PEANUT DISEASES 283 



If fungi infect the peg it may decay the pod in the soil, or it is weak- 

 ened so that the pod is puUed-off in the soil or otherwise lost in harvest- 

 ing. Attacks upon the nut result in discoloration or decay of the shells and 

 eventually in discoloration and partial or complete decay of the seeds. 

 This fungous invasion of the maturing peanut fruit may be facilitated by 

 insect or nematode action (113, 161) but it is not dependent upon this. 



Preharvest sprouting of seeds is frequent in Spanish peanuts and 

 certain peanut varieties other than the common runner that do not re- 

 quire an after-ripening period before germination. Large numbers of 

 sprouted seeds are found on Spanish peanut vines when the pegs show 

 evidence of considerable fungous infection. This indicates that fungi may 

 be responsible for considerable preharvest sprouting of seeds. Probably 

 infection of the peg stops the movement of water and food materials re- 

 sulting in premature ripening and abnormally early germination. 



Infection of the peg, however, is the only one of the causes of breaking 

 of pegs at harvest ( 139) . At maturity all vegetative parts of the plant are 

 brittle. Premature leaf shedding from disease or insect attacks also has- 

 tens vegetative maturity and the pegs become brittle abnormally early. 



Organisms. Peg breaking or seed damage may result from action of 

 a number of common soil fungi. Fungi isolated from soil-rotted peanuts 

 (13, 96, 109, 113, 118) and from peanut seed stocks (41, 44) show that 

 a variety of saprophytic and parasitic fungi is associated with pod rots. 

 Nematodes have also been reported as a cause of damage to peanut pods 

 (113). 



Somewhat detailed isolations (161) showed about one-half of the 

 rotted fruits were infected with miscellaneous molds {Penicillia, Asper- 

 gilli, Rhizopus spp., etc.). The remainder were infected with Sclerotium 

 rolfsii, S. bataticola, Diplodia sp., Rhizoctonia spp., or Fusaria. S. rolfsii 

 was reported several years ago ( 168) as a cause of peanut fruit rots and in 

 1931 (91, 98) and 1943 (150) it was reported as the predominant organ- 

 ism apparently associated with soil rots of peanuts. The variety of fungi 

 isolated from field-rotted nuts ( 161 ) suggests that 5". rolfsii is usually not 

 the most important organism, but rather is only one of several important 

 organisms. 



Early defoliation of plants also causes peg breaking. Thus any dis- 

 ease or insect injury resulting in leaf shedding will increase losses due to 

 peg rot. 



Some cases of peg breaking can only be blamed on over-maturity of 

 the pegs at harvest. This is a result of miscalculations and cannot be 

 called a disease. 



Control. Since maturation diseases are affected by several factors. 



