The mollusc menace

Arnold du Preez, owner of Snail and Slug Solutions, warns that the surge in slug and snail populations will prove a major threat to agriculture unless farmers tackle the problem proactively. He spoke to Glenneis Kriel.

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You’ve said that slug and snail numbers have shot up in recent years, leading to ever-greater damage to crops. Do you know what has caused this problem?

We’ve seen an explosion in snail and slug populations on farms over the past decade or so, resulting in commensurate damage to vegetables, fruit and grain.

Various factors have contributed to the problem. For one, the overuse of pesticides and other chemical products has destroyed the biological equilibrium on many farms. As a result, fewer natural predators, such as snakes and frogs, are available to keep slug and snail populations in check.

There are also fewer microbes in the soil to feed on slug and snail eggs.

Paradoxically, the switch to minimum- and no-tillage farming has exacerbated the problem, as these practices don’t destroy the slug and snail populations in the way that ploughing does. In addition, cover crops and mulches help to create a favourably cool habitat for them.

Many people think that using wood chips or other coarse mulch can help to deter slugs and snails, but they can slide over a razor blade, so these materials do them no harm.

On top of this, weather patterns are changing. In the Western Cape, for example, rainy days interspersed among the normal hot summer days over the past few years have produced favourable breeding conditions for molluscs.

All of these factors mean that slugs and snails have been able to lay huge numbers of eggs, and without interference.

Do molluscs have any inherent breeding advantages?