1910.] PUBLIC DOCUxMENT — No. 31. 47 



products vary considerably as regards chemical composition. It 

 is imperative for manufacturers of spraying mixtures or other 

 remedial substances used on plants to demonstrate that their 

 products are thoroughly trustworthy before putting them on the 

 market. It is true that a spraying mixture can be used on one 

 crop safely and not on another. It is also known, as previously 

 mentioned, that meteorological conditions play an important 

 role in this connection. It is safer to spray when the sun shines 

 than during cloudy weather, for severe injury has often been 

 noticed from spraying with various fungicides and insecticides 

 in cloudy periods when no injury would have occurred had the 

 sun been shining. 



It is therefore important in. spraying that attention should be 

 given to the weather conditions, since if the spray is allowed 

 to remain on the foliage in a moist condition for too long a time 

 burning is likely to result. On the other hand, if the sun is 

 bright and the spray mixture dries on the foliage very quickly, 

 no such injury is likely to occur. 



Burning of maple tree foliage has also been noticed as result- 

 ing from spraying with arsenate of lead, at the rate of 13 pounds 

 to 100 gallons of water, and our attention has been called to a 

 nundier of cases of severe burning of beech trees sprayed with 

 this after standard formulas. 



