasionally full-grown plants are killed by Qibberella saubinetii or 

 by one of several Fusarium species just before or shortly after the 

 time of blossoming. The fungus attacks the roots and the stem close 

 to the ground, the first node usually being involved in the infected area. 

 The part of the stem in contact with the ground and the roots below are 

 rotted and are commonly pink or yellowish brown in color. This rotting 

 of the base interferes with the water and food supply of the plant, and 

 wilting of the entire plant is the result. Such plants become bent or 

 broken over soon after they wilt and hence are easily recognizable in 

 well-kept fields. When such plants are pulled up they break at the base, 

 the roots always remaining in the soil (PI. 2, A). It must be remembered, 

 however, that wilting of the whole plant in very much the same way is 

 caused by other fungi as well, for example by Colletotrichum sp., although 

 in attacks by this fungus the base of the dead plant is a much darker 

 brown or black in color. 



This infection at the base of the plant may be due to any one of several 

 causes. It may be only a continuation of the attack upon the young 

 seedling or it may be the result of a new infection. Either the decline 

 in vigor or unfavorable weather conditions may be responsible for the 

 appearance of the disease at this time. 



The succulent embryonic tissue just above the nodes of the various 

 cereals is especially susceptible to attack by Qibberella saubinetii. Here 

 the infection is usually restricted to the node or the area immediately 

 next to the node, seldom, if ever, extending more than 2% cm. in each 

 direction. In such cases the portion above the infected node usually 

 wilts and soon dies. Conidia may be formed under certain conditions 

 on the node itself and on the infected part of the sheath coming out from 

 it. This condition was first observed by McAlpine (4, p. 305) in 1 896. 



BLIGHTING OF HEADS 



Wheat. — The symptoms and effects of headblighting of different 

 varieties of wheat are, in general, the same. The blighted head usually 

 takes on the normal color characteristic of the ripe head of that variety 

 or a slightly lighter color. 



Blighting of the wheat heads can be detected with absolute certainty 

 at a very early stage, three to four days after infection has taken place, 

 provided that weather conditions have been so favorable as to enable 

 the parasite to establish itself on the host and to begin its work of 

 destruction. 



The symptoms of blight infection as they appear on Marquis or some 

 other of the beardless varieties are as follows : The very first sign of blight 



