104 



American Gooseberry Mildew. [may, 



measures in length from 10 to 13 mm., and in span of wings 

 from 14 to 15 mm. The larvae are white with small rounded 

 horny heads; the legs are weak. The larvae have a great 

 resemblance to those of Sir ex, but there are only nine stigmata 

 on each side ; there are differences, too, in the head and in the 

 shape of the spine at the end of the body. 



Life-history.— female, by means of the ovipositor, bores 

 into the bark, laying an egg in the outside of the wood. In the 

 elm, the larva was found on hatching to eat out first of all a 

 vertical gallery and then abruptly to tunnel in the transverse 

 direction, turning later towards the bark, below which pupation 

 took place. 



R. Stewart MacDougall, 



The Board have already issued memoranda* on the subject 

 of the American Gooseberry Mildew (Sphaerotheca Mors-uvce, 

 Berk.), with suggestions for the pre- 

 American Gooseberry vention and remedy of the disease. A 

 Mildew. description of the disease may now be 



given which will enable fruit growers to 

 recognise it if their gooseberry bushes are found to be attacked. 



This fungus is much more injurious than the allied English 

 Gooseberry Mildewf (Microsphczra Grossularice , Lev.), as it 

 not only attacks the leaves, but also extends to the shoots 

 and fruit, stunting the latter and rendering it unsaleable. 

 The disease usually first appears as a delicate white mildew 

 on the expanding leaf-buds, extending later to the young 

 wood and fruit. During the summer months enormous 

 quantities of the spores are produced, these spores spreading 

 the disease by being conveyed from infected to healthy shoots 

 or adjoining bushes by wind, rain, insects, &c. At a later 

 stage the patches of mildew gradually change from white 

 to a dingy brown colour, and become densely studded with 

 the winter fruit, which appears in the form of very minute 

 black dots. The spores contained in the winter form of fruit 

 germinate the following spring, and give origin in turn to the 

 white summer mildew. 



* See Journal, December, 1906, p. 560 ; and April, 1907, p. 44. 

 t See Leaflet No. 52 (Gooseberry Mildew). 



