10 Jan., 1919.] Apple Culture in Victoria. 31 



of the branch system. But, when sections of the bark, cambium, and 

 young wood of the roots beneath them are destroyed by the larvae, the 

 pressure is probably relieved, as, during the periods of growth, the 

 wounded parts exude liquid matter. One of the functions of the 

 root caps and the bark is to maintain the purity of the sap, which 

 probably becomes contaminated during the process of absorption by 

 soil acids and possibly deleterious bacteria entering through the 

 wounds. 



Certain varieties, like Rome Beauty, Yates, &c., do not show the 

 effects of borer for a considerable time, while others, such as Jonathan, 

 London Pippin, &c., collapse after a relatively short period of infec- 

 tion. This may be attributed chiefly to the influence of scion on 

 stock. "When the main roots of the Rome Beauty,. Yates, &c., be- 

 come so seriously damaged as to prevent sap movement, tufts of 

 small roots are produced at the points above the wounds, and these 

 supply much of the necessary nutriment. Occasionally the main roots 

 of the Jonathan, London Pippin, &e., produce a few fibrous ones in 

 the manner described, but the influence of these varieties on their 

 stocks is not sufficient to induce the growth of enough of these 

 £brous roots to sustain the trees. Although much has been done by 

 the orchard supervisors and others interested in the suppression of 

 this pest to clear up its life history, the length of time involved in 

 the larval stage is still unknown. Its ravaging propensities call for 

 more effective remedial measures than those at present employed, and 

 here is a wide field for further investigation and experiment. These 

 should include fighting the borer with its natural parasite (Perilitus 

 leptopsi, Viereck), discovered by Mr. H. W. Davey, orchard super- 

 visor. 



"Woolly Aphls (Eriosema lanigera). 



Of the apple pests which live by suction there is none more widely 

 distributed, destructive, and difficult to keep in check than woolly aphis. 

 Every part of the tree which is not blight-proof is liable to be attacked, 

 but the roots are noAv protected by the employment of resistant stocks), of 

 which l^orthern Spy is in most general use. The work of controlling 

 the blight was much more difficult when non-resistant stocks were used, 

 because, no matter how free the branch system was kept, the insects on 

 the roots, as well as weakening the tree, afforded a sure source of con- 

 tinual infection. 



The presence of woolly aphis in an orchard is usually first indicated 

 by the appearance of a small number of the insects on the soft bark of 

 the succulent young growths, on the callousing bark of the amputation 

 marks on the leaders, laterals, and spur growths made by the secateurs 

 at the last pruning operation, or on the bark wounds of the stems and 

 main arms caused by swingle-bars, or through the careless handling of 

 cultivating implements. The matured bark being impenetrable, the 

 insects insert their probosces in the young soft rind and suck out the 

 juices on which they live. Usually when the first infection is of a serious 

 nature, the laterals of the current year's growth are attacked. "Weather 

 conditions continuing favorable, the insects multiply rapidly, and fprm 

 colonies on the underneath side of the laterals. When spraying treat- 

 ment is neglected during the first year of infection, and the colonies of 



