FUNGI AND PLANT DISEASE 425 



crops, but the blackened, fungus infected heads cause poisoning 

 if they are present in sufficient quantity. On wheat, this disease is 

 rarely destructive, but under certain conditions may become so. 

 When present in only small amounts, ergot may cause rejection of 

 wheats for manufacture into macaroni and spaghetti since the 

 infected heads would cause black streaks in the resulting product 

 and make it unfit for sale. The ergot fungus infects the ovary of 

 the cereal flower, either destroying it entirely, or causing a mal- 

 formation of the resultant grain. The fungus further develops to 

 form a mycelium which completely fills the blighted grain, 

 finally producing a black, very heavy-walled resting mass of 

 mycelium known as a sclerotium. These sclerotia resemble ma- 

 ture grains in shape, but are often more elongated, and their 

 presence is easily detected. The fungus winters in the sclerotium 

 stage, sometimes with the seed, but often in the field. In the 

 spring, the heavy walls of the sclerotium soften, and the mycelium 

 develops into several spore-bearing structures which produce 

 numerous asci. These produce the spores which cause infection 

 in the new grain crop. Warm, wet weather favors heavy infection 

 of a field, since it causes the flowers to remain open longer, and 

 likewise is favorable to the development of ascospores. Control 

 of ergot is eff'ected by the use of disease free seed, by the rotation 

 of crops — that is, if infection has been evident in a preceding 

 cereal crop, some other crop should be grown in the particular 

 field until the fungus has had an opportunity to die out — and 

 finally by the removal of susceptible wild grasses from fence rows. 

 Near-by pastures of susceptible grasses should be either closely 

 grazed or mowed before flowering time to prevent infection and 

 subsequent spread of the disease to grain fields. 



Brown rot of stone fruits occurs generally throughout the 

 United States where such fruits as apricots, peaches, cherries, 

 plums, and apples are grown, but is especially destructive to 

 certain kinds of plums grown in the mid-west, and under favor- 

 able conditions is one of the worst diseases of the peach crop. 

 The fungus may attack leaves, twigs, flowers, or fruit, causing at 

 first a symptom that may be mistaken for frost. Although brown 

 rot does cause damage to foliage and twigs by killing them, it is 

 most destructive to the fruit, gaining entrance by natural open- 



