Control of slug and snail damage

Abstract

This study has shown that slug feeding can be manipulated using a range of secondary metabolites found in plant tissues. Chemicals have been identified which reduce or prevent slug feeding when incorporated into wheat flour pellets or when sprayed onto plant leaves.

In a systematic study of the family Apiaceae (Umbelliferae) species representing thirty-two of the forty-two genera found in the UK yielded extracts which influenced slug feeding behaviour. Eleven antifeedant chemicals were identified including alcohols, aldehydes and alkaloids suggesting that slug feeing may be controlled by chemicals which have different physiological and toxicological characteristics, some of which may be suitable for practical application as plant protectants.

When the most active slug feeding deterrent, the alkaloid identified from hemlock, was sprayed onto young Chinese cabbage plants exposed to large numbers of starved slugs the plants remained undamaged over the 24-hour test period.

The most serious damage to cereals caused by slugs is done to the newly-sown seed when the embryo is eaten and germination prevented. A seed treatment which deterred slug feeding until the plant started active growth would largely solve the problem. In this initial investigation eleven chemicals with slug antifeedant activity were identified in a survey of only thirty-three plant species. Any one of these may have the correct combination of antifeedant activity, phytotoxicity and persistence for successful deployment as a seed dressing and there must be very many more waiting to be found.

Development of a successful antifeedant cereal seed dressing would largely obviate the need to use conventional molluscicide pellets, with consequent savings in cost and a reduction in pesticide usage on the crop.