20 



infection, but all over certain newly expanded buds. Careful 

 examination makes it evident that the buds were infected 

 before they had opened, and this implies that the mycelium 

 of the mildew entered the young soft bud during the pre- 

 vious autumn and remained in the bud in a dormant state 

 during the whole winter. This method of overwintering by 

 means of hibernating mycelium is rare amongst mildews, 

 but occurs also in the mildew of hawthorn, coppiced oak and 

 in that of the garden Euonymus. 



The infected buds as they open soon produce a crop of 

 spores, consequently the leaves and flowers early assume the 

 mildewed aspect and appear as white mealy rosettes (Fig. 1). 

 These mildewed rosettes, which arise exclusively from the 

 hibernating mycelium, are termed " primary " infections, and, 

 as it is from them that all later infection directly or indirectly 

 arises, it is clear that in seeking to eradicate the disease it is 

 of the utmost importance that they should be removed. 



The buds infected with hibernating mycelium are most 

 often fruit buds, either terminal or spurs, but wood buds, 

 especially terminals, are also invaded. The infected buds 

 can hardly be distinguished from the normal, but all shoots 

 showing the whitened appearance of the " wood " (Fig. 2), 

 recognisable even in winter, are liable to contain infected 

 buds and should in consequence be pruned away. If this 

 were done thoroughly the trees would be largely freed from 

 mildew, as little secondary infection (unless introduced from 

 neighbouring gardens or other trees) could arise. 



When the leaves only have been attacked and the " wood " 

 and buds have escaped infection, the mildew disappears with 

 the normal shedding of the leaf in autumn. 



Susceptibility of Varieties. The varieties most suscep- 

 tible to apple mildew are Lane's Prince Albert, Bismarck, and 

 Cox's Orange Pippin. In the Wisbech and Evesham districts 

 large plantations of the first two varieties may be seen com- 

 pletely ruined by mildew attacks. Amongst other varieties 

 which frequently suffer are Bramley's Seedling, Grenadier, 

 Irish Peach, Lord Grosvenor, Lord Suffield, and Mr. Gladstone. 

 Very frequently young stocks 2 or 3 years old, both in this 

 country and in America, are badly attacked by mildew, and in 

 some cases killed outright. 



Measures of Control. 1. Winter Pruning. Since the new 

 outbreaks commence each year from infected buds these latter 

 should, as far as possible, be removed. When pruning the 

 trees all shoots which were mildewed during the past summer, 

 and recognisable in winter by the white appearance of the 

 young " wood " should be cut away. The operation should 

 be carried out early, as if delayed beyond the new year the 

 distinction between the mildewed and the non-mildewed shoots 

 may be lost. 



