. California greenhouse pests and their control. Insect pests; Greenhouse plants. Appearance: The larvae are small, fleshy maggots, without a head, and often yellowish or orange in color. They are commonly about 1/12 inch in length. The adults are very delicate midges, usually reddish in color, and less than 1/12 inch in length. Development: Eggs of gall-making species are laid on the new growth. The galls develop around the maggots as they feed. The transformation stage is usually found in the gall. The adult midges live only a day or so. The period from egg to adult is about one month in the
. California greenhouse pests and their control. Insect pests; Greenhouse plants. Appearance: The larvae are small, fleshy maggots, without a head, and often yellowish or orange in color. They are commonly about 1/12 inch in length. The adults are very delicate midges, usually reddish in color, and less than 1/12 inch in length. Development: Eggs of gall-making species are laid on the new growth. The galls develop around the maggots as they feed. The transformation stage is usually found in the gall. The adult midges live only a day or so. The period from egg to adult is about one month in the case of the chrysanthemum gall midge, and the adult female may lay as many as 100 eggs. Important Greenhouse Species Chrysanthemum gall midge, Diarthron- omyia chrysanthemi Ahlberg. Individual cone-shaped galls are formed on the leaves and stems. These may be so abun- dant that the leaves are deformed and the stems gnarled and misshapen. Only chrysanthemums are attacked, although some varieties are more susceptible to injury than others. It is a common green- house pest, although outside infestations also occur along the coast. CONTROL Until recently the chrysanthemum gall midge has been very difficult to con- trol. Certain of the newer insecticides, however, are very effective. 1. DDT: adult control. (See page 52.) 2. Benzene hexachloride: excellent con- trol of adults and immature stages within the galls. (See page 50.) BULB FLIES Importance: The maggots of several species of bulb flies are found commonly in association with bulbs of all types. One of these species is of considerable im- portance in destroying bulbs. Certain others may be secondary, the maggots preferring to feed on diseased or infested rootstocks. Bulb flies are primarily pests under field conditions, but infested bulbs are transferred to greenhouses. Appearance: Bulb fly maggots are fleshy, whitish or dirty gray, without legs or a head but with a short, brown tube at the back end. They are from 1/2 to 3/4
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