This section is from the book "Commercial Gardening Vol3", by John Weathers (the Editor). Also available from Amazon: Commercial Gardening, A Practical & Scientific Treatise For Market Gardeners.
The Red Spider of the Gooseberry is frequently very harmful. It is distinct from others we find on Ivy, and Apple, and Peach. This acarid attacks the buds and young leaves, stunts their growth, and produces a curious dull mottling of the leaves.
Fig. 373. - Gooseberry and Currant Sawfly (Nematus ribesii).
1, Shoot of gooseberry. 2, Eggs. 3, Larva. 4, Pupa. 5, Perfect insect.
The Gooseberry Red Spider belongs to the genus Bryobia, which differs from Tetranychus, the Red Spider of the Vine, etc, in that its first pair of legs are longer than the other three pairs. The mites of this genus spin no webbing of silk. The damage is done by the mites constantly sucking the sap from the leaves. In colour this acarus is very variable. Some are grey, others greenish, others rusty red, others leaden grey or bright red; the legs are pale or dull reddish. In size the mature specimen may reach about ^V in. During dull weather, in early spring, they collect in crevices on the wood and under the rind upon it. In this manner they may be seen in February, and usually of a rich red colour. When it becomes warm and sunny the acari crawl about and feed on the buds and young leaves. Later, when the leaves are older, they are found mainly on the under side of them. As soon as it becomes dull, or turns cold, they take shelter at once, and also return to shelter at night, In late March, but usually in April, they start laying shiny red globular eggs on the wood, bases of thorns, and between old bud scales.
These eggs hatch in four or five days into small six-legged transparent acari - the larval Red Spiders. After moulting three times, they are ready to breed again at the end of fourteen days. The winter seems to be passed in both the egg and immature condition.
The old remedy for Red Spider was liver of sulphur, at the rate of 3 to 5 oz. to 10 gall, of water. Now paraffin jelly is found to be much more effectual. This is made by boiling 5 gall, of paraffin and 8 lb. of soft soap together, and whilst boiling add 1 pt. of cold water and then well stir. This becomes a jelly on cooling, and can be used at the rate of 10 lb. to every 40 gall, of water.