Don’t be fooled into thinking the hot June and July has diminished the threat from slugs for the coming season, particularly with wet weather returning in August.

Bayer CropScience’s Slugwatch showed high levels of slug activity during the wettest May on record for many areas.

But activity dropped during the two subsequent hot, dry months, when average numbers of slugs at the 20 sites monitored fell from 54/sq m in May to 15/sq m.

Despite that the firm’s Richard Meredith believes good over-wintering and ideal conditions in May has set them up for the summer.

“The number of juveniles evident in the spring certainly shows there was plenty of potential for population growth at that point, and conditions in August will be critical to kick-starting activity again, particularly in relation to early-drilled crops.”

Treatments

With slugs likely to have “gone to ground” in July’s hot temperatures, cereal seed treatments, such as the Secur (imidacloprid)/Deter (clothianidin) ranges, could prove effective this season, he suggests.

“We found after the hot, dry summer of 2003 they were particularly beneficial, as slugs migrating from depth encountered the seed before the slug pellets.

The combination of seed treatment and pellet application was shown by trials in that year to be an excellent belt and braces approach.”

Dr Meredith urges growers to keep an eye on the weather.

“When there is a wet spell carry out some surface monitoring to check for activity.

Treatment threshold is four slugs per trap for cereals, less for oilseed rape and just one in cereal stubble prior to drilling rape.”

Monitoring traps should be an upturned dish, about 25cm in diameter, baited with a couple of teaspoons of chicken feed underneath, he says.

“They should be revisited early the next morning before the sun heats them up.”

It is also important for growers to establish what slug species they are up against, he says.

“They can then select the most effective active ingredient, particularly when a range of species is present.”

mike.abram@rbi.co.uk