9 August 2002

Strike at slug pest right after harvest

By Andrew Blake

HIT slugs straight after harvest to help guard autumn sowings against the damaging pest, advises an SAC specialist.

"This seasons wet weather has been so conducive to slugs that populations have reached one of the highest in 10 years," says Andy Evans. "We have received numerous reports of slugs crawling up stems and feeding off maturing cereals."

The post-combining targeted approach offers effective long-term control and is already successfully practiced by French growers, notes Dr Evans. "The key is to knock the slugs before they have a chance to mate and lay eggs."

Growers who suspect they may have a slug problem should consider applying mini metaldehyde pellets as soon as trap thresholds are reached and before seasonal cultivations begin, he stresses.

Broadcasting onto moist soil in the south in mid-August should knock back populations and reduce numbers in subsequent seasons. For growers further north the end of the month will be more appropriate.

Traps should be introduced before harvest, using either a robust plastic bag or hardboard, with a suitable bait, he advises. If the threshold of five slugs a trap is reached a day after ideal conditions for them to be active on the soil surface, action should be taken.

One week later, traps should be reintroduced to gauge how effective the first application was. If necessary more treatments should be made.

Mini pellets are cost-effective because they offer plenty of chances for the pests to find them, he explains. "They should be broadcast after the soil surface has been moistened, either through rainfall or irrigation, to ensure a greater likelihood of slug contact."

In France, trials have confirmed that metaldehyde used in wet conditions, five to 10 days before drilling, helps cut populations waiting to attack germinating crops, says Jean Francois Testut of CDP Clartex.

"Broadcasting quality wet processed metaldehyde slug pellets at the time of drilling remains essential for French growers," he says.

"However, we have found that an additional application in the run-up to drilling is cost-effective providing the weather is favourable for slug activity and the soil is sufficiently bare for them to find the pellets."

The tactics are particularly useful after oilseed rape, notes Mr Testut.

Despite some misconception metaldehyde gives consistent results in both wet and dry conditions and its mode of action is not affected by rain or damp weather, notes Malcolm Nursey of pellet supplier Luxan.

The firms new product, Deal, a 6% metaldehyde-based molluscicide is made from durum wheat. This makes it highly palatable and ensures the pests consume a lethal dose, he explains. It includes Bitrex mammal deterrent.

Deals wet-process manufacture helps it resist weathering and breakdown in wet conditions, and its uniform size aids spreading, he adds. At 8kg/ha it provides 52 bait points/sq m. Cost is £2.60/kg.

"With the weather so unpredictable in the UK, farmers need a pellet that provides effective protection in both wet and dry conditions." &#42

SLUG TREATMENT

&#8226 Wet weather = high populations.

&#8226 Pre-cultivation baiting advised.

&#8226 Aim to kill before breeding.

&#8226 Long-term control target.