TRADE AND MARKETING Starch potato cultivation: make it a contest! ‘EARLY BLIGHT COSTS 100 EUROS PER HECTARE’ later.’ Early blight can be controlled by Signum and Amistar. If you want to be certain, the best thing for Phytophthora control is chemicals that contain Mancozeb, says Westhoff. The demonstration fields confirmed this. ‘Mancozeb doesn’t do much for Early blight, but it is enough. At any rate, it appears to be sufficient until the time that the real Early blight remedy (Signum) is needed,’ says Westhoff. It is important that you recognise the spots. This picture shows leaves from a field that is not treated for Early blight. The leaves show a motley of spots. The larger spots, with the characteristic, distinguishable rings, are definitely caused by Early blight. The smaller spots are partly due to Early blight, and partly to other causes such as virus infections. Optimum Early blight control pays, says Bert Westhoff of the crop protection chemical manufacturer BASF.‘At Aveka, Early blight easily costs 100 euros per hectare net, because the crop yields fewer kilos. The crop dies off two weeks earlier and that means 10 to 20 grams less underwater weight. All in all, it costs 5 to 10 percent payout weight.’ At the demonstration field, he shows us a trial plot with Seresta, Aveka and Festien, a part of which was not Early blight controlled. The differences were the greatest in the Aveka crop. In the picture, Westhoff is seen just about on the dividing line of untreated (in front) and treated (behind) crops. ‘An early variety shows Early blight first, especially if it is also stressed as a result of tight nitrogen fertilisation, for example. Aveka therefore shows the greatest differences. Seresta follows a week later; Festien also shows differences, but then three to four weeks I PREFER BETTER PAYMENT. Harmannus Begeman is a crop farmer in Nieuwe Pekela. He cultivates 65 hectares of starch potatoes, which includes his own seed potatoes. He doesn’t think the 100 tons per hectare mentioned by PPO director Ton van Scheppingen is realistic. ‘I assume that he’s talking about payout weight. That means a yield of 70 tons with an underwater weight of 550 grams’ , Begeman calculates quickly. ‘I’m happy if I regularly raise 60 to 65 tons per payout weight per hectare. I won’t get much more on my old sandy peat soil and with the current varieties. And the weather must be good as well, I get my best yields in relatively wet years. I may be able to get more out of it if I watch the health of my crops even more closely and if I improve my seed potato crop even more. There may be a few other methods to improve my balance. I prefer a slightly lower yield and better payment.’ Potato World 2011 • number 4 25 Pagina 24
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