PEANUT DISEASES 303 



Phyllosticta Leafspot 



In the southeastern United States primary and other seedling leaves 

 of peanuts are always infected with a leaf-spot organism. The spots differ 

 from typical peanut leafspot (Ccrcospora spp.) in being smaller, more 

 irregular, without definite halos, and in being found only on juvenile 

 leaves. Moist chamber culture of leaves shows that a Phyllosticta sp. is as- 

 sociated. This organism apparently cannot infest older leaves. It is also 

 apparent that the peanut plant is not noticeably damaged by these leaf- 

 spots on younger leaves. There is also a report from Burma of the occur- 

 rence of a Phyllosticta on peanuts (117). 



FusARiuM Wilt or Root Rot 



Many peanut-disease surveys made in southern United States have 

 listed Fusariiim wilt on peanuts. In Texas a seedling blight, apparently 

 due to a Fusariiim sp., was regarded as one of several factors necessitat- 

 ing replanting of several fields in 1941 (75). In Georgia in 1932 (92) it 

 was reported that an early or seedling wilt caused by F. martii var 

 Phaseoli Burk. depleted stands from 10 to 38 percent in some counties. 

 Fusaria can be isolated from peanut seeds readily and isolations from 

 "diseased peanut tissue" in North Carolina were approximately 50 per- 

 cent Fusaria ( 101 ) . 



In 1932 a Fusarinin sp. was shown, by inoculation, to be the cause of a 

 "destructive" wilt of peanut in Kenya, Africa (89), but since then con- 

 tinuous selection has maintained sufficiently high resistance to keep up 

 production (65). 



The following description of a Fusariiim wilt of peanuts is based on 

 that given by Miller and Harvey (92) from Georgia: Maximum infection 

 occurs at blooming. Entire plant is usually killed, but sometimes only the 

 shoots. Lesions on roots at first are small, elongate, light-centered with 

 darker edges. Roots eventually are girdled by enlargement of lesions. Rot 

 progresses through the roots with hyphae evident in the disintegrating 

 tissue. There is no plugging of xylem vessels. In advanced stages the 

 taproot is rotted just below soil surface. 



The Fusariiim "wilt" of peanuts, as described, is not a typical wilt. 

 The plugging or disintegration of conducting cells usually found in wilts 

 has ijot been reported from peanuts. Rather the peanut disease, as noted, 

 was a typical root rot. 



It is difficult to establish the pathogenicity of a Fusarium sp. The 

 senior author has made numerous unsuccessful attempts to prove patho- 



