Open day provides insight into potential potato solutions – Farmers Guide
From loss of actives to emerging pests, the UK potato sector faces numerous challenges ...
From loss of actives to emerging pests, the UK potato sector faces numerous challenges. Visitors to the Hutchinsons Potato Demonstration Day, held at Worth Farms, Holbeach, Lincolnshire recently, gained an insight into some of the potential solutions the agronomy firm is exploring.
With uncertainty surrounding the future of some key potato actives, the trials heavily focused on alternative means of control.
This included for the pre-emergence herbicide, metribuzin which has played an important role in potato weed control for decades. Having just been withdrawn in Europe, UK growers face the same potential fate, warned Darryl Shailes, Hutchinsons root crop technical manager.
“The herbicide is registered here until 2030, so that gives us around five years to look at alternative pre-em herbicides across a range of soil types.”
Work carried out by Hutchinsons on silt soils near Boston, Lincolnshire explored the efficacy of a range of pre-emergence herbicides, as both straights and combinations.
Darryl explained: “When we applied just straight products, all trials plots showed some gaps in their weed control spectrum, but they were still controlling the majority of weeds.
“However, as soon as products were used in combination, weeds were 100% controlled without metribuzin.
“This means, from a silt and sand land point view, I don’t think the loss of metribuzin if it eventually comes will have a huge effect on pre-em weed control. However, it will increase the cost because metribuzin has been the most cost- effective treatment for a number of years.”
Where the challenge may come is on peat soils where growers typically incorporate metribuzin, he added.
“As it stands there are no other options that are approved for incorporation so we are hoping we can get some of the manufacturers to look at this.”
Work is also being done on post-emergence herbicide crop safety across more than 25 varieties. Levels of vigour reduction, necrosis and chlorosis are being assessed post-application, to create a traffic light system for crop safety, explained Michael Rodger, trials coordinator at Richard Austin Agriculture.
“While you may not wipe a crop out, when a crop is stressed by herbicides it is more likely to get secondary diseases.
“Crop responses to the herbicides are variety specific and heavily affected by climatic conditions. We have seen very different results over the three years these trials have been carried out, highlighting their importance.”
Bio-nutrition
Like many farms across the UK, drought conditions are further challenging the growing season in Lincolnshire, and water availability across the site is starting to dwindle. However, this presented some opportunity to demonstrate the benefits of using biological nitrogen in a droughty season.
Nitrogen fixing products, BlueN and Vixeran, which can fix up to 30kg/ha of additional nitrogen, were applied to crops that had received the field standard nitrogen rate, to determine if there was a beneficial impact on yield at the end of the season.
Michael said: “These products do appear to give a bit more resilience to the crop, particularly in dry seasons where they fix nitrogen consistently irrespective of the climate conditions.”
Concentrated seaweed product, SuperFifty Prime is also part of the trial, which offers no additional nutrition but primes the plant to better cope with abiotic stress.
Michael said: “We’ve seen some really positive results in the last couple of years in sugar beet and carrots, but potatoes seem to be one of the most responsive crops. Last season the trials saw a 4t/ha yield response from the product.”
Potato cyst nematode
As well as trials plots of more than 20 different varieties to assess their impact on PCN populations, the agronomy firm is also exploring how the use of biological products could aid varieties with low PCN tolerance to better cope with the pest.
This includes arbuscular mycorrhizal fungi (AMF), which is typically used to improve soil biology.
Michael explained: “AMF has a symbiotic relationship with the plant – it takes carbon off the plant and can enhance nutrient availability. It can also increase nitrogen and phosphorus uptake. For PCN, it can improve tolerance of a potato crop because it is improving overall plant health.”
However, the healthier the plant, the more likely it is to increase PCN numbers, so variety choice is Important, he caveated. The plots are using the variety Innovator, which has poor tolerance to the pest, but high resistance which means it will reduce numbers in the soil.
“The idea is, where you might only have Velum Prime as your one and only in-furrow nematicide application, we’re seeing if we can use a variety you wouldn’t usually be able to and bulk up the yield through these products”
The second plot is assessing Velum Prime applied in-furrow, and the third plot is a combination of Velum Prime and a coded biological treatment that Hutchinsons is exploring.
Michael said: “The product claims to help with water retention in stress situations. We’ve also noticed when it’s used with Velum Prime it seems to improve the efficacy slightly.
Out of all the treatments, the latter is looking the most effective, but full yield and PCN test results will be reported in the new year.
The leafhopper challenge
Researchers are further exploring a common insect which has been around for hundreds of years, but is causing growing concem across potato crops in Europe and the USA.
This is because certain species of leafhoppers can vector phytoplasma – a specialised group of bacteria that cause virus-like symptoms in crops, explained Martyn Cox of Blackthorn Arable.
Physical symptoms of feeding from the pest present as reduced leaf area towards the end of the season in some varieties, which is usually misdiagnosed as disease or malnutrition, said Martyn.
“We know what leafhopper damage looks like in herbs, but in potatoes it’s largely ignored still They are not being associated with damage, but in America trials saw one variety had a 60% yield loss due to leafhopper damage, while another variety had none,” said Martyn.
*Although the leafhopper species responsible for the damage seen in these trials is not present in this country, with hundreds of species of leafhoppers in the UK, and thousands globally, we need to identify if there are differences between the species as far as physical damage to potatoes is concerned,” said Martyn.
Cambridge University Potato Growers Research Association (CUPGRA) work carried out last season found a significant difference in leaf greenness on crops protected by mesh where the pest was present. However, the mesh caused damage to the crop so yield impacts could not be assessed.
“There is potentially a massive difference in tolerance to the pest between varieties – last year one variety was basically speckle-free and another in adjacent plots was heavily damaged.”
The main threat to growers from insect feeding is the transmission of potato stolbur, which although not known to be present in the UK, has been found in Belgium, Germany and Eastern Europe.
“Symptoms of stolbur in the foliage can resemble common problems seen in potato crops but the effects on tubers are seen as soft, rubbery tubers and high sucrose leading to very dark fries.”
The presence of certain perennial weeds such as field bindweed enables the pathogen to survive and then re-infect the vectoring leafhoppers.
Last season Martyn caught up to 1,000 leafhopper insects a week in traps, however, this season’s hot, dry weather has resulted in lower levels of both adults and nymphs in crops, he said.
While the pest is something for growers to remain mindful of, it is not reason for panic, added Martyn.
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