Wicked weedkiller

日期:2019-03-07 05:03:06 作者:乐砉伍 阅读:

By Andy Coghlan A FUNGUS that grows best on tomato juice looks promising as a herbicide for organic crops. The fungus kills fat hen—also known as pigweed—a weed which is a serious problem for European farmers. In greenhouse trials at Aberdeen University’s Centre for Organic Agriculture, researchers have shown that the fungus can vanquish the weed—if spores are applied at the right time. “Fat hen is the number-one weed affecting at least 10 major crops in Europe,” says Wendy Seel, head of the Aberdeen team. Conventional farmers control it with chemical herbicides such as atrazine, but the weed often develops resistance to them. Organic farmers use careful crop rotation and ploughing to control fat hen. “If you’re careful enough, you can control anything, but fat hen seeds are very persistent in the soil, and can re-emerge at any time,” Seel says. A benign biological control agent would give growers more options. Seel and her colleagues say the fungus, Ascochyta caulina, already infects fat hen, and coexists with it across a broad range of climates, from Iran to Norway. To get a fungus to kill the plant, early treatment is essential. “Strike early on, otherwise the plant outgrows the fungus,” Seel says. “You need to get it within 12 days of it emerging from the soil.” The other requirement is for moisture, so that the fungal spores germinate and infect the weed’s leaves. “If you sprayed in dry conditions, you’d need some way of keeping a film of water close to the fungal spores, perhaps by spraying an oil emulsion in water,” says Seel. Another option is to spray when there is dew on the weeds. In separate experiments, Seel found that the fungus grows best on V8, a commercial brand of tomato-based vegetable juice. “It gives the fungus a good start in life,” says Seel, who presented the work on 18 November at a conference of the British Crop Protection Council. Seel, who is part of a European collaborative team led by Piet Scheepens of the Dutch government’s agricultural laboratories in Wageningen, says that it will be years before the fungus is available commercially. Growers must also be sure the fungus doesn’t harm the crops it’s supposed to protect. Trials on maize are under way in Basel,