. California greenhouse pests and their control. Insect pests; Greenhouse plants. APHIDS Importance: Aphids, or plant-lice, are well-known insects that infest nearly all types of plants. They are commonly found in colonies on the shoots of new growth, but they also occur under leaves, on stems, or on bulbs and roots. They injure the plants by sucking the juices with a long beak, and the new leaves are curled and crinkled by their feeding. They also excrete a honeydew which may be produced in such quantities as to form a glistening coating on the leaves and branches. This honeydew attracts ants
. California greenhouse pests and their control. Insect pests; Greenhouse plants. APHIDS Importance: Aphids, or plant-lice, are well-known insects that infest nearly all types of plants. They are commonly found in colonies on the shoots of new growth, but they also occur under leaves, on stems, or on bulbs and roots. They injure the plants by sucking the juices with a long beak, and the new leaves are curled and crinkled by their feeding. They also excrete a honeydew which may be produced in such quantities as to form a glistening coating on the leaves and branches. This honeydew attracts ants and promotes the growth of the black smut fungus. Aphids also serve as the agents for transmission of a large number of plant virus diseases. The green peach aphid is known to transmit carnation streak, lily mottle virus, pansy and viola flower breaking, gladiolus mosaic, stock mosaic, ornithogalum mosaic, as well as mosaics in tritonia, babiana, ixia, sparaxis, strep- tanthera, and watsonia. The potato aphid, the cotton or melon aphid, the bean or dock aphid, the lily aphid, and the fox- glove aphid also transmit certain of these viruses. Several other plant virus diseases such as narcissus mosaic, narcissus white streak, tigridia mosaic, and Easter lily necrotic fleck, are transmitted by certain of the latter aphids. Appearance: Aphids are soft-bodied, usually with long legs and antennae, and ordinarily possessing a pair of tubes near the end of the body which are called cor- nicles. Adults are generally from 1/12 to 1/8 inch in length, and they are colored greenish, yellowish, pink, purplish, brown or black. Most species have winged as well as wingless forms. Development: The life cycle of aphids is often complicated, and various species may differ considerably in details of de- velopment. Most of the aphids found in greenhouses, however, omit the egg stage entirely, and reproduction is continuous Fig. 15. Effect of stock mosaic, a virus disease transmitted by cer- tain aph
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