PEANUT DISEASES 269 



borne than is 6". bataticola. Seed treatment should be effective against 

 most of the seed-borne inoculum. Since these organisms are universally 

 established in peanut soils, seed-borne inoculum may be a minor source 

 of infection. Seed treatment may be effective against a considerable por- 

 tion of the soil-borne inoculum, particularly in the case of S. bataticola, 

 which frequently infects seedlings through cotyledons. Close spacing of 

 seeds to insure replacements is also to be recommended. 



Collar Rot* 



Importance. In the southeastern United States peanuts are subject 

 to a stem and root rot which developed later than damping-off and seed- 

 ling dry-rots, and features otherwise distinct. The name "collar rot" is 

 proposed for this disease. Apparently such rots have been noted in the 

 southeastern United States for some time (97, 101, 111) and previous 

 reports have indicated that the problem is a complex one (101, 111). 



Collar rot was serious in several Georgia counties in 1946 and 1947. 

 In 1946 the entire stand was so depleted in a 10-acre field that replanting 

 was necessary. A similar situation was reported from Texas in 1941 

 (74). Serious depletions of experimental stands were observed in 1947 in 

 Georgia, and depletions of farmers' fields of runner peanuts were noted 

 in Alabama in 1947 and 1948^. A few references in the literature indi- 

 cate, indirectly, that an early root-rot disease is prevalent in other States 

 (74, 101, 111, 123) and the crown rot of peanuts described from Aus- 

 tralia (99, 100) bears many points of resemblance to collar rot. 



Description. Peanuts succumb to collar rot from emergence to early 

 flowering. The disease, however, seems most prevalent from 20 to 40 

 days after planting. When plants are attacked shortly after emergence, 

 hypocotyls are killed and there are black necrotic areas on cotyledons 

 and plumules. In early stages the main axis of plants are wilted with 

 necrotic areas in the region of the cotyledons, but side branches and root 

 systems are unaffected. Frequently a good mat of adventitious roots has 

 been formed just below the cotyledons. Next, the main axis dies and the 

 necrosis spreads downward on the taproot. A few plants recover even 

 after the main axis is dead and the taproot badly rotted. Undoubtedly this 

 recovery is due to good development of adventitious roots. The majority 

 of plants attacked, however, either die or remain stunted. The advanced 

 stage is characterized by dead taproot systems and side branches dying or 



* Based primarily on observations made in Georgia and on unpublished data of the Georgia Ex- 

 perintent Station. 



° Observations from unpublished data of the co-author, Coyt Wilson, Alabama Experiment 

 Station. 



