Eradication of Scale Insects. 



53 



Lime Mixtures for the Eradication of Scale Insects. 



During the course of experiments carried out in the winter 

 of 1898-9, at the Central Experimental Farm at Ottawa, 

 Canada, in whitewashing apple-trees, it was noticed, when 

 the whitewash came off in the summer, that the trees, which 

 had been previously infested with the oyster-shell bark louse 

 [Mytilaspis pomorum), were practically free from the insect. 

 Attention having thus been directed to the point, experiments 

 were planned to discover how tar this oyster-shell bark louse 

 (or mussel scale, as it is usually called in England) could be 

 eradicated by this means. 



Infested trees were accordingly sprayed four times, in 

 November and December 1899, with a mixture of lime and 

 water in the proportion of 2 lbs. of lime to one gallon of 

 water. The results obtained are considered to have been 

 very convincing. It was not necessary to add anything to 

 the mixture for the purpose of making it stick better to the 

 tree, as the loosening of the scales by tlie lime occurs within 

 the first two weeks after the application of the mixture, for 

 the wash was cracking off badly within ten days after the 

 trees received the application. It also appeared from the 

 experiment that two sprayings were sufficient to give satis- 

 factory results. 



These tests indicated that it was the caustic property of 

 the lime, which had been the means of loosening the scales, 

 and further experiments were planned to determine the 

 minimum strength of lime, the number of sprayings, and the 

 time of year to spray. These were carried out in March last 

 year, with rather conflicting results. One conclusion to be 

 drawn, however, was that autumn, and not late winter or spring, 

 was the best time to spray the trees for this purpose in Canada. 

 As large a proportion of scales appear to have been removed 

 by the thinnest washes (1 lb. of lime to a gallon of water) as 

 by the thickest, and it would seem that the thicker and stickier 

 mixtures had the effect of glueing the scales to the trees, thus 

 counterbalancing to some extent the action of the lime in 

 loosening them. 



No injury was caused to the trees themselves ; and the 



