12 September 1997

Integrated plan will keep slug risk to minimum

Waging war on slugs is a priority. But rather than routine use of pellets, growers should consider a more integrated approach. John Allan takes a look at current advice

SLUG control should revolve around a careful consideration of risk factors, together with field monitoring.

Such an approach ensures pellets are used only where needed – and used to best effect.

That is the view of Wolverhampton-based ADAS consultant David Green, whose guidelines for integrated slug control are outlined in the adjacent panel.

"Risk assessment tied to the weather forecast must be the basis of an integrated control strategy," he says.

Monitoring activity with bait traps is vital, since the population dynamics of slugs are not well understood. "Slugs are adept at coming through apparently adverse conditions well, so it is difficult to predict precisely how big a problem they might cause."

Peak activity can occur anytime between October and December and may drop even in apparently good conditions.

"Across an average field, 10 traps – not all on the headland -should give a good indication of slug activity."

He uses inverted 15cm (6in) plant pot saucers weighted down with a stone, taking care not to push the edges into the soil. That conceals the bait, ensuring wildlife is not exposed to slug pellets.

If four slugs are found per trap after three days a problem is possible. "But remember that a low or zero catch in dry conditions could underestimate the problem, so post-drilling monitoring is also important," he stresses.

Trapping before oilseed rape does not always work well, he adds. "Watch the crop very closely for leaf loss and slime trails, then immediately treat evidence of slug damage seen."

Elsewhere, control can be matched to need, in line with the adjacent strategy, he advises. Given the right conditions and a good formulation, there is a consistent 60-70% reduction of slug populations irrespective of the product used, Mr Green comments.