Seed suppliers are being urged to protect their high-quality product from storage diseases at first grading following the wet 2024 harvest and reports of symptoms developing in some stores.
Tuber pathogens that develop in seed from harvest to delivery include dry rot, gangrene, silver scurf and skin spot. Once established they are difficult to eradicate, significantly affect seed quality and cause problems in following crops.
To prevent disease development on seed in the first place, application of tuber fungicide treatment Gavel (imazalil) is advised.
There are three phases where a Gavel treatment can be applied; phase one is at harvest or as tubers are loaded into store; phase two is during storage – usually at first grading – and then finally, phase three is when they leave store for delivery.
Disease risk
Frontier’s seed treatment specialist Darren Wonnacott says last year’s wet harvest in some seed producing areas will have increased the risk of these diseases, particularly skin spot and silver scurf.
He’s also seen mummified seed tubers in some stocks, where they were infected with disease and dried out in cold storage: these are now a source of inoculum.
“There is the potential for any inoculum to spread is you get any fresh damage during first grading, so my advice would be to apply Gavel where is hasn’t already been applied in that phase two window.
“Seed supplies are tight this year and values are very high, so it makes any investment in a treatment relatively cheap, particularly as a small problem now can turn into a big problem before delivery. It’s a no brainer for me,” says Darren.
Susceptible varieties
Skin spot is of particular concern this winter in high-risk susceptible varieties like King Edward and Rooster because of conditions during lifting, he adds.
In these high-risk cases, he suggests a combination of Gavel and Storite Excel (thiabendazole) to bolster protection against skin spot, a pathogen which causes poor and uneven emergence in the following crop.
To apply storage fungicides like Gavel evenly over seed tubers Darren advises using a roller table applicator with a rotating hollow cone nozzle and air assisted hooded canopy.
“Always make sure your equipment is set up right and has been serviced and calibrated before use, as it’ll ensure you get the most out of the treatments and keep seed in the best condition for planting.”
