The latest breakthroughs in breeding, pest and disease control, storage and marketing were on show at Potatoes in Practice, held near Dundee. Marianne Curtis and Jo Learmonth report from the event
Care over depth of Vydate (oxamyl) granule application when planting potatoes is key to maximising efficacy of the nematicide and meeting stewardship requirements.
Demonstrated at Potatoes in Practice, the ScanStone bed mixer mounted with a three-hopper Horstine Microband applicator, enables efficient delivery and incorporation of Vydate granules, explained Craig Chisholm, Dupont regional technical manager.
“It is only delivered where required and incorporated immediately. There is an electronic clutch so all stewardship requirements can be met.
“Ideally you have early incorporation down to the depth planted and one of the most reliable ways is to have a bed tiller [mixer] in front of the planter. It should not be applied too far in advance of the planter. The planter doesn’t do much mixing at all.”
Vydate goes evenly through the fish tails and is incorporated by powered blades, said Mr Chisholm.
It is important to set the equipment to deliver granules at or just below planting depth, he added. “Some people plant at 7in and set it to 7-8in. But with early salad potatoes planted at 5-6in you should not stick at 8in otherwise it is a waste of product.
Until recently many breeders focussed on potato appearance and yield, however, the last decade has seen a growing emphasis on end use and pest and disease resistance.
AHDB head of crops export market development, Rob Burns, said potatoes were being bred more specifically for chipping, processing, salads and table as well as to meet requirements of specific export destinations e.g. tolerance of hot climates.
“It is a market of two halves. There is the high end where bigger companies innovate and use new varieties grown for specific uses and growers of more traditional varieties such as Maris Piper.”
With cold storage meaning potatoes can be stored for longer, there comes a greater risk of changes in the sugar profile, creating problems when frying. Breeders are looking at this to improve storage characteristics, explained Mr Burns.
Pest resistance is also receiving increasing attention, particularly PCN pallida resistance, he said. “More and more land is being lost to PCN which is costly to manage. But growers need encouragement to move across as seed costs more.”
Finlay Dale of Caithness Potatoes said several varieties in the top 30 planted in the UK were more than 100-years-old. “Some popular varieties are only there because of the chemicals we are using. They are becoming outclassed. Maybe the market needs to move faster. Salad baby potatoes are 10% of the [consumer] market; they were nowhere ten years ago.”
A new trial shows ferric phosphate is an effective alternative to metaldehyde for reduction of slug damage to potatoes, with timing crucial to maximise molluscicide efficacy.
Dr Andy Evans, researcher at SRUC, who conducted the trial, said: “Metaldehyde is a very good product but it turns up in drinking water catchments. When methiocarb was withdrawn, the natural inclination was to switch to metaldehyde.”
But two trials conducted last year, one in England and one in Scotland, showed ferric phosphate to control slugs as well as metaldehyde, said Dr Evans. “I encourage growers to take it up in confidence it will work.”
The three key timings for molluscicide application are just before the crop canopy meets, around 4-5 weeks later if moisture from rainfall/irrigation is present and at burning down, he said.
Work is ongoing to refine application timings, added Dr Evans. “This year we are trying to be more reactive to weather conditions. We’ll put the first one on and if it rains two weeks later we’ll put another treatment on then, relating it to when slugs come up.”
Development of gene markers allowing breeding of potatoes which store better should be possible in the next 5-10 years.
Speaking at a Potatoes in Practice seminar, Dr Mark Taylor, researcher at the James Hutton Institute, said growing resistance to use of sprouting inhibitors such as CIPC meant there was an urgent need to develop potato varieties with better storage characteristics.
He is involved in a project looking at sprouting in potatoes and onions to see whether there are any common features. “We are trying to understand which genes are switched on at dormancy break and which hormones are released. We can test if a gene is important in a trait and turn the gene off or overexpress it.”
A suite of DNA molecular diagnostics for free living nematode (FLN) species that transmit tobacco rattle virus to potato crops was launched commercially at Potatoes in Practice.
Dr Roy Neilson, nematologist at the James Hutton Institute, said: “Globally FLNs cost agriculture in excess of £100bn per annum, in terms of reduced yield, reduced quality and management of the nematodes.
“In the UK, historically PCN has been the focus in the potato industry but as a consequence of the reduced availability of nematicide in recent years FLNs have been brought into sharp focus.”
There are 30-40 species of FLNs, some of which transmit tobacco rattle virus (TRV) with symptoms known as spraing. Levels of TRV infections over 4% can render entire crops unsaleable, both for fresh and processing markets.
Dr Neilson said: “Annually, we see 30% of the samples positive for TRV and so it is important to correctly identify these nematodes. The new method will cost less than the conventional microscopic process as it is quicker, requiring less manual analysis.
“We have spent three years in validation and initially it will be available to the UK potato industry through James Hutton Ltd.”
Blackleg levels in a following potato crop can vary with different desiccation methods, according to recent trial results.
James Reid, seed grower, said trials carried out over five seasons in conjunction with Scottish Agronomy, looking at haulm burn-down showed that higher water volumes at T1 are important to defoliate the plant to expose stems for T2 applications. “We use 400l/ha water,” he said.
“Over the last two seasons, the weather has been dull, with low UV levels and I think it’s fair to say that diquat needs a little help.”
Mr Reid said the burn-down programme resulting in the lowest level of blackleg in the following crop was: Reglone (diquat) at 1l/ha to 1.5l/ha applied in 400l/ha of water; followed by flailing 5-7 days later. Two to three days after flailing, 1l/ha Spotlight Plus (carfentrazone-ethyl) and 1l/ha Reglone was applied in 300l/ha of water.
A new App for sizing potatoes was on display at Potatoes in Practice.
Chris Thorman, Agrovista agronomist, said: “It is 95% accurate on size grading and 99% accurate on numbers, making it more accurate than riddles.
“You dig 2m of the row and lay the tubers out in a tight group, placing an A4 sheet of paper beside the group, as a template, take a photo, send the photo through the App and it comes back quickly with results giving total number and size profile of the potatoes, in 5mm size bands.”
Dr Matt Aitkenhead, soil scientist at the James Hutton Institute, said: “We estimate that the cost of doing this the traditional way with riddles, in terms of staff, labour, equipment and time is £12-15 per dig. Using the App will cost the grower approximately £1 per photo and saves about 25 minutes per dig.”
The free App has been developed by Agrovista and the James Hutton Institute with funding from Genomia and will be launched commercially in November.