Forward planning – Slugs
With slugs being very visible in crops and stubble, there is an increased risk of slug damage to winter oilseed rape and winter cereals this season. Slug trapping can be used to assess the risk from slugs in a particular field. To get the best and most accurate results from slug trapping the bait placed under the trap needs to grab the slugs’ interest and to keep them there. The best bait is a dry food bait such as the breakfast cereal ‘Alpen’ or similar, or chicken feed (layers mash). Do not use slug pellets as bait. A tablespoon of the bait should be placed under the trap, which can be a slate, fertiliser bag, slug mat, an upturned flower-pot base, wooden board or something similar. Timing of trapping is crucial – place traps after there has been some rain (not a problem just now!), and the soil surface is moist. Traps should be checked in the morning before the day warms up too much, 1-2 days after being placed in the field. Consider using several traps per field so that you can determine whether some areas are more ‘sluggy’ than others, and trap regularly. If slug numbers exceed 5 per trap, especially if conditions have been suitable for slugs to be feeding on the soil surface (damp soil and humid nights) then the following winter wheat crop is likely to be at risk from slug damage. Only one slug per trap is enough to put winter oilseed rape at risk.
To reduce the risk of slug damage, aim to create a fine, firm seedbed for this autumns’ crop. Soil cultivation can reduce the risk of slug damage, as can deeper sowing of seed (3-4 cm).
With the loss of the neonicotinoid cereal seed treatments, protection from seed hollowing by slugs by this method is no longer available. Consequently, an application of slug pellets may be needed to protect the germinating seed as well as the shoots (up to GS12).
In oilseed rape, the germinating crop needs to be protected from slug damage up until the 4-leaf stage.
Generally, a pre-emergence application of pellets with a follow up post-emergence if damage is seen tends to do the job in both wheat and winter oilseed rape. However, further treatments may be necessary if the crop is slow to emerge or slug pressure is severe, which may well be the case this season.
Metaldehyde and ferric phosphate slug pellets will both do a decent job of preventing slug damage, but bear in mind the restrictions regarding metaldehyde use, particularly the 10 metre edge of the crop zone where metaldehyde pellets should not be applied. There are no restrictions for ferric phosphate pellets.
Note that all metaldehyde products have a use up date of 30th September 2021 or 31st December 2021 (depending on the product).
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