174 Insect Pests. 



the scales to turn grey, partly corrodes them away, and penetrates- 

 under the scales, and so destroys the eggs. We should use this- 

 as a winter wash, when it is less likely to do any harm, there always- 

 being a risk of damage to the trees when paraffin emulsion is- 

 used in summer. Of the 2,000 trees treated, six were said to be 

 killed, and ten badly damaged. These were all around the tanks- 

 where the wash was prepared, and it is probable that the first few 

 pailfuls of wash were not properly mixed, and then the trees had 

 an extra dose of paraffin. This may or may not be so, but according 

 to the men working in the plantation the death was mainly due to old 

 and repeated canker. 



" The effect on the bark of some trees was very marked, peculiar 

 irregular cracks being formed, but none of these trees have been 

 damaged, and have blossomed well. The weaker mixture was found 

 sufficiently strong to kill this pest, and for summer work it is the better 

 to use. 



"Two trees were sprayed with pure paraffin in the winter, in 

 neitlier case was any damage done to the tree, and all the scale was- 

 destroyed." 



The experiments conducted by Furley (3) in Worcestershire point 

 to three washes being successful in killing the eggs, namely, caustic 

 alkali wash, paraffin emulsion, and the Woburn wash (7). The- 

 latter and the alkali wash worked more rapidly than the emulsion, 

 but the former is undoubtedly harmful to the trees. 



Lime-salt -sulphur wash had been previously experimented with,, 

 and was not tried again at Mr. Amos' as the paraffin treatment 

 seemed to be the most successful. But Mr. Paget-Norbury writes- 

 from Malvern that he has found this useful, quite 50 per cent, beino- 

 killed by it (6). 



In conclusion, we may say that for Mussel Scale in the egg stage,. 

 or when the females are completely protected by their brown covering, 

 the employment of paraffin emulsion or the Woburn wash is the 

 most successful method of treatment. In winter the strong mixture 

 of emulsion may be used, up to 7 or 8 gallons of paraffin per 100- 

 gallons of wash being necessary ; in June it was found that it had 

 some, but not much, ill effect upon the bark ; the weaker solution 

 had not, and thus this should be used when there is a bad attack 

 in summer. Somewhere about the first week in June tlie scale- 

 insects hatch out, and then, if present in only small quantities, they 

 may be held in check by spraying all the tree with soft soap and 

 paraffin (10 lbs. of soap, 2 gallons of paraffin to 100 gallons of water), 

 or even soap and quassia. 



