Early oilseed rape drillers braced for slug pressure

Wet weather and chopped straw provide ‘ideal haven’ for slugs

The wet summer has provided good conditions for oilseed rape establishment – but growers who drilled early should prepare for high slug pressure.

That’s the message from independent agronomist Steve Cook who advises growers to put out slug traps at the time of drilling – and be primed to apply pellets if there is any evidence of slug activity.

For most situations, regular sized pellets should give good control levels. But where pressure is particularly high, an initial application of a mini ferric phosphate pellet product – such as Menorexx – could be beneficial.

High pressure

Smaller pellets provide a higher number of baiting points. But they are less durable in the wettest conditions, so growers should be prepared to follow up with another application shortly afterwards if required.

Seed rates also effect successful crop establishment. Anyone establishing crops in early August should use no more than 30 seeds/m2 for hybrids and 40-50 seeds/m2 for conventional varieties, says Mr Cook.

Independent crop consultant advisor Andrew Wells says he is expecting “scary” levels of slug pressure in early planted oilseed rape crops, especially where cereal straw was chopped rather than removed from the field.

But with large numbers of adult cabbage stem flea beetle seen in some harvested oilseed rape crops, Mr Wells thinks growers should be questioning whether it is worth the risk of planting the crop at all.

Accurate spread

Met Office figures show that the UK had 140.1mm of rain in July – the sixth highest total since records began in 1836. A succession of low pressure systems saw long periods of damp and windy weather.

For those who did drill early, getting on top of slugs as soon as the crop is established iscrucial.  Alongside trapping to gauge pressure, it could be worth going further and looking for signs of grazing on cereal volunteers before the crop is established.

If it looks like there is significant activity, growers should apply pellets as soon as the crop is in the ground, says Mr Wells.

Accurate application is essential, which means using a good quality, durable pellet, such as Sluxx HP, and an applicator capable of spreading evenly to the chosen spreading width.

“Every year I see gaps in the crop that are caused by inaccurate spreading, so it’s important to make sure that applicators are actually spreading pellets to the desired distance, rather than just going off the settings in the book,” says Mr Wells.