202 JOURNAL OF ECONOMIC ENTOMOLOGY [Vol. 4 



SPRAYING WITH LINSEED OIL WASH FOR THE OYSTER- 

 SHELL SCALE 



By R. L. Webster 



At the Boston meeting of this association Prof. R. A. Cooley read 

 a paper giving the results of tests of several spray materials for the 

 oyster-shell scale. One of the most promising of these was a linseed 

 oil emulsion. The writer has been trying a number of materials 

 against this scale in Iowa, but with no success, and so this linseed 

 oil wash was given a trial last spring. 



Professor Cooley 's formula, which I used, is given herewith: 



Hard soap 1 pound 



Raw linseed oil . 1 gallon 



Water to make 12 gallons 



The soap was dissolved in a small quantity of water and an emulsion 

 was made with the oil. This was diluted while warm to the required 

 strength. 



The mixture was used during the hatching period of the insect, 

 which was long drawn out last spring. One spraying was made May 

 13 and another May 18, in a badly infested orchard at Ames. Both 

 sprayings were very effective; far better than the lime-sulphur wash 

 or any other mixture that I have tried. 



The linseed oil wash adhered to the trees very well. It was still 

 conspicuous as late as July 22. There was no injury to the leaves; 

 in fact, the foliage was in excellent condition all summer. The season 

 was exceptionally dry. 



The young scale insects were plentiful on the trees when they were 

 sprayed. The spray . evidently killed most of the young which had 

 settled down and it also prevented others from establishing them- 

 selves on the bark. Very few live insects were found on the sprayed 

 trees later in the season. The earher spraying, that of May 13, 

 seemed to be slightly more effective than the later one. 



From time to time unsprayed trees in an orchard just across a 

 railroad track were compared with the sprayed trees. The unsprayed 

 trees were badly infested, like the sprayed trees. Living scales 

 were very numerous during the late spring and summer on the un- 

 sprayed trees, while a hve scale was found only here and there on the 

 sprayed trees. 



The cost of this hnseed oil wash is a serious drawback on its use. 

 Raw linseed oil has been quoted to me F. 0. B. Des Moines at $1 a 

 gallon in 10-gallon lots, or 97 cents a gallon in 50 or 100-gallon lots. 

 At this rate the mixture would cost about nine cents a gallon. 



