A COMPARATIVE TEST OF LIME-SULPHUR, 

 LEAD BENZOATE AND BORDEAUX MIX- 

 TURE FOR SPRAYING POTATOES. ♦ 



F. C. STEWART and G. T. FRENCH. 



SUMMARY. 



This bulletin contains an account of an experiment designed 

 to test the relative merits of lime-sulphur (i to 40), lead ben- 

 zoate (i lb. to 50 gals.) and bordeaux mixture (6-6-50) for 

 spraying potatoes. The experiment included 20 rows of potatoes, 

 412 ft. long. Each of the three spray mixtures was applied six 

 times (at intervals of two weeks) to five rows and the remaining 

 five rows served as checks. " Bugs " were eliminated by making 

 two applications of lead arsenate over the whole field. The 

 spraying was done very thoroughly. 



There was no late blight, very few flea beetles and a very little 

 early blight, in October. Tip burn was the only disease of 

 consequence. 



In October the bordeaux rows were strikingly superior to all 

 others. They were larger, freer from tip burn and lived longer. 

 The lead benzoate rows were equal to the checks. The lime- 

 sulphur rows were plainly smaller than the checks and as badly 

 affected with tip burn. None of the mixtures burned the foliage. 



The bordeaux rows yielded 100.3 bu. per acre more than the 

 checks, lead benzoate 6 bu. less than the checks, and lime-sulphur 

 39.5 bu. less than the checks. 



The results indicate plainly that neither lead benzoate nor 

 lime-sulphur can be profitably substituted for bordeaux mixture 

 in spraying potatoes. Both lack the stimulative influence pos- 

 sessed by bordeaux while lime-sulphur also dwarfs the plants 

 and lowers the yield. 



INTRODUCTION. 



Within the past few years the lime-sulphur solution has largely 

 superseded bordeaux mixture as a summer spray for apple scab. 

 While probably as efficient as bordeaux in the control of scab it is 

 less liable to burn the foliage and russet the fruit. Many fruit 



*A reprint of Bulletin No. 347, March, 1912; for "Popular Edition," 

 see p. 830. 



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