It is important to re-adjust fungicide timings while the weather is conducive to cercospora – Arable Farming
Darryl Shailes, root crop technical manager, gives insight on root agronomy this month ...
The garden is still suffering from the drought. We had some lovely rain last week but unfortunately it only lasted about 20 minutes, with only 4mm falling, and the vegetable beds were still bone dry 2cm down. The one upside of the weather is that the plums are ripening rapidly and we will have a bumper crop if we can get them before the wasps and hornets take too many.
The rain, or lack of it depending on where you are, is still dominating UK farming. Huge amounts fell in a few hours in Lincolnshire – up to 185mm in some places washing out potato baulks – to nothing in other areas, and very little rain is on the horizon.
I have still not seen or heard of any potato blight in East Anglia, although there were some blips last week on the various forecasting methods we use internally at Hutchinsons. Our trials site hasn’t shown any signs of blight yet, so we are still hoping for the weather to change so we might have something to see and show, late September or even October. The site did get 50mm of rain last week and was late planted, so at least the crop will grow well now.
I looked at an excellent unirrigated crop last week in the Fens. The crop we looked at was very bold and a credit to the farmer. However, alternaria was showing up in fields of Markies. We had a long discussion about alternaria control and are sending some lesions away to determine what species it is, if indeed it is alternaria at all.
Irrigation
Where lifting is going on growers are having to irrigate just to get potatoes out of the ground and to get some soil on the web to reduce the damage potential – another cost and logistical hassle.
Sugar beet is variable as can be expected with some crops flat to the ground on hot days and others on better soils hanging on remarkably well.
The British Beet Research Organisation has just issued a cercospora warning and we must all be very vigilant to ensure the crop isn’t further hampered by disease. In 2020 we saw the first big national epidemic of cercospora in the UK and it hit many crops that were already damaged by virus very hard.
This season, by and large, virus has been managed very well either with seed treatments, foliar insecticide or a combination of both.
In the rest of the world cercospora is the major disease and crops regularly get treated five to seven times to keep it at bay.
We now have a better armoury with the introduction of a new product based on a mixture of prothioconazole and fluopyram from Bayer that will be available from September.
It is important to re-adjust our timing with cercospora. Back when the major issue in the beet crop in the UK was powdery mildew and rust, the timing and gaps between fungicide applications were not so vitally important. However, with cercospora, as it is so aggressive and we are mainly relying on the DMI (triazole) component of the fungicide, such as prothioconazole, difenoconazole and flutriafol, they must be applied as soon as disease is first seen and then at a maximum of three-week intervals while the weather is conducive to cercospora.
It is especially important that any new leaf growth that is generated by rain is protected and the sugars allowed to stabilise before the crop is harvested. Getting in too early after significant regrowth of leaf will inevitably lead to a reduction in the sugar in the root as it is remobilised into the leaves.
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