With the strong awareness that blight populations can develop and spread very rapidly, it’s more important than ever that growers don’t become complacent with their blight strategies for the season ahead – even if they have what they believe to be a robust and thought-out programme. Hutchinsons agronomist, Darryl Shailes, is urging growers of the need to be responsive with their blight strategies as the 2010 season kicks off. “Blight populations are changing,” says Darryl. “The now widespread ‘Blue 13’ strain is continuing to dominate the A2 mating type as the strain of greatest significance and concern for growers. However, it’s now also being joined by an emerging A1 mating type strain, found last year, dubbed as ‘Pink 6’ and appears to be just as aggressive as the notorious ‘Blue 13’ and dominating the A1 blight population,” he explains. When it comes to developing blight programmes, Darryl believes that growers are almost spoilt for choice with the fungicides available to them. “We’ve never had it so good with the availability of very good actives against late blight,” says Darryl. “Having said that, growers mustn’t think we have the whole answer when it comes to tackling blight,” he comments. “There’s no point in developing a fully prepared but inflexible blight control programme,” he says. “Blight is very unpredictable,” says Darryl, noting that the last few seasons have demonstrated just how erratic blight can be and illustrated that we just can’t plan ahead and think that is enough anymore. “In 2009 there was almost no blight pressure over in the east at the start of the season,” he says. “Remarkably, we really had to work hard to get any blight in our trials – there was almost nothing until September, with the exception of pressure building for a brief spell in July, but that soon dried out during August. “But then of course the 2007 season is still very fresh in growers’ minds – a reminder of just how rapidly blight populations develop and how fast infection can spread. “Having the ability to be flexible and responsive in your strategy, ready for such a situation again could make all the difference,” he believes. “Despite more recent low blight pressures and the strong availability of blight sprays for use within our armoury, growers mustn’t think they can drop their guard,” warns Darryl, instead advising growers to manipulate the chemistry within their programmes, incorporating products with different modes of action. “Target the product to the disease risk - take into account each product’s strengths and attributes – be it contact, systemic or translaminar activity – and use them, matching the product to the situation, whatever it may be,” he recommends. Darryl explains that if weather conditions were to suddenly change, we could very quickly experience high levels of infection. “Fungicides with characteristics such as persistence and kickback, such as that offered by Valbon (benthiavalicarb-isopropyl and mancozeb), would really show their strength as part of the spray programme,” explains Darryl, also adding that “Valbon forms one of the top four foliar fungicides available for this season, along with Infinito (fluopicolide and propamocarb), Ranman (Cyazofamid) and Revus (mandipropamid),” he notes. With tightened seven day spray intervals now forming the basis of many growers’ strategies Darryl believes that this will still not be enough. “Growers need to be flexible with their application rates, as well as the spray intervals, dependent on the disease pressure and optimise spray inputs – vital to tackle the more aggressive and continually evolving blight strains that are presenting, concludes Darryl. |