. California greenhouse pests and their control. Insect pests; Greenhouse plants. insecticides are more satisfactory, how- ever. They are applied to the surface of the soil, either as sprays or dusts. 1. DDT. (See page 52.) 2. Chlordane. (See page 51.) 3. Benzene hexachloride. (See page 50.) 4. Parathion. (See page 57.) NEMATODES Importance: Nematodes which infest plants are very destructive. They injure the plants by killing tissues or by produc- ing abnormal growth. Several species are found occasionally in California green- houses. Appearance: Nematodes are round worms, without body segment
. California greenhouse pests and their control. Insect pests; Greenhouse plants. insecticides are more satisfactory, how- ever. They are applied to the surface of the soil, either as sprays or dusts. 1. DDT. (See page 52.) 2. Chlordane. (See page 51.) 3. Benzene hexachloride. (See page 50.) 4. Parathion. (See page 57.) NEMATODES Importance: Nematodes which infest plants are very destructive. They injure the plants by killing tissues or by produc- ing abnormal growth. Several species are found occasionally in California green- houses. Appearance: Nematodes are round worms, without body segments. The ones which infest plants are very small, mature females being about 1/20 inch long. Ex- ceedingly large numbers may be present. It is by their characteristic injury that the presence of nematodes is suspected. Development: Eggs are laid where they feed, and the worms mature in from two to four weeks. Adult females may each lay several hundred eggs. Species Found In California Greenhouses Root-knot nematode, Heterodera marioni (Cornu), works in the roots, causing gall forma- tions which interfere with the transportation system of the plant. Infested plants become stunted, sickly, and often die. Young larvae which wander through the soil are responsible for new attacks. A very wide variety of green- house plants are subject to infestation. Foliar nematode, Aphelenchoides olesistus (Ritzema Bos), works in fleshy leaf tissues, pro- ducing irregular, blackened patches. Adults are able to wander over the surface of the plant in films of moisture, and they are capable of re- maining dormant for some time. A number of greenhouse plants are subject to infestation, common ones being African violet and pepero- mia. Birds-nest fern is often infested by a simi- lar form. Bulb and stem nematode, Ditylenchus dipsacl (Kiihn), works in bulbs, stems, or leaves, pro- ducing swellings, twisting, and stunted growth. The mature larvae may wander through the soil to infest new plants, and this
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