This section is from the book "Commercial Gardening Vol4", by John Weathers (the Editor). Also available from Amazon: Commercial Gardening, A Practical & Scientific Treatise For Market Gardeners.
The worst insect pests of the Cucumber are Thrips, Greenfly (aphides), Red Spider, slugs, woodlice, and Eelworm. Greenfly are easily kept in check by syringing the young plants occasionally with any of the soft soap, quassia, and nicotine washes on the market. Thrips and Red Spider will both soon appear if the atmosphere and soil are allowed to become too dry. Consequently the best natural remedies or preventives are the judicious application of water to the soil, pathways, and foliage, taking care that it is of the same temperature as that of the house itself. If these pests should get the upper hand, it will be necessary to fumigate or vaporize the houses to get rid of them.
Slugs and woodlice are sometimes troublesome, and will spoil the fruits if not suppressed. When cutting the fruits an eye may be kept on the slugs, everyone seen being dispatched on the spot. Traps of pieces of potato, beetroot, carrot, or mangel-wurzel may also be used for the slugs and woodlice, examining the pieces at intervals and destroying the pests in them.