peanut diseases 263 



Peanut Diseases of Major Importance 

 IN THE United States 



DISEASES AFFECTING STAND ESTABLISHMENT 



Spotty stands of peanuts are common in the southeastern United 

 States (124) and other peanut-producing regions (43, 64). Since pro- 

 duction costs per ton are largely a function of area cultivated, these poor 

 stands are important considerations in the economics of peanut produc- 

 tion. 



Several things may account for spotty stands. The principal causes 

 appear to be: (A) Poor seed stocks (old seeds, improperly stored seeds, 

 seeds with fungus damage or mechanical injury, etc.). (B) Over-stretch- 

 ing of seed supply or improper spacing of seeds. (C) Inferior planting 

 equipment. (D) Unfavorable conditions after planting. (E) Depreda- 

 tions of field mice, birds, and other animals. (F) Seed rots and seedling 

 blights. 



Consideration of these items shows that disease is not the sole 

 factor causing poor stands. 



A number of distinct diseases affect peanuts early in the growing 

 season. When considered individually, many of these diseases do not ap- 

 pear to be of importance. Collectively, however, they often are serious. 

 Of these, the pre-emergence diseases probably have the most direct effect 

 on stand establishment in the southeastern United States (163). 



Pre-Emergence Diseases 



Importance. Soil rot of seeds is regarded as one of the three most im- 

 portant peanut diseases in Rhodesia (64). Its importance in the southern 

 United States must be obtained indirectly, primarily from the einphasis 

 placed on control programs in recent years. The most concrete evidence 

 may be obtained from reports of increased emergence of 15, 25 or up to 

 40 percent following such control programs (43, 45, 46, 103). 



Description. Planted seeds and very young plants are subject to two 

 types of diseases before emergence. The entire seed may be decayed, or 

 the developing embryo of young plant may be attacked by saprophytic 

 fungi, or damping-off fungi. Both of these types of pre-emergence dis- 

 eases have been reported on peanuts (43, 102, 105). 



Organisms. The organisms associated with pre-emergence diseases 

 have not been studied extensively. Soil-borne parasitic and saprophytic 

 fungi may decay seeds, particularly if germination is delayed or if the seed 



