Advancements in chemistry are providing growers with flexibility when managing slug pressures in potato crops.
Flexibility in slug control
The mild and wet weather and lack of ground frosts seen this winter, means that being vigilant to slug activity will be key as we move into the potato planting season.
Andrew Sprunt, Agrii’s Northern region potato technical agronomist, explains what growers can expect from the season ahead, and how to manage the potential impact at farm level, particularly in light of the demise of methiocarb.
“This winter has allowed a longer breeding season for slugs. We’ve seen temperatures remain above average throughout the autumn and early winter. And, in many parts of the country, over the last three to four months, we’ve also had up to two thirds of the average annual rainfall.
“Therefore, there is a heightened risk from slug populations going into this season, particularly from juvenile slugs,” says Mr Sprunt.
Managing the impact
If not controlled, slug damage has the ability to cost the agricultural industry up to £100 million per year. “Not only this, we have to remember that one slug has the ability to reproduce over four million offspring in a single year, and it’s juvenile slugs that are particularly active feeders, causing a high level of damage,” says Mr Sprunt.
“Within potato crops, a very low pest and disease threshold is tolerated, only 3% in packed potatoes, and the threat from crop rejection is a big consideration considering the high value nature of this sector.
“Therefore, as we move into the spring, and conditions look set to stay relatively wet, particularly in the north, a proactive approach to slug control will be key,” he adds.
Mr Sprunt explains that slug control should be a factor considered before potatoes have even gone in the ground. Growers should be assessing the risk in fields in advance of planting, with the objective of helping reduce slug populations for the later part of the season, when damage can have the greatest impact financially.
“Soil type, variety choice, field history and location, and awareness of the risk presented by previous crops are all factors that should be taken into account when devising a slug control strategy suited to the season ahead,” he says.
“Maris Piper is still the variety of choice for UK growers, but it remains one of the most susceptible varieties to slug damage. But, for those growing this variety, or other susceptible varieties, there are ways that the risk can be managed.
“Firstly, consider the soil type. Slugs generally prefer heavier soils such as clays and sandy clay loam soils, due to their ability to move up and down the soil profile with ease. So refraining, were possible, from planting susceptible varieties on these soils will help. Soil conditions may also change throughout the season, so adjusting the strategy to take this into account is advised.”
Whether renting or using purchased land to grow potatoes, it’s also key to look at the rotation and, in particular the previous crop before planting. “Avoiding planting potatoes in close proximity to oilseed rape in particular, and knowing the historical slug pressures in certain fields, will help map out lower risk areas most suited to growing potatoes.
“Cropping history is a valuable resource that should be used to help minimise the risk of slug damage. Where oilseed rape has been grown close in the rotation, or if slug populations have been historically high, an application of slug pellets pre-planting may be beneficial,” he adds.
Slug pellet chemistry advancements
Once potential risk factors have been identified, Mr Sprunt explains the importance of pellet choice to suit the system and the proposed strategy.
“The loss of methiocarb has meant that growers have had to seek alternative molluscicides, namely metaldehyde and ferric phosphate. But, we’ve also seen advancements in the formulation of pellets which is providing growers with a greater degree of flexibility when choosing and applying pellets.”
Longevity, spreadability and efficacy are key characteristics that are paramount for the formulation of slug pellets. “Many pellets now on the market are pasta based and wet processed, rather than dry processed. This means that in wet conditions particularly, the pellets are more cohesive and tend to maintain their integrity for a longer length of time.
“The ability to broadcast pellets to wider widths, evenly and without breakages, is also becoming more important due to the increasing popularity for GPS systems and the trend towards operating 36 metre tram line systems. Modern pellets are therefore evolving to meet this demand,” says Mr Sprunt.
A recent trial carried out by Spreader and Sprayer Testing Ltd (SCS) has evaluated Certis’ advanced formulation ferric phosphate slug pellet, Sluxx HP, and its spreading characteristics in comparison to other pellets on the market.
Results have shown that 99% of Sluxx HP pellets were between 2mm and 3.3mm, more consistent than other pellets trialled, and weighed in at 0.77kg/l, also denser than the other pellets. These results are significant for growers and demonstrates how companies are developing crop protection products to suit modern farming systems and machinery.
“The loss of methiocarb has had an impact on the potato industry especially. But, we need to make sure that we continue to use the remaining actives in a responsible way.
“Looking at how metaldehyde and ferric phosphate can be used in a synergistic way, as part of a complete slug control strategy, will help ensure crops meet their saleable potential and don’t exceed pest and disease tolerance levels,” says Mr Sprunt.
Advanced formulation – Sluxx HP
Ensuring their potato portfolio continues to advance and meets the demands of the industry, has been a key driver in the formulation advancements of Certis’ ferric phosphate slug pellet Sluxx to Sluxx HP.
Morley Benson, Certis’ key account manager, explains how listening to grower and agronomist feedback has led to the further development of an established and strong performing pellet that fits well within an integrated crop management strategy.
“When we initially launched Sluxx there was some concern that the pellet colour was not easily visible in the field. As a result, we’ve built on the success of this ferric phosphate based pellet by making it a more vibrant, deep blue colour that, even after heavy rainfall, remains highly visible in the field.
“Alongside this, we also took the opportunity to further enhance the persistency of the pellet in wet weather, with the addition of mould inhibitors to the formulation. The changes from Sluxx to Sluxx HP has already gone down well with growers,” he says.
Mr Benson explains that Sluxx HP has also retained its strong environmental profile, having no impact on non-target organisms, no buffer zone restrictions and a zero harvest interval.
“Ferric phosphate offers growers the flexibility in situations where there may be restrictions on the use of metaldehyde.
“For example, if growers have already exceeded the statutory 700g of metaldehyde active substance per hectare per year during the autumn, then ferric phosphate is the only option for spring applications. It offers the environmental credentials to ensure the potential risks to water are reduced, and harvest interval is not an issue,” he says.
“There is room for both active ingredients in the market place. And if used effectively in an integrated programme alongside cultural controls, both actives can continue to offer a good level of slug control, which will be key this season, considering the potential high, upcoming slug pressures in potato crops,” says Mr Benson.