33 



suffer more than others, as the pests flourish most in warm, 

 sheltered situations. 



The injury to the tree is caused by the loss of sap which 

 is sucked up and devoured by the pests. In a bad case, where 

 the branches are completely encrusted with scales, the tree 

 suffers so severely that it may die in part if not altogether. 

 Old trees are more often infested than young trees, but at the 

 same time they are able to withstand the attack better, and 

 when by bad management, a young plantation is allowed to 

 become badly infested, the damage sustained may be irrepar- 

 able. Since Mussel Scales are to be found in small numbers 

 in practically every apple orchard, a careful watch should 

 always be kept so that if any increase in the numbers of the 

 pest is noted, control measures may be taken before serious 

 harm has resulted. . 



Natural Enemies. Mussel Scales are devoured by Tits 

 and probably also by the Tree Creeper and Wryneck. They 

 are attacked by certain minute parasitic insects (Chalcids) 

 which, however, are not a sufficient check on the pest to 

 render artificial measures of control unnecessary. 



Control Measures. (1) In the case of a bad attack, the 

 trees or bushes should be sprayed when dormant (November 

 to February) either with an oil emulsion or with Woburn wash 

 (see Leaflet No. 70). There are now on the market several 

 makes of oil which mix (or form an emulsion) with water, 

 and if used they should be diluted in the proportions recom- 

 mended by the makers for a winter .wash. A home-made* 

 emulsion for winter use may be mixed as follows: 



Paraffin oil ... ... ... ... 1 gall. 



Soft soap l-2 Ib. 



Water 10 gall. 



The soap is first dissolved in' about a gallon of boiling 

 water. The soap solution is then removed from the fire, and 

 the paraffin is at once added, the whole being emulsified by 

 squirting the liquid back into itself with a hand syringe. 

 The strong emulsion may be kept until required for use, when 

 the remaining nine gallons of water should be added and the 

 whole thoroughly stirred or better, emulsified again with 

 the hand 'syringe. 



Oil emulsions, whether bought or home-made, must be 

 applied carefully so as to wet every portion of the tree, not 

 forgetting the undersides of the large branches. The eggs 

 under the scales will be killed only where the scales them- 

 selves are thoroughly wetted, and if a few escape the trees 

 will be re-infested. 



(2) In America' good results have been obtained .by the 

 use 'of lime-sulphur washes, and although in England lime- 

 sulphur has proved rather disappointing in the case of bad 



