A bit like the disease can, the number of blight products seems to have exploded in the past few years. The new generation started with Ranman and Electis, with the likes of Consento, Tanos, and Valbon following on, and then in the past two years, Infinito and Revus.
It has left growers spoilt for choice – no bad thing with blight becoming tougher to control and more aggressive. But we wanted to know how you split the new products apart.
That is why we asked seven experts (see The Panel, right) to rate each product out of five for a number of key attributes (see table), and then rank each in order of recommendation (13=best, 1=worst) for the three phases of blight control programmes, depending on disease pressure. Scores were then averaged to produce charts.
Early-season rapid-growth phase
Infinito, Consento and Tattoo are the expert’s top three choices for the blight sprays during the initial rapid growth stage of the crop.
All three contain propamocarb, which, says John Keer of Agrochemex, is the only usable systemic fungicide, a key requirement atthis timing to protect new growth.
Infinito has the edge, not least because the partnership of propamocarb and fluopicolide is rated by our experts to be the strongest protectant and tops the foliar blight efficacy ratings. It also works out cheaper to buy Infinito than Tattoo, says Mr Keer.
If using Tattoo it is worth watching interval times, UAP’s Barrie Florendine points out. “Don’t stretch intervals, as it is slow-moving in the xylem.” But its kickback activity is underrated. “It’s probably as good as cymoxanil.”
Consento is also quite useful during this stage, he notes, as long as intervals are not stretched.
The big loser in our survey is Fubol Gold. Our experts are mostly steering clear of the metaxyl-M chemistry after results of resistance testing from last summer indicated the A2 strain of blight that dominates the UK blight population is resistant to phenylamides, such as metaxyl-M.
Agrovista’s Mark Palmer is not alone in advocating not using phenylamides given the resistance situation.
The products with the best foliar blight efficacy come to the fore once the canopy is complete, particularly if blight pressure is high.
Excellent protectant activity, together with the kick-back from the propamocarb, makes Infinito the product of choice once the pressure is on. It is best used in blocks of three sprays in that situation, Mr Florendine notes. Remember that a maximum number of four Infinito sprays can be applied in any one crop.
The other three products to consider when the pressure is high are Ranman, Revus and Valbon, according to the results.
Ranman is an excellent product, just lacking some kickback, says Mr Keer. “It has been the mainstay of my programme for many years.”
Revus was only launched last season, so our experts are still finding their feet with it.
But it is a strong protectant and has moderate kickback. Valbon’s curative activity is helped through the use of an adjuvant, ZinZan, says Mr Florendine.
Other products might also be considered when there is high blight pressure, says Les Sykes of Frontier.
“A good protectant like Electis or Shirlan mixed with the best curative product, cymoxanil, would probably be in my top three or four.”
He would certainly be mixing in cymoxanil whenever there was active blight present, regardless of product choice, he says.
When blight pressure is low, one of the older, cheaper materials comes to the fore. Curzate M is a clear favourite overall in this situation.
Interval, rather than product, becomes more important in this scenario, Martin Stothard of Branston says. “But don’t stretch it past 14 days.”
Curzate M is cost-effective when the pressure is low, but it is also fragile, says Mr Florendine.
“You’re relying on mancozeb after two days,” he points out. “Extended use can lead to trouble, and it is shocking on tuber blight. Generally, it is over used because it is cheap.”
Almost all the other products, with the exception of the true systemics (Fubol Gold, Tattoo and Consento) and Tanos, are pretty interchangeable when blight pressure is low, the results show. If you were going to use Dithane, this appears to be the time to do it.
Late-season applications are Ranman’s strength, along with during the stable canopy stage. It is clearly the strongest product on tuber blight, followed by Infinito and Shirlan, according to our ratings.
When there is also late-season blight pressure the superior foliar activity of Infinito also becomes a factor, which is why it and Ranman are almost interchangeable in that situation.
Shirlan makes an appearance as a favoured product at this stage, particularly at lower blight pressure. It is well known to have good tuber blight activity, but its usual rate of 300ml/ha is lacking in foliar blight activity. A higher rate of 400ml/ha has been approved – it should always have been approved at this rate, says Mr Florendine – and does greatly improve blight control, notes Mr Keer.