312 THE PEANUT— THE UNPREDICTABLE LEGUME 



Disease-Like Results of Insects. Certain effects of insects on plants 

 are sometimes difficult to distinguish from pathogenic diseases. An ex- 

 ample is "peanut pouts" originally regarded as a disease of unknown 

 cause. The swollen, distorted areas on leaves and young stems were 

 shown by Metcalf (90) to be the result of toxins from mass-attacking 

 leafhoppers. It was later pointed out that thrips injury is also sometimes 

 referred to as peanut pouts (128). 



RARE OR ACCIDENTAL DISEASES 



Any crop is sometimes found attacked by fungi under "unusual" cir- 

 cumstances. It is rare that such unusual diseases assume any importance, 

 and they have never been regarded as important on peanuts. Only a few 

 diseases of this type have attracted sufficient attention to be reported. 



1. Seedling rots caused by mold-type fungi. Seedlings of peanuts are 

 sometimes killed by overgrowth of mold fungi (72). Almost always 

 extenuating circumstances are obvious : The seedling has been suppressed 

 or wounded by growing under a hard soil crust ; there has been exces- 

 sively heavy rainfall coupled with excessively low temperatures ; or some 

 other equally apparent circumstance. The fungus overgrowth is usually a 

 Rhizopus sp., Penicillium sp., or Aspergillus sp. 



2. Fungus leaf spots following insect injury. Typical fungus-type leaf 

 spotting sometimes develops following insect injury. For example, an 

 Alternaria sp. leafspot has been reported from Virginia (11) associated 

 with leaf-hopper damage. Undoubtedly these unusual leafspots are very 

 unimportant in the total picture of peanut diseases. 



3. Diaporthe blight. A situation has been reported from Virginia (12) 

 in which Diaporthe phaseolorum var. sojae (Lehm.) Wehm. was sus- 

 pected as the initial cause of the death of peanuts. In a later study (84) 

 neither the species D. phaseolorum (C. and E.) Sacc. nor the variety 

 could be shown by inoculation to be pathogenic to peanuts. 



4. Anthracnose of peanuts. There are only two reports on the occur- 

 rence of anthracnose fungi on peanuts. A Colletotrichum sp. was ob- 

 served on peanut leaves in Uganda, Africa, in 1926 (130) and Colleto- 

 trichum sp. was the most abundant fungus in a few dark-colored stem 

 lesions on peanuts in Oklahoma in 1944 (78). 



MISCELLANEOUS FUNGI 



A large number of fungi have been reported from peanuts only once 

 and the reports are now buried in obscurity. Host indexes list species of 

 fungi on peanuts for which it is impossible or almost impossible to find the 



