Hop Cultivation. 
247 
the fungus from the leaves, which fasten upon its stalk and the 
bases of the forming bracts, and stop its growth, so that it 
ultimately shrivels up. Or the fungus attacks the fully-developed 
cones on their stalks and the bases of the bracts where there is a 
good supply of sap, reducing them to decay in a short time. 
After a while the whiteness of the mildew becomes brown 
from the formation of perithecia, or cases containing an ascus, 
or bag of eight spores, upon the mycelium. The spores remain 
in the bag until circumstances favour their further development. 
De Bary points out that this period of rest coincides with periods 
of vegetation and seasons in many fungi of this group, and it 
may be assumed that the resting spores of the hop mildew are 
dormant during the winter, as in the case of the rose mildew, 
Pod.osplicera pannosa , resting in the asci or bags, upon dead hop 
leaves and bines, or upon the pieces of bine left on the stocks, 
or on weeds, such as groundsel, so prevalent in hop grounds, 
plantain, dandelion, and others, or upon the ground . 1 The asci 
may be carried in the air to the hop plants in the spring, and, 
bursting, deposit their spores upon the leaves. After these have 
established mycelia, or centres, continuous generations of spores 
will be discharged if the surroundings are favourable, and con- 
veyed by breezes to infect other plants. As is well known to 
planters, in some seasons mould does not “ run : ” that is, in- 
fection is not continued, from climatic influences, or other 
reasons that have not been determined. White spots appear on 
the leaves, but the cones escape ; while in other seasons infection 
is rapid and disastrous, extending from the leaves to the burr 
and cones. 
Prevention. — Hop bines from infected grounds should be burnt 
in order that all the asci upon them may be destroyed. Every 
particle of dead bines should be cut away in the early spring and 
burnt. Quicklime may be put over the hills in the winter. Sets 
or cuttings taken from plants that have been infected are very 
likely to spread infection. It is said that mould was introduced 
into Sussex with cuttings of new varieties. 
It would be well to dip suspected sets or cuttings in a solu- 
tion of sulphate of lime, or sulphate of copper; or lime and 
sulphur mixed should be dusted thickly over them. 
Weeds should be kept from hop grounds, especially the 
dandelion, Taraxacum dens leonis ; groundsel, Senecio vulgaris ; 
and other composite plants ; and plantain, Plantago ; which are 
hosts of the fungus. 
1 Mohl says the spores of the Erysiphere winter on the ground, as well as 
on the decayed leaves of their host plants. Ueler die Travlenkrankheit. 
Yon Hugo Mold, Botanisclie Zeituvy, Berlin, 1874, 
