Slugs may take toll on late drillings

Take care not to let slugs slip into late sown cereals, growers are being urged.

Although the pests hit many of this season’s oilseed rape sowings, damage to winter wheat and barley drillings so far has generally been no worse than usual, thanks to some excellent seed-beds and rapid crop emergence.

But nationwide trapping (see shows that even after the long dry spell, there are still plenty of slugs waiting to feast on newly sown seeds lying in cooler, moister and often cloddier seed-beds, specialists warn.

“Certainly there are above [treatment] threshold numbers in the fields I have been monitoring in Somerset,” says Styloma’s David Glen.

Recent counts on one wheat stubble (see table) have shot up since mid-September.

“The numbers are about as high as anything I have recorded anywhere.”

In the east of the country, levels appear lower, but there have been few weather windows suitable for trapping, notes ADAS’s Greg Talbot.

“We had quite a bit of damage to oilseed rape earlier on.”

“Certainly our August and early September trapping on oilseed rape stubbles going into wheat showed levels at or above threshold in the West Midlands,” says colleague David Green.

“The concern is that slug populations are still high,” says Suffolk-based consultant Colin Myram.

“Up to now, conditions have been ideal for getting well consolidated seed-beds, crops have come through quickly and there has only been a bit of grazing.”

The danger is that later sowings into wetter soils that are cooling down and cannot be rolled because of poor conditions are much more at risk, he adds.

“Grain hollowing could be a serious problem.”

Although earlier sowings largely escaped slug predation, prolonged dry weather has recently made it harder to achieve good seed-beds, notes Frontier’s Beds-based Bob Mills.

“They’ve been a bit more cobbly.

What has been drilled in the past week or so and will be from now on could be more affected, especially with rain coming.”

Velcourt’s Keith Norman says: “The weather has been on our side, but several of our managers are telling me they have never seen so many slugs.”

Rain will soon flush out lurking slug populations, warns the SAC’s Andy Evans.

“Growers with any wheat left to go in need to be careful they don’t get caught out.”

Ideally, growers should use the HGCA’s Topic Sheet Decision Trees (Arable, 2 Sept) and continue to trap before cultivating for sowing, provided conditions are suitable, advises Prof Glen.

“They should then be prepared to apply pellets as soon as possible after drilling if they find four or more slugs per trap.”

But not all growers, under pressure to get crops sown, will be able to trap in order to justify treatments, says Mr Myram.

“If they don’t have the time, I’d suggest going on with relatively inexpensive pellets based on metaldehyde, which is safer to the environment.”

For Velcourt’s managers, previous cropping, seed-bed quality, drilling depth and careful monitoring are just as important guides as trapping, says Mr Norman.

“We can’t afford routine applications, but trapping is only indicative [of problems] – it’s not black and white.”