POTATO SPRAYING AND DUSTING. 3 



The use of sulphur in these experiments marks an innovation in the apphcation 

 of this material as a fungicide of potato-leaf diseases, in this State at least. In 

 Europe, especially Southern France, and in Algeria, sulphur has been extensively 

 used in combating Oidium and other fungous diseases of the grape vine with most 

 encouraging results. Of the various forms employed ground sulphur has shown 

 itself superior to sublimed, wind-blown and precipitated sulphur in its anticrypto- 

 gamic properties. This is accounted for by the fact that it is said to contain neither 

 sulphuric nor sulphurous acids which burn the leaves under the influences of great 

 heat. Again the finely divided condition of ground sulphur is a factor of importance 

 bearing on its fungicidal capacity, to which may be added the further advantage of 

 its lower cost of production. Neutral mixings, according to Bourcart,* have a much 

 more gentle action on the leaves, therefore mixtures of sulphur with gypsum and lime 

 are generally employed, which, moreover, favour adherence in rainy weather. 

 According to this same author (he. cit. p. 46) sulphur has also a direct action on the 

 grape vine, which it renders more vigorous. That this is probably true also of 

 potato foliage under certain circumstances is shown by the results obtained at Elmer 

 on the blocks dusted with a mixture of sulphur and lead arsenate. These yielded 

 21 bushels per acre more potatoes than those treated with arsenate of lead 

 alone. This was, however, but a third of the increase derived from the use of 

 Bordeaux and lead arsenate mixture. 



A series of experiments carried out by Bourcart {loc. cit. p. 46) showed that sulphur 

 was effective as a fungicide between the temperatures of 77°-122° F., not in virtue of 

 the supposed generation of sulphur dioxide or sulphuretted hydrogen, but by reason 

 of its own vapours. But it was my experience that applications of sulphur made in 

 the heat of summer (95° F.) may cause injury to the leaves, which are burned under 

 the action of the sun. 



The comparative aspect which this year's experiments are intended to bear out 

 must not be lost sight of, and the differences in yields obtained on the differently 

 treated plots are worthy of strict attention. Besides the fact that the home-made 

 Bordeaux mixture gave the best return as regards yields in all three experiments, 

 it also proved to be the most economical in application, excepting the lead arsenate 

 used on the control plots at Freehold and Elmer and intended only to check the 

 ravages of the Colorado and flea-beetles. 



The experimenters at Geneva, New York, have also come to the conclusion that 

 there are several factors which might have an important influence on the results. 

 Amongst those are mentioned differences of locality and soilsf. The averages for 

 the ten-year experiments at Geneva and Riverhead reveal the fact that the average 

 increase for sprayed potatoes per acre at the former is more than double the increase 

 at the latter. At Geneva the soil is rather a heavy clay loam, at Riverhead a sandy 

 loam, which is interesting in view of what has been said about the experiments at 

 Freehold, New Jersey. Sheltered rather than exposed conditions give better results, 

 and in the final reckoning up the fertility of the land and the variety of the potato 

 are factors of no mean importance. But probably, as the author remarks, most 

 attention must be paid to thoroughness in spraying. 



* Bourcart (E.). — Insecticides, Fungicides and Weed- Killers. London, 1913. p. 45. 

 t Stewart (F. C.).— Bull. 290, N.Y. Agr. Exper. Sta., 1907, 

 (C155) A 2 



