■116 THE PEANUT— THE UNPREDICTABLE LEGUME 



As shown by studies in Georgia (172), the most logical means of pre- 

 venting spread of infection, is the application of fungicides which kill 

 conidia on leaflets before they germinate and penetrate leaf tissue. Tests 

 in Virginia (94) have indicated that plants so protected lose a lower 

 percentage of nuts in the soil before digging, lose a lower percentage of 

 nuts at digging, and have a greater total yield. Similar results, particu- 

 larly in regard to total yield, have been obtained in Alabama (165). 



Results suggesting that fungicidal applications sometimes influence 

 the number of nuts left on the vine rather than total yield have been ob- 

 tained in Florida. When the nuts left in the soil were added to the har- 

 vested yield there was no appreciable difference in total yields between 

 control and check plots (20). However, this pubHcation cited the unpub- 

 lished results of other control tests in Florida carried on over a period of 

 5 years and these other tests indicated a 1 5 to 20 percent increase in yield 

 of harvested nuts. Also, the weather of the particular year in which these 

 experiments were made was conducive to leafspot so that no correlation 

 was evident between treatment and leaf-spot control. 



Various fungicides have been tested as dusts and sprays (94, 165, 

 172). Pending further testing of newer fungicides it seems that either 

 sulfur or 10-90 copper-sulfur with the mixture containing the equivalent 

 of about 3.5 percent metallic copper are to be recommended as dusting 

 materials. Spraying with Bordeaux (6-2-100) gives satisfactory control 

 but is no better than dusting. 



The following general recommendations for procedure in dusting for 

 leafspot control have been modified from Woodroof et al. (172) after 

 checking for agreement with Miller (94) and with Wilson and Arant 

 (165): 



1. Practice rotations of fields to peanuts at 3-year intervals. Maintain 

 vigor of plants by fertilizer, cultivation, etc. 



2. Dust with conditioned dusting sulfur (at least 93 percent through 

 325 mesh) or copper-sulfur 10-90 (34 percent basic copper sulfate 10 

 parts, dusting sulfur 90 parts). 



3. Begin dusting about 90 days after planting. 



4. Apply dust every 10 to 14 days. If rain occurs within 24 hours 

 after first dust, repeat after 7 days. If rain occurs within 12 hours after 

 later dusts, repeat dusting as soon as possible. Continue dusting to within 

 14 days of harvest. Three to five applications usually are required. 



5. The size of the vines determines to a considerable extent the 

 amount of material required for coverage; 12 to 15 pounds per acre of 



