By A Correspondent
A potato planter operator nowadays can have a lot to look after.
Apart from steering the tractor precisely there can be fertiliser and nematicide applicators to keep an eye on – and that is not to mention making sure the potatoes themselves are accurately placed.A potato planter operator nowadays can have a lot to look after.
There is, however, a good argument for attaching a piece of kit to apply fungicides. Neil Thompson, product manager for Bayer, told a recent growers’ meeting at Dundee that the fungal disease, rhizoctonia, might not cause total yield loss but it can wreak havoc in financial terms. The need for accurate application made it well worth investing in a purpose built powder applicator for his company’s Pencycuron product, he said.
The most obvious symptom of rhizoctonia in the lifted crop was black scurf with consequent high pick off rates or rejection. The cosmetic effect was enough to make a crop unsuitable for packing and the fungus was also implicated as the cause of silver scurf infections.
“Rhizo spreads from fungal resting bodies either in the soil, or on the seed,” said Mr Thompson. “The effect is easily seen in the field either as random plants or in patches. Stem cankers stop the flow of nutrient into the plant giving that typical stunting and leaf curling of the aerial parts. It can also cause stolon pruning which causes mis-shapen and variable tubers. Tuber dry matter can be affected too, which is a problem for processors.
Greg Dawson, of Scottish Agronomy, told growers that 2010 had been a difficult season with cool soils, slow plant growth and nematode damage all proving favourable for rhizoctonia infection.
“We saw a lot of cracking and deformed tubers last year, especially in the variety Saxon, with pick-off rates as high as 30-40%. It could have been caused by stop-start growth but it really needs a point of weakness such as a nematode wound for the infection to enter the plant,” he said.
Seed could be infected without any visible signs, especially if the fungi were concentrated on the tuber eyes. Tests could be carried out on seed but field scale soil testing was difficult because of the concentration of infection in patches rather than whole fields.
Growers keen to reduce the risk of black and silver scurf have been using Bayer’s Pencycuron products for long enough, but simply sprinkling the powder on to the top surface of a box before it was tipped into the planter was unlikely to be accurate enough, suggested Mr Dawson.
Application rates could be cut from 2 kg per tonne to 1 kg and Amistar added as a spray at 3 litres per ha. This gave excellent control over skin quality, but there could be delayed emergence due to plant stress making accurate dosing all the more important.
Mr Dawson warned of the importance of keeping boxes contaminated with Pencycuron powder separate from boxes used to store ware potatoes. Effectively, this could be seen as an illegal application.
As an answer to these problems, Bayer engineers have collaborated with manufacturer Team Sprayers to develop a commercially available applicator which bolts on to the side of the planter. Small diameter augers deliver powder into the seed hoppers and dispense the powder very close to the point where the cups pick up the seed. The auger pulses at a speed relative to forward travel and seed rate ensuring a very accurate application rate without waste.
For the future, Bayer is working on a new tuber treatment based on the novel fungicide penflufen. It only needs 2gm of active ingredient per 100 kg of tubers and has been showing better levels of control than Pencycuron.
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