22 THE HOP APHIS IK THE PACIFIC REGION. 
severely injured that they were not worth picking, and they were left 
in the field. (See PI'. IV, figs. 1,2.) 
Where control work is attempted the infestation seldom becomes so 
severe as to retard the growth of the vines, and it is the late injury — 
the accumulation of honeydew upon the cones and the resulting 
growth of the black fungus — which is most to be feared. 
HONEYDEW AND ITS EFFECT ON THE HOPS. 
Honeydew is a substance which is excreted from the anal opening 
of the aphides. It is composed largely of gums and sugar and is 
sticky and sweet to the taste. On warm afternoons it may be seen 
falling as a mist from severely infested vines. 
Hops covered with honeydew are sticky, do not have the normal 
amount of crispness, and when pressed between the fingers remain 
flattened out. Honeydew may under some circumstances increase 
the weight of the crop. One grower estimated that he made $1,000 
on honeydew in 1911. However, the quality of the crop was greatly 
injured, and had the demand for hops been less the grower would not 
have been able to sell, and his crop would have been a complete loss. 
Even though under certain uncontrollable circumstances the pres- 
ence of honeydew may increase the income from a crop of hops, their 
quality is injured, and the hone} T dew is the medium for the black-smut 
fungus, which will, in ninety-nine cases out of one hundred, so injure 
the quality of the crop that it will be unsalable. 
BLACKENING OF HOPS. 
Neither the honeydew nor the aphides are directly responsible for 
the blackening of the hops. The blackening is due to a smut fungus 
(Cladosporium sp.) commonly called "mold," which grows upon the 
honeydew. If the honeydew happens to be upon the hop cones, this 
fungus gives the hops a black, moldy appearance, which is extremely 
undesirable. 
NATURAL ENEMIES. 
Several predaceous insects have been observed attacking the hop 
aphis at Perkins and at Santa Rosa, Cal. The ladybirds Hippodamia 
convergens Guer., Coccinella californicaMeamh., Coccinella abdominalis 
Say, and Chilocorus orbus Cas. were frequently found among the 
aphides. Some eggs of Hippodamia convergens deposited among the 
hop aphides are shown in Plate V, figure 1. Chrysopa calif omica 
Coq. was always abundant in the hop fields, and the larvae were 
very active in feeding upon the aphides. 
The larva? of syrphus flies (PI. V, fig. 2) were abundant in the 
hopyards. Syrphus opinator O. S. and Syrphus ameiicanus Wied. 
were reared from the larva? which were collected from hop leaves. 
