31 



of the trees. In all cases, however, success depends on the 

 thoroughness with which the treatment is carried out. 



(4) For a summer spray nicotine and soft soap, dilute 

 paraffin emulsion, or quassia and soft soap have all been 

 recommended. If used they must be applied with force and 

 the affected parts thoroughly drenched owing to the necessity 

 of penetrating the woolly material before the insects them- 

 selves are reached. 



(5) To prevent the introduction of the aphis, great care 

 should be taken to see that all young stock is clean before 

 planting. If any traces of either the root or the aerial forms 

 are seen, the trees should be returned to the nurseryman 

 to be disinfected before being planted. All nursery stock can 

 be fumigated with hydrocyanic-acid gas (see Leaflet No. 188*), 

 and thus thoroughly cleared of woolly aphis before planting. 



THE MUSSEL SCALE. 



(Mytilaspis pomorum, Bouch6.) 



The Mussel Scale is one of the most abundant scale insects 

 in the British Isles ; it also occurs on the Continent of Europe, 

 in North America, South Africa, Australia and New Zealand, 

 having been introduced into the three last countries on 

 infested nursery stock. As a pest the insect is most con- 

 spicuous in neglected apple orchards, but it is always present 

 on apple and certain other trees in all the fruit-growing 

 districts in the kingdom, and wherever it is allowed to increase 

 unchecked is likely to cause serious damage. In America it 

 is regarded ais an insect of considerable importance to apple 

 growers and is there known as the Oyster- Shell Scale from 

 its resemblance in shape to American oysters. 



Description and Life-History. The Mussel Scale lives on 

 the stem and branches, and occasionally on the leaves and 

 fruit of the plants, such as the apple, which it attacks. If a 

 branch infested by this insect be examined, it will be found 

 that the surface of the bark is more or less covered by small 

 brown objects (Fig. 1) about J inch in length, which are shaped 

 somewhat like a mussel shell. Each mussel-like scale forms a 

 roof or covering over the living insect during the summer, and 

 over its eggs in winter. 



The winter is spent in the egg stage, the eggs exceedingly 

 minute and like a whitish dust lying underneath the scales. 

 At the end of May or early in June very small wingless, louse- 

 like insects (larvae) are hatched from the eggs and crawl from 



* Obtainable from the Ministry. 



