Oilseed crops
Already some winter oilseed rape crops have had to be re-drilled in the West Country this autumn due to significant slug damage.
The likelihood of continuing pest pressure in winter crops, plus the need to preserve water quality, will necessitate a planned approach to controlling slugs using a number of different active ingredients within the programme.
Dr David Stormonth, technical manager for specialists Interfarm, said following the wettest summer for 100 years, slug pressure had been immense – which could only mean a significantly higher threat than usual this autumn.
He said: "While cultural control should be the first option, by creating firm, fine seedbeds to limit slug activity, growers should then consider using suitable slug pellets, when trapping indicates thresholds have been exceeded. In wheat thresholds are four slugs per trap, but in rape only one slug per trap."
Controlling slugs has become more complex because of the need to commit to stewardship guidelines for the application of metaldehyde-based slug pellets in order to avoid risk of water contamination.
No more than a total of 210gms of metaldehyde per hectare can be applied between August and the end of December.
"There is also a further maximum of 700gms for each calendar year.
With these restrictions on the use of metaldehyde, this autumn many growers will require another active ingredient, such as methiocarb, within their slug control programmes," said Dr Stormonth.
He suggested that growers introduced Cobra into their programmes.
"Containing four per cent methiocarb, Cobra is a modern high-quality wet, extruded pellet, which maintains its integrity, even in wet conditions," he added.
"Not only is it very durable, giving long-lasting persistence with the possibility of fewer applications, but it has good ballistic properties for an even application on the soil surface.
Cobra is a stomach poison which means the slugs rarely recover and it continues to work effectively even when it is cold and wet."
He said methiocarb was more than eight times less soluble than metaldehyde and that it bound tightly to the soil.
"This means lower risk of contaminating surface water. Metaldehyde slug pellets must not be applied within six metres of a waterway, so methiocarb can be used in these circumstances."
He advised growers to monitor winter cereals from sowing to the start of tillering, and OSR from sowing to four true leaves.
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Source: thisisdevon