New SDHI fungicide Vertisan with triazoles and chlorothalonil will give cereal growers a valuable boost
The rate and mixing partner flexibility of the new SDHI fungicide Vertisan (penthiopyrad) with triazoles and chlorothalonil will give cereal growers a valuable boost to spring disease control options in what could possibly be a high disease risk season, says Yorkshire-based Frontier agronomist Stuart Campbell (left).He says that 2012 was one of the worst disease years on record for septoria and following on from that in 2013 growers had no idea what to expect. Rate flexibility with Vertisan allows growers to adjust fungicide programmes according to disease pressure and season.”Most cereal crops will be more forward by the spring than they were at the same time last year because better establishment generally means more tillers and thicker lush crops,” says Mr Campbell. “But, disease pressure is likely to be higher as a result, especially eyespot which can often be more of a problem in early drilled crops. Seed rates are also up on last year in anticipation of a difficult winter which again may lead to higher stem base disease pressure.”Eyespot can be identified by browning on the base of the stem, but in the early stages it can be confused with fusarium until the lesions appear for correct diagnosis to be made. Where eyespot is a problem we will apply Capalo (epoxiconazole + fenpropimorph + metrafenone) at 0.5-0.75 litres/ha at T0, the key being to stop the disease from entering the stem before GS31. This could then be followed by a T1 treatment based on Vertisan.”Up until 2012 there were only co-formulated SDHI fungicides available which meant growers had much less flexibility in the rates of both it, and the mixing partner,” says Mr Campbell. “Mixing Vertisan at 0.75 litres/ha with Prosaro (prothioconazole + tebuconazole) at T1 gives very good levels of control of key diseases such as eyespot, septoria and rusts, with penthiopyrad having both curative and protectant activity and the flexibility to adjust the Prosaro rate to match the disease pressure. Further flexibility offered by penthiopyrad allows the mixing of chlorothalonil with it, which is not possible with all the SDHIs. This means chlorothalonil will also be added to the T1 mix providing an anti-resistance strategy.”In addition to this he says Vertisan’s unique physiological benefits could give cereal crops a much needed boost if they suffer another poor establishment year.”It came just at the right time for the 2013-harvested crop,” he says. “Evidence suggested improved rooting from penthiopyrad so it was used as the SDHI of choice for the T1 timing in 2013 and should we suffer a long cold winter restricting root growth it could again be an important consideration for next spring.”2013 was a low disease pressure year and so in some situations Mr Campbell was able to be flexible on the choice of triazole partner, however, even in the absence of disease it makes economic sense to also use penthiopyrad because of the physiological effect, which he says pays for itself in extra yield.Barley product choice
Cereal fungicides give the biggest return of any crop input but the difference between a good and a bad programme could be as much as 1t/ha in barley, so it pays to focus on product choice, application timing and robustness.That’s the message from Yorkshire-based Frontier agronomist Alistair Bell (left) who welcomes the addition of the new single acting SDHI active to the fungicide stable because of the much improved rate flexibility that it offers when mixed with triazoles compared to current co-formulated options.
“I can now alter the rate of the mixing triazole partner depending on disease risk without having to change the rate, and potentially compromising the performance, of the SDHI element of the programme,” says Mr Bell. “In 2012 Vertisan brought a valuable new active to Frontier’s cereal fungicide armoury alongside fluxapyroxad (Ceriax) and bixafen (Siltra).” In addition to the control of diseases such as rhynchosporium, ramularia and net blotch, penthiopyrad offers physiological benefits which in independent trials have been shown to boost rooting and give extra greening.”Even early drilled and healthy plants can benefit from extra rooting, especially on light land,” he says. “I look after fields with blow away sand so maximising rooting gives cereal crops the best opportunity in drought-like conditions.”Before SDHI chemistry was available Mr Bell relied on strobilurins and triazoles to tackle the key diseases in barley but when timings were stretched the lack of curative activity compromised control.
He applied Vertisan to barley at T1 in mixture with prothioconazole to control rhynchosporium, net blotch and mildew. In moderate disease pressure situations he increased the rate of the triazole but kept the rate of penthiopyrad at 0.6 litres/ha. If disease pressure was intense then the rate could always be increased. Vertisan is offering much greater persistency along with the triazole partner than can be achieved from older chemistry. “The objective of the T1 spray in barley is to keep all the leaves clean from GS32 second node detectable and then for the T2 spray to keep the awns clean from GS49 onwards. The flag leaf is very small in barley, but it’s the awns that give the yield potential,” he says.Mr Bell says growers’ keenness to avoid a repeat of poor establishment in 2012 has seen many of them bring drilling dates forward, followed by a mild autumn which has resulted in some very forward barley crops which are already showing early signs of disease.As a result, he applied an autumn triazole fungicide application for early drilled crops that were thick and a T0 triazole is planned for most crops in the spring. The curative and protectant activity of Vertisan plus a triazole at T1 timing followed three to four weeks later at T2 with another SDHI-based spray should keep mildew, rhynchosporium and net blotch out of the crop during the key yield making period, he says.”I will use two SDHI’s in my barley fungicide programme because of the improved disease control and physiological effects,” he says. “I used Vertisan on about 60 per cent of my barley last season and this year it will be the cornerstone of my fungicide programmes.”