Growers should not worry about the loss of metaldehyde from the slug control product armoury, says Herefordshire-based Hutchinsons agronomist Andrew Goodinson, as good quality ferric phosphate alternatives are as every bit as effective in trials and provide a better environmental footprint.
Mr Goodinson highlights that ferric phosphate is a good insurance against OSR crop loss caused by poor establishment – ultimately it is about protecting plants that have been drilled into poor seedbed conditions and are at high risk from slug grazing, including crops that are showing flea-beetle damage.
“Last autumn we would still have had a challenge to establish OSR crops, even without the flea beetle issue, because of the dry, cloddy seedbeds. Seedbed conditions are more important than drilling date. If conditions aren't right for planting OSR, then don't," he says.
“Flea beetle exacerbated the problem last year, so growers must look at all cultural and treatment options for helping crops to establish. Ferric phosphate will have a significant role to play in slug control going forward."
Mr Goodinson has been using ferric phosphate for over five years, during which time he phased out metaldehyde in his search for safer alternatives with a better environmental profile.
“Metaldehyde has always been a cost-effective slug control option where applied properly," he adds.
“Ferric phosphate has proven to be a perfect replacement, matching metaldehyde for efficacy and cost effectiveness.”
Mr Goodinson was surprised when he learned at a meeting about water quality in Hereford last year that around 75% of growers were still using metaldehyde.
He pointed to a number of studies undertaken by Hutchinsons' foundation agronomists, which found that while the level of control was the same, slugs' habits having ingested either product was very different.
In the case of ferric phosphate-treated slugs, they stopped eating immediately and retreated underground where they died within a few days.
“Whilst the lack of physical evidence seemingly put some growers off ferric phosphate, the fact is that metaldehyde-treated slugs die on the surface and are more visible,” says Mr Goodinson.
“We have found that crops recover more quickly where ferric phosphate has been applied, which is probably to do with the fact that the slugs in crops treated with metaldehyde continue to feed for some time having ingested the product before dying. Application timing is also critical with adult slugs being the target rather than the juveniles, especially in cereals. Therefore, regular monitoring of traps is essential.”
In terms of pellet quality he recommends wet process ferric pellets, which spread well, giving even coverage and baiting points.
“Bait quality is critical to the level of control, so always consider ballistics, pellet persistency, uniformity and palatability. Poor quality pellets cannot be applied accurately over wide distances (max 15m) so the weight and shape of each pellet has to be consistent, to ensure even application and accuracy is maintained across the full working width," Mr Goodinson says.
Applying slug pellets accurately is difficult when broadcast, he says. It is less precise and there is inevitably more overlap. Therefore the quality of application machinery is also critical to ensure accuracy.
“Operators will have already been following strict regulatory standards and demonstrated due diligence when applying metaldehyde, so these skills can simply be carried across to a ferric phosphate-based application, but without the same environmental concerns,” he adds.