246 
Hop Cultivation. 
air in a triumphant manner, and devours them with marvellous 
speed. Being without eyes, it makes sweeping motions on 
every side with its head, and nearly the whole of its body, as 
shown in fig. 9, in order to find aphides near to it. The quantity 
of aphides consumed by one of these larvae is extraordinary. It 
clears a hop leaf in a few minutes, and proceeds to another. 
Yet specimens of these have been sent to the writer with the 
suggestion that they were new foes of the hop plant. The larva 
of a kindred fly termed Syrphus balteatus is also useful, but is 
not so generally found in hop plantations. It may be stated 
here that the larva of Syrphus pyrastri will eat almost every 
kind of aphis, and was found in exceeding quantities last year 
(1892) upon wheat plants infested with Aphis grdnaria. 
Mildew. 
Mildew, or mould, as it is usually termed by planters, is 
frequently a serious scourge, which not only reduces the crop 
but materially damages its quality, and there is not at present 
a remedy for it that is perfectly efficacious. 
Mildew is caused by the action of a fungus, styled scientifi- 
cally Sphcerotheca castagnei or Podosphcera castagnei, belonging 
to the group of fungi known as Ascomycetes, and to its division of 
Erysipheae, according to De Bary’s classification. 1 The vine 
mildew, Oidium Tuckeri , which causes much harm in French 
and German vineyards, also belongs to the group of the Erysiphse, 
but this must not be confounded with the other fungus, Peronospora 
viticola , far more injurious to vines than Oidium Tuckeri. 
This fungus is propagated by germs, or spores, carried in 
the air to the hop plants, upon which they speedily germinate, 
sending haustoria, or suckers, through the epidermis of the 
leaves. De Bary shows that the conditions necessary for the 
germination of the spores are pretty much the same as for seeds, 
namely, a certain temperature and a supply of oxygen and 
moisture. When the spores find congenial hosts, liyphae are put 
forth, forming the mycelium, an aggregation of white threads, 
which appears upon hop leaves attacked by the mildew. Haus- 
toria from the mycelium permeate the tissues of the leaves and 
live upon them. 2 Much harm is not, however, occasioned by 
the fungus upon the leaves, but when the burr, or incipient cone, 
begins to form, it is frequently infected at once by the spores of 
1 Vcrgleichende Morphologie und Biologic dcr Pilze. Von A. De Bary. 
1884. 
2 The hop fungus, Podosj/licrra castagnei, is epiphytic, that is, it lives upon 
the plant and not within it, as the endophytic potato fungus, for example. 
