302 MAINE) AGRICULTURAL EXPERIMENT STATION. I907. 



In making bordeaux mixture, too frequently guess work is 

 substituted for weights and measures. There is also a tendency 

 to vary the proportions of the ingredients to a marked degree. 

 As low as 3 pounds of copper sulphate to 100 gallons of spray 

 and as high as 24 pounds to the 100 gallons were found to be 

 used, although these were exceptional cases. 



In view of these facts it seems well to supplement the direc- 

 tions for spraying which have been sent out by the Station 

 during the last dozen years, giving special emphasis to the 

 lessons which the experience of the last season has furnished. 



All power machines so far as observed met the requirements 

 with regard to the construction of pumps and nozzles, namely, 

 providing a constant high pressure and a fine, mist-like spray. 

 Nevertheless every type of sprayer so far seen in Maine potato 

 fields is inefficient as it comes from the manufacturers. Most 

 of them are only provided with a single nozzle to a row and, 

 when the foliage is full grown, can be raised but a few 

 inches above the top of .the row. This arrangement is sufficient 

 for the first and possibly the second spraying but should never 

 be used thereafter. Every spraying should mean the deposition 

 of a thin film of bordeaux on the surface of each leaf. Two 

 nozzles per row are necessary to accomplish this and 3 would 

 be better. These should be so arranged that they will evenly 

 cover the entire foliage of a full grown row. Where double 

 nozzles are used they should be farther apart than is commonly 

 the case, and if possible admit of some adjustment as to direc- 

 tion. It should be possible to raise the line of nozzles, as the 

 plants grow, to such an extent that each time the bordeaux is 

 applied the outer margins of the spray cones extend just beyond 

 the margins of the foliage of the row, thus giving uniform 

 protection to all leaves. It is with respect to the extent of this 

 adjustment that most machines are deficient. If a machine 

 does not meet these requirements it should be remodeled till it 

 does. Each leaf should be covered at each spraying regardless 

 of whether it takes 50, 100 or 150 gallons of bordeaux per acre. 



For late blight, spraying should ordinarily be begun from 

 10th to the 20th of July. If the weather is dry and sunny one 

 can wait until the latter date or even later, but if very moist, 

 cloudy weather prevails the former date is none too early. In 

 average seasons 4 and sometimes 3 thorough sprayings will be 



