LIME-SULPHUK DWARFS POTATO PLAXTS.-^ 



F. H. HALL. 



Linie-sulpliur solution can not rcpluec bordeaux 

 Bordeaux mixture as a preventive of potato diseases. Or- 



best for chardists who also grow potatoes hoped that they 



potatoes. might use the lime-sulphur spray in the field as 



well as in the orchard and dispense with the bor- 

 deaux altogether, as it would be convenient to prepare only one 

 fungicide; but a careful test made at this Station in 1911 proves 

 the lime-sulphur harmful to potatoes. The plants in rows sprayed 

 with lime-sulphur were dwarfed by the fungicide, died early and 

 yielded about 40 bushels less to the acre than plants in check rows ; 

 while the bordeaux-sprayed rows produced 100 bushels to the acre 

 more than the checks. 



The first row of each of five series was left as a 

 The check, the second row received bordeaux mixture 



test. (6-6-50), the third lime-sulphur solution (1 to 



40), and the fourth lead benzoate (1 lb. to 50 

 gals.). Each treatment was repeated six times, as the season was 

 a long one, and all the rows were kept free from beetles by two ap- 

 plications of lead arsenate. 



The dwarfing efi'ect of the lime-sulphur was plainly evident by 

 September 16 and became very noticeable in October. The plants 

 were really smaller than those on the check rows, not merely ap- 

 pearing smaller through lack of foliage; for the stems were both 

 shorter and of less diameter on the lime-sulphur rows. The lead 

 benzoate plants were not dwarfed, but their condition was no bet- 

 ter than that of the checks. There was no apparent burning of the 

 foliage on any of the rows. 



Parasitic diseases were comparatively harmless, as there was 

 only a little early blight (very late in the season), and no late 

 blight ; but tip-burn seriously affected the plants of all rows except 

 those sprayed with bordeaux, and injured even these somewhat, es- 

 pecially toward the north end of the field. The bordeaux-sprayed 

 rows were still partly green when frost came, October 27, while 

 most of the plants on the other rows had been dead a week or more 

 at this time. 



The long season gave the bordeaux the best possible opportunity 

 to exert its stimulative influence, and the thorough spraying may 

 have intensified the injury from the lime-sulphur; so that the test 

 probably presents lime-sulphur in its most unfavorable light. As 

 a whole, however, the experiment conclusively proves it unsafe to 

 use lime-sulphur on potatoes and unwise to consider lead benzoate 

 as a fungicide for potato diseases. 



* A reprint of "Popular Edition" of Bulletin Xo. 347; see p. 193 for the 

 Bulletin. 



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