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Aggressive Blight Strain Too Serious to Ignore – Arable Farming – Darryl Shailes

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Darryl Shailes v2Spring has sprung, although the number of frosts we've had in May does make me wonder. I'm not sure what effect it has had on the blossom on the fruit trees and berry bushes in the garden; only time will tell. The plum and codling moth traps are out so hopefully we’ll have a bit less fruit damage this year.

We've had a first hatch of cygnets and hopefully we'll have also got some young calves in the meadow over the river so, yes, spring has sprung in the Waveney Valley at least.

The recent rains, while very welcome, would have been better without the hail and strong winds, which have hit some crops hard, but they will recover and be better for it, although more rain will be needed soon.

It's been strange walking sugar beet and having to get down on my hands and knees looking for aphids, something I haven't had to do for 20 years or more.

We are now finding thresholds of one green wingless aphid per four plants and the first Biscaya (thiacloprid) has just been applied in the third week of May. Hopefully that will keep them clean for 10-14 days, so I will start looking again shortly. The next treatment, if needed when the threshold is reached again, will be Teppeki (flonicamid) as we must alternate actives as stated in the emergency approval for Biscaya. This is, of course, not only good practice, but the terms of an emergency approval must be followed, so threshold, alternation and water volumes, among other things, must be adhered to.

 

Damage

I must have got taller over the last 20 years as the ground seems much further away these days.

Potatoes are emerging well and I haven't seen as much frost damage as I was expecting, so good news so far.

It's been very interesting looking at how the early irrigations have been wetting up the beds and there are differences depending on soil types and whether the beds were formed dry or wet by the way the water has been infiltrating.

We've even seen that probes are struggling to detect the water moving down the profile so we are looking at a number of ways of helping the water use in a few trials this year. The rain has evened things up though, so it will be interesting to see what happens from here.

Obviously increasing soil organic matter, looking at tied ridges and things such as aqueels will help too, but the beds are already formed and organic matter is a long-term solution and difficult in sands, so we're looking at what sprayer-applied materials can do.

Blight will be the next thing to consider and coping without fluazinam, due to the prevalence of Dark Green 37A2 in recent years, will take some thought. This new aggressive isolate seems to infect tubers and foliage with equal vigour and, although not yet detected in all areas of the country, it is too serious to ignore.

We've also got Light Pink 36A2 which is causing some concern and, while there are no identified resistances as far as I'm aware, it is appearing to be harder to control with all the chemistry available.

Zorvec Enicade (oxathiapiprolin) will be great help in all this as it's the best material we've ever seen in trials and the field reports have been excellent too. The long, hot and dry summer of 2018 meant blight risk was very low, certainly in the East where I'm based, so it was very difficult to see how it performed. But, reports from other areas where blight was still an issue, such as Cornwall, saw Zorvec perform well.

The other actives we have will still play a great part in the programme and we must be mindful of these increasing threats from the various genotypes we have to contend with. When the weather is suitable for blight infection, act accordingly with strong programmes and mixtures of actives, both curative and contact, at suitable intervals to stay in control.

 

Agronomist facts

Darryl Shailes is root crop technical manager for Hutchinsons, with a nationwide remit. He has been working in potato agronomy for more than 20 years.