SCOTTISH fruit farmers were given an insight into a chemical-free way to keep their strawberry crops free from debilitating powdery mildew disease at last week’s Fruit for the Future event, held at JHI, Dundee.

Increasingly under pressure from supermarket buyers to reduce the use of chemicals, one pioneering way forward is to treat crops with UV-C light using robots during the night.

The fungicide-free method was detailed at the afternoon event by Peter Melis, from the Belgian research centre, Proefcentrum Hoogstraten. He said that current methods of control of mildew can use up to 10 sprays of fungicide per season, but with pressure growing from retailers to reduce the use of chemicals, using UV-C light for disease control was being shown to be effective.

“The biological approach is very labour intensive, but what we have been working on is a robot which will bathe the crop in UV-C light during the night and if done at the right levels, it has been working,” he said.

Powdery mildew is seen as a perennial problem for fruit growers and from 40-100% of the crop can be affected under favourable conditions for its spread. Even spraying can be a causal agent and conventional control methods can cost €2500-€3500 per ha.

In contrast, the UV-C method uses six control lamps per wheeled robot – at around €20 per lamp – plus the capital cost of the robot and powering it up. Payback time for investing in the kit, he guessed would be five years. The optimum dosage has already been established at 110 joules per square metre, with the robot light ‘sprayer’ heading up the rows of soft fruit at 1.1 km per hour.

“Growers in Belgium and here are clamouring for this to come on to the market and the only thing that is holding us back at the moment is working out some technical issues with how the robot travels between the rows and turning at the end,” he said.

“We can’t use GPS because of the metal in greenhouses which disrupts the signal. It may be that we will need a wire-based system.”

Also at the event, Nikki Jennings and Susan McCallum, respectively highlighted the latest developments in raspberry and blueberry breeding programmes.

On rasps, Ms Jennings said that its five-year breeding programme, largely funded by ScotGov, was unique in that all new varieties were underpinned by science and are all available to every fruit grower in the UK.

A move to a new rapid selection process – which could use JHI’s new vertical farming processes to speed up growth and ‘change the seasons’ – would underpin and speed up variety selection, she added.

As it is, JHI is scrutinising three new raspberries at the moment – one early and two mainstream varieties – with a view to them joining the successful Glen Carron variety, which has taken the industry by storm in one year since its commercial launch.

But high yielding and easy picking do not overshadow ‘taste’ in the list of objectives, she added.

Ms McCallum’s blueberry project is still a fledgling operation at JHI, but already appears to be bearing ‘fruit’. “From a selection of 1200 last year, we have whittled this down to 50 varieties for an advanced selection process,” she said.

From those 50 varieties, Ms McCallum said that the end game could be just two or three varieties once they’ve gone ‘through the mill’ – and three to five years before any new variety is released.

Alongside that, the JHI team were breaking down what makes for a successful crop, including how to make the most of available light and working on the production of a specific substrate in which to grow the crop.

“At the end of the project, we hope to offer suitable varieties for the UK and included in that will be husbandry techniques, including the substrate as a package,” she said.