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Novel approach to disinfection delivers

The end of the season marks the start of an intensive clean down programme for many.

Roly Holt of R & L Holt

The end of the season marks the start of an intensive clean down programme for many. For R & L Holt Nurseries in Evesham, with three nurseries totalling 90,000m2 of glass, the magnitude of the task is such that they have adopted a novel approach to disinfection with the application of Jet 5 (peroxyacetic acid) as a fog, with great results.

For Holt Nurseries who supply tomatoes to a number of the major supermarkets as well as local stores and farm shops, marketed through Evesham Vale Growers, the need for high standards of hygiene is vital. “Undertaking thorough clean up procedures helps us reduce the risk of carry over to next season’s crops. Hygiene is something which we must always be on top of,” says Roly Holt.  

“Thorough disinfection and clean down practices are our foundation. Once the growing season is complete each glasshouse area is emptied, cleaned out to ensure all debris is removed and surfaces washed down,” says Roly.

“Unlike other crops, tomatoes are often in for the whole year. We have just one chance between the turnaround in crops, to have a thorough clean up.”

Last December, once the production site was emptied, John Purslow, of Eagle Services was called in to fog using broad spectrum disinfectant Jet 5.

“It was done as the last stage of winter hygiene practices, before the next plants came in,” he recalls.

“The area being treated was huge, the three separate glasshouses had a combined area of over ten hectares, it was absolutely massive,” says John, noting that typically 20-30 litres of product would be used to fog a store or glasshouse but for this project,700 litres were needed.

Working alongside Certis, the first task for John was to calculate the cubic metres of the buildings being treated and the quantities required to achieve the density of chemical to give effective sterilisation – 10% chemical, with a water vapour appearance.

John ran the two fogging machines down the central concrete pathway of each glasshouse, with the fog dispersed using the ventilation system from this central pathway, in an outwards direction to the perimeters of the buildings.

He explains that by fogging at 500oC the chemical mix comes out of the fog head and immediately provides coverage up to the roof. “While the buildings aren’t tall – four or five metres – there are still areas, a fogging treatment can access, which simply cannot be reached by spraying. As the temperature falls, so too does the ‘fog’ – giving complete coverage.

“After 24 hours, the ventilation system can be opened up, before allowing staff and plants back in.” And two days later the plants came in, he noted.

You’re not restricted at all with Jet 5, notes Roly. “It’s not a persistent treatment, it breaks down very quickly and you can be back in after just 24 hours.”

There are clear advantages with fogging over spraying which both John and Roly recognise. “It reaches all those nooks and crannies which you cannot get to with a wet spray,” says Roly.

“It has done a good job, preventing contamination from any remaining material in the glasshouse to the next batch of plants.”

It’s ideal as a broad spectrum treatment that’s effective at reducing and preventing bacteria, viruses, fungi and algae build-up. “Jet 5 really is a valued product. It’s been successful. And has the flexibility of use as a liquid to sterilise trays and production equipment,” says John.

Jet 5 can also be used as a drench or dip to clean crates in packhouses to prevent contamination and can be used to sterilise benches, tools, structures and irrigation lines.

John comments that when you think how much money is invested in these sites, it’s got to pay to spend the time and money between production cycles, to sterilise and have the best possible starting conditions.