124 



and lives within the tissues of the leaves 

 and continues to develop during the vi^in- 

 ter, producing its fruiting bodies which 

 shed spores on the flowers and young 

 leaves as they unfold. 



The most certain method of dealing 

 with this disease is to collect and burn the 

 dead leaves before the young foliage un- 

 folds ; this has been found to be both 

 practicable and effective. Spraying the 

 young leaves with Bordeaux mixture will 

 check the disease, and this method should 

 be employed where scarcity of labour ]Dre- 

 vents the carrying out of the first method 

 of control. 



Peach Leaf Curl. 



This disease, familiar to most growers 

 of peaches, is characterized by the 

 abnormal character of the affected leaves, 

 which are thick, fleshy, curled, and 

 wrinkled (See Fig. 9) ; they are paler than 

 the healthy leaves, often yellowish or red- 

 dish, and become covered with a grey or 



Fig. 9.— a peach leaf attacked by the leai curl 

 fungus, Exoascus deformans. 



whitish bloom. The fungus Exoascus 

 deformans, growing within the tissues of 

 the leaves, eventually develops its fructi- 

 fications in a thin layer covering the 



epidermis, and the spores liberated from 

 these fructifications serve to reproduce 

 the disease on other leaves. Finally, the 

 affected leaves are killed and fall off 

 before the normal time, and, when serious 

 defoliation occurs, the vigour of the trees 

 is impaired; the crop in consequence 

 suffers in quality and amount. The 

 fungus also extends into the young shoots, 

 which, as a result of the infection, become 

 somewhat swollen and stunted. 



To control this disease infected shoots 

 should be pruned off and burnt, and the 

 trees should be thoroughly sprayed with 

 a fungicide in winter before the buds 

 open; for the latter purpose Bordeaux 

 mixture (6:6:50), Burgundy mixture or 

 lime-sulphur (concentrated solution sp. 

 gr. 1.3 diluted 1 in 15) may be used. 

 Crown-Gall. 



A disease which has hitherto received 

 little attention in this country is one 

 which is of interest to the practical fruit 

 grower from the fact that young fruit 

 trees are liable to infection, nursery stock 

 in particular often becoming affected. 

 The disease is similar to one which is 

 common in America, and has been under 

 investigation in the United States for a 

 number of years; it was found to be 

 caused by an organism which has been 

 named Bacterium tuviefaciens. Crown- 

 gall is known to occur in this country on 

 the apple, pear, plum, rose, raspberry, 

 and loganberry. 



The galls are usually produced at the 

 base of the stem just below the ground 

 level, but they also occur on the roots at 

 some distance below the level of the soil ; 

 they are therefore not visible until the 

 tree is uprooted. They are irregular out- 

 growths, frequently of some considerable 

 size, and when occurring on the stem itself 

 may be several inches in diameter. 

 Eventually they slowly disintegrate and 

 the organisms are set free into the soil 

 which thus becomes contaminated. 



When the grower is planting up fruit 

 trees he should examine them carefully 

 and reject all those which are affected 

 with these abnormal growths. Where 

 nurseries are infested with the disease the 

 owner should endeavour to raise young 

 trees free from the disease by starting 

 with clean stocks in ground where crown- 

 gall has not previously occurred. 



