Arable News

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Potato crop challenges continue

Restricted options on nematicide products is one of several key challenges facing potato growers for the 2016 season

Restricted options on nematicide products is one of several key challenges facing potato growers for the 2016 season, highlights a Norfolk-based specialist adviser. Dominic Kilburn writes.

Growing potatoes is a high risk business which requires significant investment during the good times as well as the difficult times – the latter predominating at the moment, says Norfolk-based independent potato consultant, Andy Alexander (below).
He says that the mild winter has caused huge problems for growers with ambient storage systems where they struggled to keep crop temperatures down sufficiently. “The resultant poor quality from stored crops breaking down, and growers having to market them ahead of when they would ideally have liked to, has depressed prices,” says Mr Alexander, who is also a member of the Nematicide Stewardship Management Group representing the independent sector and the NFU.

“In addition, cashflow is a major issue for growers at the moment and other crop commodity prices are doing nothing to help prop up the potato sector,” he comments, adding that, despite the difficulties, refrigerated storage should be seen as a key investment now that mild winters such as 2015-2016, seem to be a regular occurrence.

PCN problems
Perhaps of greatest concern, however, and one with immediate consequences in terms of seasonal planning, he says, is that of a lack of suitable chemistry to tackle the ever increasing burden of potato cyst nematode (PCN), particularly so for growers of early crops.
“Growers should already be aware that there is no Vydate (oxamyl) available this season and, in most cases, they will have to switch to Nemathorin (fosthiazate) for the control of PCN. The big worry for me is that Nemathorin has a longer harvest interval – the crop cannot be sold for 119 days after application – which means it’s not an option for early crops.
A key difference between Vydate and Nemathorin is the way it is applied, he points out; the latter is applied across the furrow, rather than in the furrow like Vydate – see box below for more information.
“With 60-70 per cent of potato growing land infested with PCN, the only thing early growers can do is to find PCN-free land or look to varieties with resistance, although some of these will not have a ready made market as yet,” he says.
Free-living nematodes (FLN), different to PCN, and which can lead to spraing, also have limited control options, he adds.

For those whose cultivations are well underway and about to begin planting, Mr Alexander suggests that waiting for soil temperatures to rise sufficiently will be key in the battle against rhizoctonia (stem canker), which attacks tubers in the cold. “Be patient is my advice and wait until soil temperatures are at a minimum of 6oC at tuber depth before planting begins.
“Do be conscious of compaction too,” he stressed. “Start cultivating at the right time; when land has dried out sufficiently, if root restriction and crop nutrient deficiency is to be avoided.”
With the blight spraying season on the horizon, as well as weed control and slug pellet applications, he warned growers of the complexities of buffer zone requirements and urged growers and agronomists to read the labels carefully this season. “There are new products coming through the system with variable requirements in terms of buffer zone restrictions of anything from 5-10m.
“There’s a huge responsibility on both the operator and the agronomist to get this right or face penalties in the event of an RPA check-up.”
Mr Alexander said that he had written to the Chemicals regulation Directorate (CRD) recently to ascertain whether buffer zone width restrictions could be standardised for the future to simplify potato growing operations.
In terms of blight, he added that it was imperative that growers didn’t become complacent following what was a relatively low disease pressure year in 2015, and that they maintained regular spray intervals with robust programmes as the season progressed.

Mr Alexander also stresses the importance that growers should put on growing crops on a contract basis, something he estimates 70 per cent of growers were doing at the moment. “If it were me, I wouldn’t be involved in a crop unless it was contracted forward. Potatoes are a high risk business and growing 100ha (250 acres) you need some kind of security,” he highlights.
“This is particularly true for the fresh sector where we are seeing changing consumer habits, variable demand and price volatility because of pressure from retailers,” he adds.

Irrigation warning
He also reminds growers of the on-going changes due to reform of the abstraction licencing system. “Permitted volumes that growers are currently used to will not be the same in the future and, if your licence is unused for four years then by 2021 it will be revoked altogether,” he stresses.
“Even those who are trickle irrigating – which in the past has been exempt from licencing – will have to get used to changes as this too is due to become part of a reformed abstraction licence,” he says.
Mr Alexander advises anyone involved in irrigation that is not a member of their local abstraction group to join one immediately in an effort to become “streetwise” and informed as to forthcoming changes.

Main Messages
– Limited nematicide options for 2016 – be aware- Invest in upgrading storage where possible- Wait for soil temperatures to rise sufficiently prior to planting- Avoid compaction with pre-planting cultivation- Get up to speed with proposed changes to water abstraction licenses

Nemathorin know-how
A key difference between a Nemathorin and Vydate application is that there is no in-furrow recommendation for Nemathorin. It has to be broadcast and incorporated across the full cultivated width at, or pre-planting, says Syngenta field technical manager for potatoes, Douglas Dyas.
We have seen consistently good results from a simple rotary machine applying Nemathorin just prior to planting off the bed-tiller, but it can also be done pre, or during, the de-stoning process, he points out.
The ideal depth of application is 1520cm, says Mr Dyas, and the broadcast rate for the control of PCN, or reduction of FLN, is 30kg/ha, while for the reduction of wireworm the rate is 15kg/ha.
Always keep to these rates, he advises, while suggesting that carrying out a rice test prior to application is advisable to check that the granules are being placed where you want them. Growers should also remember to change the cartridge or metering device on the applicator to one suited to Nemathorin-sized granules, he adds.
Harvest interval is 119 days which is put in place to avoid any residue issues and we dont recommend the product for use by early potato growers, he confirms. For those early growers, then integrated pest management including extending the rotation, use of more resistance varieties and PCN-free land, is particularly important, he says.
*More information is available at and from the Nematicide Stewardship Programme (

  • Written by: Farmers Guide
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