150 TWENTY-FIFTH ANNIVERSARY Report. 
interest in the experiments and the number who practice spraying is 
rapidly increasing. No doubt the recent improvements in potato 
spraying machinery have had much to do with the advance of 
potato spraying. ‘There are now upon the market several thor- 
oughly practical horse power sprayers for potatoes. 
In addition to the spraying experiments above described studies 
and experiments have been made on closely related subjects. For 
example, in 1904 and 1905 a mixture of sal soda, copper sulphate 
and water, called soda bordeaux, was compared with the regular 
bordeaux mixture as a preventive of potato blight. The regular 
bordeaux gave slightly better results in both seasons.146 
Another of these experiments was a comparison of warm and cold 
water for making bordeaux mixture to spray potatoes.” Some 
persons held the opinion that bordeaux mixture prepared with cold 
water, such as comes from deep wells, is injurious to potato foliage. 
The results of the experiment showed this opinion to be without 
foundation in fact. 
A third line of investigation was on the effect of certain arsenites 
upon potato foliage.“5 It had been claimed by some that arsenical 
compounds are injurious to the potato plant even when applied with 
properly made bordeaux mixture. Inasmuch as paris green and 
arsenite of soda, the leading insecticides used on potatoes, are both 
compounds of arsenic it was deemed advisable to look into the 
matter. The chief conclusions reached were: 
(1) That paris green is not injurious to potato foliage if ap- 
plied in moderate quantity with lime water or bordeaux mixture 
evenly distributed ; 
(2) That paris green possesses considerable value as a preventive 
of potato late blight ; 
(3) That arsenite of soda is much less liable to injure the foliage 
when used with bordeaux than when used with lime water even if 
the same quantity of lime is used in both cases. 
Analyses of sprayed and unsprayed potatoes showed the former to 
contain a larger percentage of starch;'” and a test of their cooking 
qualities showed the sprayed potatoes to be much the more mealy.’ 
“ Bul. 264:187-194; same in Rpt. 24:177-183. 
Bul. 279:215; same in Rpt. 25:174-176. 
™ Bul. 279:222; same in Rpt. 25:180, 181. 
** Bul. 267 (1905) ; same in Rpt. 24:195-214; see also Bul. 279-217. 
 Buls. 221:253; 241:265: 2647174 
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