PEANUT DISEASES 287 



Two other types of interior damage can be confused with concealed 

 damage. In one type the interior of the cotyledons is shrunken, cracked 

 and discolored reddish-brown. Apparently this is a physiological trouble ; 

 no fungi have been isolated from these cotyledons and there is no ran- 

 cidity. It is rare (162) but has been found in several varieties and is 

 found more frequently in Virginia peanuts than is concealed damage. 

 The other type, a soft rot apparently beginning in the "germ," is rarely 

 noted (162). 



Organisms and pathogenicity. Mycelial mats between the cotyledons 

 of concealed damaged seeds suggest that a fungus is concerned, and the 

 disease has been reproduced by inoculations with fungi isolated from 

 seeds with concealed damage (48). 



The lists of fungi isolated from concealed damaged seed in Georgia 

 (48) and Alabama (162) are strikingly similar. Diplodia sp.^ made up 

 almost 90 percent of the isolations in both cases. Miscellaneous sapro- 

 phytes — Fusaria, Aspergilli, Penicilli, Sclerotium hataticola, etc. — ac- 

 counted for the bulk of the remainder. Parasitic forms such as Rhizoc- 

 tonia solani and Sclerotium rolfsii were rare. S. hataticola, however, was 

 isolated more frequently in Georgia (48) than in Alabama (162). 



Inoculation tests have shown that Diplodia sp. can produce concealed 

 damage (48). Therefore, it is regarded as the predominant organism in- 

 volved. Concealed damage was also reproduced by inoculation with 

 Sclerotium hataticola and perhaps one or two other fungi (48). Thus, 

 while most concealed damage is due to Diplodia sp., other fungi can and 

 sometimes do cause the damage. It has been suggested, however, that 

 Diplodia sp. is the pathogen and other fungi are secondary invaders (162). 



Concealed damage usually results from infection which takes place be- 

 fore peanuts are dug (162). The same fungi may be isolated from sound 

 seeds and from concealed damaged seeds (48). Concealed damage is 

 found when peanuts are bought on the market but the disease is rare in 

 freshly dug peanuts and then is found only in the early stage. It is ap- 

 parent, therefore, that concealed damage develops primarily during the 

 curing season. 



The causal fungus invades the intercotyledonary space through the 

 shell and the placenta (48). Thereafter growth of the fungus is condi- 

 tioned by moisture content of the seed. The damage develops most rapidly 

 in green peanuts with moisture contents IS to 35 percent (162). Above 



» The taxonomy of the form genus Diplodia is extremely confused. The fungus isolated from 

 concealed damaged seeds could he put in any of feveral species including three species originally 

 described from peanuts. The present report prefers to regard it as "Diplodia sp." until it has been 

 studied further. 



