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Is your seed treatment technique good enough?

2 August 2011

Seed potato growers could avoid losing themselves a small fortune in chemicals and greatly improve disease control by paying more attention to their seed treatment technique.

“A lot of seed treatment applications are not very effective, all because operators are not paying enough attention to detail,” says Dr Stuart Wale, head of crop services at SAC.

“Fortunately, by following some simple, basic steps things can be greatly improved.”

Often, just 10-25% of the target dose reaches seed tubers, says Dr Wale. Poor tuber coverage is also common, risking unnecessary disease development.

There are five key questions to address, he notes:

• Is the equipment calibrated correctly?
• Is the spray pattern correct?
• Are tubers clean?
• Is the roller table full of tubers?
• Are tubers rotating at least twice under the spray mist?

Ideally, operators should calibrate equipment between each seed stock, he notes. “However, store managers are usually too busy. But they should certainly calibrate at least at the beginning of the year – it is simply a matter of measuring the throughput of seed passing over the table in a given time, the output from the spray equipment, and adjusting dilution of the chemical solution accordingly.”

A good spray pattern is vital to achieve effective tuber coverage. Nozzles can be in use for 8-10 hours a day for months, so they are likely to wear faster than field sprayers, he advises.

“It’s easy to check how effective the spray pattern is, by popping some blotting paper underneath the nozzles. You want to see an even distribution of regular-sized droplets.”

Dirty seed must be avoided. “Seed treatment will only work if it reaches the tuber surface. This means tubers need to be clean of soil.”

Keeping the roller table full of tubers will also ensure chemical hits the intended target, rather than being wasted on the table itself, says Dr Wale.

“This can be a problem when seed is being graded heavily, which creates gaps. Installing a hopper to allow seed to be released uniformly will overcome this.”

Seed needs to rotate at least twice while passing through the spray mist to help promote even coverage, he adds. “Uniform application is the most important thing.”

Taking these few steps will go a long way to improving application techniques, Dr Wale maintains.

“If I were spending the equivalent of £5/ton chemicals but only applying a fifth of that to the actual tubers, spending a little time going back to basics has to make sense.”

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