Along with the multiple changes Brexit will bring to the agricultural industry, the recent ban announcement on the well-used molluscicide metaldehyde will be yet another blow. As of spring 2020, farmers in Britain will no longer be allowed to use the active product outside due to it ‘posing an unacceptable risk to birds and mammals’. The product will be phased out over the next 18 months, with it legally on sale for the next six months with the use of it for a further 12 months.
The benefits of metaldehyde are significant with slug control, where serious damage can be done to crops, particularly cereals and oil seed rape. The crop is most at threat from slugs when only recently sown, with up to around 50 seeds killed within the first week after sowing. However, they also attack the shoots and leaves, primarily of both wheat and rape, where leaf damage is often seen up to the four-true-leaf stage in rape. Heavy soils with high silt or clay content can increase the slug pressure, with crop residues also providing a good source of food and shelter.
In plot trials, metaldehyde seed treatments protected seedlings for up to 8 weeks after planting, having reached 6 true leaves therefore having the ability to outgrow any slug damage. However, in field trials, slug bait pellets were the only thing to protect the seedlings over the seed treatments. The seed treatments were seen on as a repellent and not fatal.
Cultural control measures can be taken to help reduce this risk, such as ploughing to bury trash and rolling after drilling to create a fine seedbed – these both will reduce the slug population as a fine seedbed makes it harder for them to move around and reduces the number of resting places. Metaldehyde Stewardship Group (MSG) suggest drilling at 3cm to deny access, and if drilling in cloddy seedbeds, increase the sowing depth to 4-5cm. An IPM (Integrated Pest Management) approach should be taken, more so now to help tackle the slug problem before the ban on Metaldehyde causes significant losses.
If you would like any further information, please contact Prue at email@example.com or your local FCG office.