. Destructive insects. Insect pests. — 19 — face and to the branches. Here the winged form develops, and then makes its way to new quarters, founding new colonies wherever it reaches, and these about midsummer make their way to the ground and to the roots. Usually some few specimens are to be found on the leaves throughout the summer, but they are much more abundant in spring. No males of this species have been observed, and no eggs have been found. Plum Aphis. Aphis prunifolia, Fig. 25. This is a species of plant lice attacking the young shoots and under- side of plum and prune leaves
. Destructive insects. Insect pests. — 19 — face and to the branches. Here the winged form develops, and then makes its way to new quarters, founding new colonies wherever it reaches, and these about midsummer make their way to the ground and to the roots. Usually some few specimens are to be found on the leaves throughout the summer, but they are much more abundant in spring. No males of this species have been observed, and no eggs have been found. Plum Aphis. Aphis prunifolia, Fig. 25. This is a species of plant lice attacking the young shoots and under- side of plum and prune leaves, puncturing them and sucking the sap, thereby checking the growth of the tree and the development of the fruit. When first hatched they are of a whitish color tinged with green, but as they increase in size they become a deeper green, and when mature some of them are dark with pale green abdomens and dusky wings; eyes dark brown. The insect and infested leaves are covered with a whitish powder. This aphis has proved exceedingly destructive in several prune- growing districts. Upon the first appearance of the lice the trees should be immediately sprayed with the rosin wash recommended for young black scale, care being taken to wet the underside of the leaves. Like all other aphis they increase enormously, and a second spraying may be necessary later on. The Hop Aphis. Phorodon humuli. Considerable alarm was occasioned in May last, amongst the hop raisers of the State, by a report that the'hop louse had made its appear- ance in several fields in the neighborhood of Sacramento. Numerous letters and boxes containing apliis were received at this office, but none contained the true Phorodon humuli. The first box contained leaves- of wild radish infested with cabbage lice (Aphis hrassicx); these were found in a hop yard. Other boxes contained the plum louse (Aphis pricnifolia), but the only insects found upon hop vines received w^ere the grain aphis (Siphonophora avenm). These la
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectinsectpests, bookyear
