278 THE PEANUT— THE UNPREDICTABLE LEGUME 



but feel that 6". rolfsii may be a secondary invader and, therefore, are not 

 wilUng to attribute the losses to this organism. 



Sclerotium rolfsii seldom kills the entire plant of runner peanuts since 

 portions away from the point of attack are usually supported by the ad- 

 ventitious root system. Therefore, the disease is not as spectacular on 

 runner peanuts as on bunch peanuts. There are three general views as 

 to the importance of S. rolfsii on runner peanuts : (A) Runner peanuts 

 are sometimes regarded as somewhat resistant to S. rolfsii; (B) i'. rolfsii 

 is sometimes called an important peg-rotting organism, but an unimpor- 

 tant blight-producing organism on runner peanuts; (C) finally S. rolfsii 

 is frequently regarded as an important blight-producer on runner peanuts. 



Thus, there is a divergence of opinion as to the importance of this 

 disease in the United States. This undoubtedly results largely from a com- 

 bination of three factors: (A) The newness of peanuts as a commercial 

 crop in some areas ; (B) a tendency to question the parasitism of Sclero- 

 tium rolfsii (12, 101) ; (C) the somewhat different end response to at- 

 tacks of S. rolfsii exhibited by bunch peanuts as compared with runner 

 peanuts. 



Sclerotium blight is well known in other peanut-producing regions. 

 In South Africa, where it is known as "foot rot," it has been reported as 

 jeopardizing the future of peanut growing (22). In the Philippines, pro- 

 grams have been initiated, attempting to discover varietal resistance 

 (115). Losses reported for this disease in Peru vary from light to heavy 

 (40). A disease has been reported from Rumania (200) and Bulgaria 

 (34) that appears to be Sclerotium blight. It is a matter of conjecture 

 whether or not the disease is important in such areas as Australia, al- 

 though its importance in Ceylon has been questioned (17). 



Description. The two most distinctive characteristics of Sclerotium 

 blight are death of above-ground portions of plants and a mat of white 

 fungus hyphae and tannish-red sclerotia around stems at the soil surface. 

 The entire plant or only one or two branches may be killed (22, 92, 150) . 

 When only branches are attacked on bunch peanuts the unattacked por- 

 tion may remain healthy and vigorous, or it may be stunted and yellow- 

 ish and have few or no nuts at maturity. The unattacked portions of run- 

 ner peanut plants usually remain vigorous, although nut production may 

 be poor. 



The center of infection is at the soil surface, and death of above- 

 ground portions of plants is due to severance of the water-conducting 

 tissue of the roots and stems. The leaves usually wilt slowly, reviving at 

 night so that wilting is most evident in the middle or later part of the day. 

 The leaves turn brown gradually, and several days may elapse before the 



