28 



Distribution. This insect is always more or less abun- 

 dant in old and neglected orchards and apple plantations 

 where no attention is given to pruning or to keeping the trees 

 free from moss, lichens, &c. Unfortunately it is also some- 

 times seen in orchards recently planted owing to nursery stock 

 being frequently sent out with aphis on the plants. Indeed, 

 although dispersal by the agency of wind is not unimportant, 

 by far the most common way for the pest to be distributed 

 is on infested nursery stock. Not only has the woolly aphis 

 been carried from orchard to orchard in Britain in this way. 

 but also from country to country, until it is now found in every 

 part of the world where apples are grown. It has been stated 

 that this aphis, although termed the American Blight, was 

 originally a European insect, but it is doubtful whether its 

 country of origin has yet been conclusively settled. 



Injury Caused. All varieties of apple in this country are 

 subject to the ravages of woolly aphis, but perhaps the old 

 Eibston Pippin suffers most of all. The Blenheim Orange, 

 Cox's Orange Pippin, and Lord Sufiield also suffer severely. 

 Varieties having a soft bark are most affected. Certain experi- 

 ments conducted in Victoria and elsewhere show that in the 

 case of apples grafted on Majetin and Northern Spy stocks 

 the roots are free from attack. 



Infestation may be on the main trunk, on the branches, on 

 the fruit, or on the roots; in very bad attacks the leaves are 

 also infested. The fact that the woolly aphis lives below 

 ground on the roots should be carefully noted, as the above- 

 ground parts, though cleared of the insect, may receive 

 a new infection as a result of migration from below. 

 That this migration from the roots actually takes place may 

 easily be proved by grease banding the trees, when the aphides 

 may be caught in large numbers as they ascend the trunks. 



The woolly aphis feeds, like all aphides, by puncturing the 

 epidermal tissue and then draining away the sap by means 

 of its proboscis. Not only is the tree weakened, but swellings 

 or galls result which later on crack, an appearance being pro- 

 duced (Fig. 4) resembling the lesions caused by the canker- 

 fungus. Sheltered in the canker- like cracks, the aphides are 

 more difficult to reach by treatment. The wounds produced 

 by the aphis ,are also said to serve as points of entry for the 

 true canker fungus (Nectria galligend.) (See Leaflet No. 56.*) 



Description and Life-History. The woolly aphis may 

 readily be recognised in an orchard by the masses of white 

 woolly substance formed by the larvae and females which are 

 sheltering in the crevices of the bark. The woolly substance 

 arises as an excretion from glands in the backs of both the 

 young and mature females. It may often be seen hanging 



* To be obtained from the Ministry, also included in Sectional Volume 

 No. 1, price 8d. 



