INSECTICIDES AND FUNGICIDES 



255 



for San Jose* scale to use one part of the solution to eight or ten of water 

 and to apply during open weather in February or March, while the trees are 

 still dormant. For summer use they must be diluted with from 30 to 50 

 parts of water to avoid injury to the foliage, but lose much of their value 

 as insecticides when thus weakened. The concentrated solution is regarded 

 as the most effective remedy for scale injury now in use. 



It should be added that there has somewhat recently appeared a 

 so-called "soluble sulphur" which is recommended for the same uses as 



A LIME-SULPHUR COOKING OUTFIT.* 



lime-sulphur. It promises well, but has not been tested long enough and 

 carefully enough to justify very positive statements as to its merits. 



Tobacco Extracts. For use against soft-bodied insects such as plant 

 lice there is no more useful insecticide than extracts made from the midribs 

 of tobacco leaves. These extracts contain as their effective ingredient 

 nicotine and differ widely in the percentage of nicotine they contain. 

 Home-made extracts or decoctions are made by placing a couple of pounds 

 of the midribs in a wooden bucket full of boiling hot water, allowing it to 

 stand over night. The percentage of nicotine under such treatment will 

 probably not be more than 0.07 per cent, but it is a very useful wash for 

 plants infested with aphides, does no harm at all to leaves, and where 



From Farmers' Bulletin 650, U. S. Dept. of Agriculture, 



