There’s a good selection of active ingredients to keep blight at bay, but understanding which is the right active to use and when to use it is essential, growers are advised.
Keeping blight at bay Protecting crops from the ravages of blight will be a key priority for many potato growers over the following weeks and months. Dominic Kilburn seeks advice from specialists in the field. Norfolk-based specialist potato adviser, Andy Alexander (right) makes no apologies for repeating a similar message to growers each season when it comes to safeguarding their crops against blight. Growers, he says, must heed the advice of specialists when they say that a robust programme at the right time, with correct spray intervals, is key in keeping out the yield-robbing disease. “There’s a good selection of active ingredients available to apply to crops this season to keep blight at bay, but understanding which is the right active to use and when to use it is essential,” he stressed. Andy says that he gets exasperated when he hears some growers judging product use by cost, rather than what it can do in terms of controlling blight, and,
with crops worth as much as £6,000/ha, he questions why anyone would quibble as to whether they can save £10/ ha with a cheaper product. “Products must be used for what they can do, not what they cost,” he added. Another concern ahead of the new season for Andy is the planned longevity of some blight spraying programmes. He says that he will keep on with the full blight control programme “until the crop is dead”. “Growers mustn’t take their foot off the pedal before the end of the season. Some of the tuber blight issues I saw last season in the west of the country were a result of exactly that; programmes weren’t seen through to the end,” he explained.
Late blight According to Andy, incidences of alternaria (late blight) are
Incidences of alternaria are becoming more prevalent each season.
becoming more prevalent each season and while work is on-going in attempting to better understand the disease, it’s something that needs careful monitoring in crops. “It’s not something we were concerned about 10 years ago and we are certainly on a learning curve at the moment, and I’ll be feeding samples of the disease through to NIAB during the season to help with research,” he said. Andy suggested that although the disease is variety-specific, from his observations, a crop that is stressed through field compaction, for example, is likely to be more susceptible to alternaria. “It might also be the case that alternaria produces a latent breakdown of tubers in store. This is something I haven’t got hard evidence of at the moment but I am certainly looking closely at it,” he pointed out. “Being proactive with a foliar applied nutritional product, which can be tank-mixed with a blight fungicide, can help A crop that is stressed through field compaction, for example, is likely to be more susceptible to alternaria.
reduce incidence of alternaria and is something I will advocate. However fungicide mancozeb offers good protectant activity and will therefore play a part in some of my programmes this season. “Last season alternaria came in early putting crops under pressure and then bad weather made it difficult to get on the land to spray,” he added. Andy also reminded growers ahead of blight applications this year to be very aware of any field buffer zones and what that will mean in terms of product use.
Weather events As well as 2016 being remembered for having a cold spring, Andy said high impact rainfall events resulted in a testing season for some growers in East Anglia and further up the east coast of England. “It’s highly unusual for our region, but these localised storms caused fields to slump and for crops to be decimated. “One of these extreme rainfall events occurred on a farm near Norwich where 30mm of rain was continued over...
20 www.farmersguide.co.uk May 2017
1-33 ROP may.indd 20