Arable News

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T0 spray – the foundation of any disease control strategy

If growers needed a wake-up call in terms of their cereal disease management, they got one in 2012

If growers needed a wake-up call in terms of their cereal disease management, they got one in 2012. Here, a technical expert says that a change in mind-set is required if crop protection failings last season are not to be repeated in the future. Dominic Kilburn writes.If there is one key message for growers to take on board ahead of cereal disease control programmes this spring, it’s that they must be more proactive in terms of their disease management, and not leave it and get into reactive disease control situations.That’s according to Makhteshim Agan (UK) technical & development manager, Stuart Hill (left) who stresses that the industry faces an uphill task in changing people’s overall approach to disease management in light of poor curative control of key diseases in cereals last year.Stuart suggests that up until last season things had become a bit too easy; successive low disease pressure years and a reliance on chemistry that, on the face of it, appeared to deal with the key cereal diseases when asked of it. “However, as an industry we have tended to use things until they break and we’re not very good at taking a step back and looking at the bigger picture,” he says.”As a consequence, we end up having to react rather than being proactive,” he adds.
Stuart says that last season’s poor levels of disease control witnessed by many growers and agronomists, in particular with that of septoria, was a wake-up call for all concerned. “Current programmes are built around delivering end yield with curative products – this is satisfactory when there is a continuous pipeline of new curative molecules – but now there is the problem of resistance, less curative activity and relatively less new active ingredients entering the market.”The future of cereal disease control hinges around challenging our traditional mind-set. We need to think differently and protect not just our crops but also our chemistry,” he stresses.According to Stuart, a ‘perfect storm’ of different factors, spearheaded by increased resistance to products, is likely to mean that the difficulties experienced last season will increase in the future. “HGCA research shows that there is a shift in the activity of our top two triazoles on septoria and a serious decline in their efficacy in controlling the disease.”Triazoles are still the foundation of curative chemistry but they are beginning to suffer,” continues Stuart. “In addition, future regulation from the EU, eg cut-off criteria, will mean that we may be left with less effective products. Combine this with increasing resistance pressure, that there is serious resistance concern regarding the new SDHI chemistry, and we have a tough challenge ahead.”He points out that, in the UK, increased pressure is being put on ‘single-site’ chemistry – responsible for the vast majority of cereal fungicide applications in a typical season – and includes triazoles, strobilurins and the more recently available SDHIs. “We are putting single-site chemistry under enormous pressure and yet multi-site chemistry, such as folpet (as in Phoenix) and chlorothalonil, which is much less prone to resistance breakdown, is sprayed on a relatively low percentage of crops.”This has to change,” he challenges. “There’s got to be a better mix of actives – multi-site activity and multiple single-site products. In future we should be mixing in a multi-site such as Phoenix, certainly at T0 and T1 timings.”Stuart adds that varietal disease ratings are doing little to help farmers and agronomists in their programme decision making, highlighting that the overall average in terms of septoria ratings for varieties on the 2012/13 Recommended List was 5.2. Almost 80 per cent of the wheat area (2011/12) was sown with varieties with a septoria resistance rating of 5 or less, which is unlikely to help guide choice of fungicide dose, he says.As well as the issue of resistance and reduced curative activity in products, Stuart explains that farm size increases have increased the pressure on timing of applications, even with larger sprayers, and this exacerbates the situation. “Just because there is bigger machinery doesn’t mean that all crops can be covered when they need to be. Additionally growers are trying to drill larger areas earlier in an attempt to get everything in the ground on time, resulting in bigger crops over winter and larger sources of inoculum when we emerge in spring.”It is very difficult to get spray timings accurate on these large areas and it is becoming even more critical to apply programmes as key leaves emerge to gain the most protection of them. We should also be focusing on key growth stages of application rather than the common T0, T1, T2 and T3 numbers,” he comments.
“With all this in mind, we have to become more preventative in our approach,” he adds.Stuart argues that although only half to two thirds of the UK’s wheat crops usually receive a T0 (GS30) spray, an application at that timing should be the foundation of any disease control strategy, otherwise growers end up reacting to disease. “We advocate the use of Phoenix at 1 litre/ha in mixes with triazole chemistry, to build a strong preventative base to our programmes. The cost compared with the potential return is negligible with the addition of T0.
“We are certainly in an insurance situation with a T0 and it puts growers in control for the next part of the programme. With no T0 it’s a long time to a T1, with a significant potential for disease to proliferate.” He also recommends the use of Phoenix at T1 with the single-site products such as triazoles/SDHIs. “In some instances antagonism has been noted with some protectant products but with Phoenix we haven’t seen any issues, in fact quite the reverse. Our studies have shown increased uptake of the triazole partner when mixing with Phoenix and this has led to significant disease control benefits.”T0 and T1 will be the big timings for septoria in the future and it will allow agronomists and growers to adapt the latter half of their programmes.”
Stuart adds that the message about rusts is just as important. “In recent years varietal resistance to rusts has been relatively poor, whether brown or yellow rust.Additionally we see very quick single step mutations within the disease which can render a varietal resistance redundant nearly over night. Although we still have some good curative chemistry with certain triazoles like Cortez (epoxiconazole), with Phoenix we have shown in leaf uptake studies a more rapid increase in uptake of the triazole which has delivered clear benefits in terms of rust control.”Ahead of this spring’s programmes, Stuart points out that winter cropping plantings are certainly down following last autumn’s difficulties and many wheat crops remain in a backward condition. “Growers and agronomists will undoubtedly tailor their programmes to these crops but we need to keep in mind that although they will already have a lower yield plateau, they will need investment otherwise the yield potential will be even lower. Even in these situations applying a T0 and multi-site products will give more control of programmes, and the leaf that is there needs protecting to maximise yield,” he states.Why use folpet in your fungicide tank mix?
Folpet (Phoenix or Arizona) is a 500g/litre suspension concentrate fungicide with label approval on winter and spring wheats and barleys. It can be used up until GS 59, with a maximum individual dose of 1.5 litres/ha and a maximum total dose of 3.0 litres/ha. It should be applied in a water volume of 100-200 litres/ha.Used as early as possible in the disease control programme – at T0 (1.0 litres/ha) and T1 (1-1.5 litres/ha), key on-label diseases controlled are septoria tritici (in wheat) and rhynchosporium (barley). Field trials have shown activity in rust programmes in wheat as well as net blotch, brown rust and ramularia in barley, says MAUK.Folpet builds flexibility into the fungicide programme thanks to its persistent protective chemistry, and there is no known resistance. It does not inhibit partner products and there is definite synergy with triazoles, claims MAUK. Folpet also reduces pressure later in the programme, protecting curative chemistry from resistance.


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