Early oilseed rape drillers are being advised to be proactive against slugs, as recent rains have heightened the risk of crop damage by the pest.

While this summer has delivered some warm and dry spells, much of the country has experienced regular showers and, in some regions, these have been heavy and thundery.

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Kent-based independent crop consultant James Rimmer of CCC Agronomy says his area of the South East has been particularly hard-hit by storms in late July and post-harvest stubbles are now the wettest he has seen for several seasons.

His clients either drill oilseed rape early during the first two weeks of August or wait until early September, trying to avoid peak adult cabbage stem flea beetle migration.

While the current abundance of moisture is ideal for rapid crop germination, Mr Rimmer says it also provides the ideal situation for slugs.

“We’ll be putting out traps to assess pressure before drilling, but I already get the feeling it could be a slug year this year because of soil conditions,” he adds.

Early treatment

Good seed-bed consolidation is key and where slugs are present – the treatment threshold for oilseed rape is just one slug per trap between sowing and the four true-leaf stage – he advises a slug pellet treatment at or very soon after drilling.

With establishment already difficult due to flea beetle, Mr Rimmer emphases the need to avoid additional problems that might hold seedlings back – including slugs grazing off cotyledons or true leaves as they emerge.

“I believe you need to apply a minimum of 50 baiting points/sq m early on. Last year I used mini ferric phosphate pellet Menorexx to achieve that.

“It’s also more cost effective because it gives you those 50 baiting points with a slightly lower dose than a standard-sized equivalent,” he explains.

Mr Rimmer adds that typical weather in early August means that even a mini pellet should give a reasonable duration of protection before reapplication.

However, if the weather deteriorates significantly while young oilseed rape crops are still susceptible to slug damage, he recommends switching to a standard sized pellet like Sluxx HP.