PEANUT DISEASES 309 



of the United States. This disease, then, is a potentially serious disease in 

 these regions. Rotation offers the only hope for large-scale control. There 

 is need for research to determine host ranges of the strains attacking pea- 

 nuts in order that rotation programs can be intiated. 



Nematodes and witches' -brooms on peanuts. In 1935 peanuts were 

 found in Tennessee with typical witches'-brooms and the nematode 

 Cephalobus elongatus cle Man. was isolated from them (5). In 1936 a 

 similar witches'-broom of peanuts was found in Texas. Isolations yielded 

 C. elongatus and Acrobeles crossatus Steiner. In the latter case it was 

 doubted that either nematode was the cause of the witches'-broom. 



Meadow nematodes and peanuts. Nematodes of the genus Praty- 

 lenchus Filipjev cause a general root destruction of many plants (138). 

 Little is known of the effects of these meadow nematodes on peanut roots, 

 but they do frequently attack pods, producing black spots and providing 

 points of entrance for secondary invaders. Steiner (138) has indicated 

 need for more work on these nematodes. This need is doubly evident for 

 peanuts because of the possibility of both root and fruit damage. 



Rhisoctonia on Older Peanuts 



There are references from almost all peanut-producing regions to 

 Rhizoctonia solani Kuhn on peanuts^*- While usually not stated, it ap- 

 pears that the primary concern is with seedling diseases. 



In the southeastern United States many peanut plants beyond the 

 seedling stage show typical dry, greyish or reddish-brown Rhizoctonia 

 cankers on stems near the soil. Although some cankered stems break off 

 in wind or during cultivation or dusting, few, if any, plants appear to be 

 killed as a result of this cankering. At maturity numerous greyish-blue 

 fruiting bodies on the "perfect" stage — Corticium solani (Prill, and De.) 

 Bound and Galz. — may be found on peanut stems in contact with the 

 soil. It may be that high temperatures during the growing season are the 

 important factor in making R. solani of little apparent consequence on 

 peanuts beyond the seedling stage. 



Possibly attacks of R. solani on the peg are an important factor in 

 harvest nut losses^®. At present any theory as to R. solani and diseases 

 of peanuts beyond the seedling stage is purely suppositionary. 



" See page 267 for section on seedling dry rot. 



*" See page 282 for section on soil rots of nuts and pegs. 



