Glasshouse thrips
On the territory of former Soviet Union this pest occurs everywhere in greenhouses, tropical houses and the conditions of outdoor planting. The glasshouse thrips injures more than 100 species of various ornamental, subtropical and tropical plants. In glass-covered ground it damages vegetable crops (cucumbers, tomatoes and others) and ornamental plants.
Biology. Life cycle
he female is black-brown, its length is 1.2–1.4 mm. The last 2–3rd segments of an abdomen are orange-yellow. The head is transversal, sometimes quadratic. The antennae are long, thin. The pre-thorax is transversal. The fore wings are developed, curved, transparent, dilated at the base. They have a furcular longitudinal vein. The tibiae (shanks) and the fore femurs are yellow. The abdominal segments at the sides have small protrusions.
The egg is 0.3 mm in length, transparent with a tender sheath. It is twisted. The female lays eggs in the epidermis of a leaf. The length of the 1st age larva is 0.5 mm. The larva is white. Its eyes are red. The length of the 2nd age larva is 1 mm. This larva is yellow its, eyes are also red. The larvae of both the ages have transparent walls of a body therefore the alimentary canal is visible. The length of a pronymph is about 1 mm. It is intensive-yellow with bright-red eyes and the primordia of the wings. Nymph length is about 1.3 mm. The nymph differs from the pronymph by the more developed primordia of the wings. Its antennae are directed backward and lie on a head in indusia (calypters).
Mode of life
The females and the eggs overwinter in the leaf epidermis of ornamental and evergreen trees. Under lowering of temperature to — 4–5°C of frost the thrips dies in all the stages of development (except eggs). In greenhouses it reproduces 3–4 generations per year. The females lay eggs in 3–6 days after wing formation. The female lays 2–3 eggs per day or on an average 22–25 eggs for her life. It forms a corky layer around the egg in leaf tissue, which protects developing organism from the influence of superfluous moisture. The pest lays eggs in young sappy leaves very seldom. Under the optimal conditions development lasts 28–30 days. At a temperature of about 40°C thermal stupor takes place. The lowest thermal threshold for development is 12–13°C. The optimum conditions for nymph and pronymph development are a relative air humidity of 70–85%, a temperature of 25–27°C. The insect is moisture-loving. Under the optimum temperature, but at a relative air humidity of 50% the high death rate of larvae, nymphs and pronymphs happens. The adult insects and the larvae prefer covered places, protected from direct sunlight.
Symptoms of injures
The pest pierces epidermis and sucks out cell sap. Settling on the undersides of leaves it causes their yellowing and silvering. The leaves wither and fall prematurely. The pale-yellow waxen spots emerge on fruits. The corky layer is formed on the surface of rind. Besides, the pest contaminates the fruits and the leaves with excrements.
