Slug and snail pests in Spanish crops and their economical importance.
In Spain as in many other countries there is very little information on the damage slugs and snails cause to vegetable crops and fruit trees. The species most frequently found in Spanish crops are Deroceras reticulatum, D. panormitanum, Milax gagates, Limax flavus, Arion ater, Theba pisana, Cepaea nemoralis and Helix aspersa. For control of these pests Spanish farmers apply 2500 tonnes of molluscicides/year, at a cost of 1000 millions pesetas - #5 million. To resolve this problem, a strategy is being developed to kill slug and snail eggs in the soil with light chemical compounds. The possibility of denaturing the outer layer of slug eggs with tannins from powdered bark of various trees (especially oak, holm oak, eucalyptus or chestnut trees) which have high quantities of tannin in their bark, will be explored in laboratory and field experiments.