Combatting the slug threat
Following optimum wet conditions, slug numbers are high and pose a particular threat to newly sown cereal crops, warn experts ...
Populations have increased significantly after a wet summer and for many, continued moist conditions throughout September, which is in stark contrast to the past two years which were both much drier and lower risk, says Hutchinsons’ Dick Neale.
“Continuous growth, breeding and egg laying, along with rapid volunteer growth and catch and cover crops, have all combined to generate a significant population in almost all situations, not just after winter oilseed rape.”
He explains that such high numbers make control more challenging and require vigilance from growers and agronomists, especially in the crucial early stages of establishment.
“At emergence, just a few minutes feeding on an individual seed or seedling can destroy the plant while post-emergence, the above ground leaves can tolerate far more grazing and still survive. Ultimately, we’ll never control slugs; the objective is to reduce the feeding population sufficiently to allow the newly sown crop to establish successfully,” says Dick.
With this in mind, he highlights five steps growers can take to help manage the risks from high slug populations this autumn:
Ensuring seedbeds are firm and well consolidated is the first step in reducing slug activity, as it makes it harder for the pest to move around and reduces the number of safe resting places compared with cloddy soils. “Doing so also improves seed-to-soil contact, which will help crops to establish faster and grow past the most susceptible stage for slug damage.”
With high numbers of slugs present in many fields, he says it’s vital to check newly-sown crops frequently – possibly daily – to look for signs of damage, assess slug activity, and decide on pelleting requirements.
“Remember, ferric phosphate pellets work completely differently to metaldehyde, as slugs feed and crawl off into the soil to die, so aren’t visible on the soil surface. This can make it harder to assess the effectiveness of pelleting strategies, other than through a reduction in crop damage, or the fact that all applied pellets have been eaten,” explains Dick.
He says that because slugs are generally random feeders, with higher populations it’s imperative that there are sufficient baiting points per m2 to increase the chances of slugs finding a pellet before the crop. “In wet years like this, slugs can number in the 100’s per m2, so a single application of 40-50, or even 90, pellets may not be enough,” he says.
“Equally, where pellets are being consumed quickly, repeat applications may be necessary to maintain sufficient baiting points throughout the crop’s most vulnerable stage. Label restrictions vary, but many products cannot be reapplied within one week, so if a repeat application is needed before that, then products will have to be alternated.”
According to Dick, the choice of slug pellet isn’t really an overriding issue when it comes to controlling such high numbers, although in continuously wet conditions and frequent rainfall, pasta-based pellets are more resilient than dry or steam processed pellets. “Recommended doses and the number of baiting points that dose will deliver do vary though, so consider options carefully. Some products also have limits on the number of applications that can be used, so always check the label carefully and consult your agronomist,” he concludes.
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