RED SPIDER

This pest is really wrongly named as it is neither entirely red nor a spider. There are several species, including the fruit tree red spider which is yellowish-green to reddish-purple and the glasshouse red spider. This pest is a mite, I.e. it has neither wings nor antennae, unlike a true insect. It differs from a spider proper in that it has 3 pairs of legs when young and 4 when adult (a spider has 4 throughout its life) and lacks clearly recognisable body segments.

These pests attack a wide range of plants, especially outdoors in very hot summers and in the greenhouse where they are encouraged by a dry , atmosphere and very hot pipes.

The mites are found in clusters on the undersides of the leaves, often near the veins. They suck the sap, causing mottling and yellowing of infested leaves, which fall to the ground prematurely, thereby weakening the plant. The glasshouse red spider attacks carnations, cucumbers, peaches, tomatoes and violets in frames. It overwinters in crevices of the brick or woodwork, in bamboo canes and similar places.

The fruit tree red spider damages apples, plums, pears, gooseberries and other fruits, the infested leaves turning a characteristic papery-brown colour.

Complete control of red spider mites is not easy. In the greenhouse, every effort should be made to avoid a dry heat and sudden temperature changes. Overcrowded plants are more likely to be attacked. Various insecticides are used to control these pests but the difficulty is to find a compound which is effective at all stages of the life cycle. Derris, lime-sulphur, azobenzene smoke generators, DNC, petroleum winter washes and malathion are some of the materials that have been used. Research continues to find the best answer to this problem and it is advisable to consult up-to-date literature of insecticide manufacturers to keep abreast with the latest developments as they affect the amateur.

REHMANNIA Although perennial this plant is usually treated as biennial. It is usually grown in a slightly heated greenhouse with a minimum winter temperature of 40—45 degrees F. Seeds are sown in June to bloom in early spring. Grow in John Innes Compost. The long spikes of Rehmannia angulata bear rose-pink, trumpet-shaped flowers resembling an incarvillea on plants 4 ft. tall. Can be increased by division in March when re-potting takes place.

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