Relative importance of fumigation in integrated management of stored-grain insect pests in some EU countries (France and Germany)

Abstract: Fumigation with phosphine remains one of the key methods in controlling pests in stored grain. Additionally carbon dioxide and nitrogen with some residual oxygen serve this purpose to a lesser extent. Various other chemicals and methods complete the whole spectrum of integrated pest management where fumigation often presents the last option after other alternatives have failed or do not present feasible options. Grain especially in bulk as stored in silo bins or granaries over several months or even some years is target for some specialised species of insect and mite pests. Prevention, detection and control of these synanthropic pests are difficult and hardly complete. Fumigation offers an economic possibility of thorough disinfestation without moving the grain. Phosphine as a grain fumigant is threatened by resistance of progeny of sublethally treated insects. A quick test for resistance has been developed by Reichmuth to offer practitioners the opportunity to determine the degree of tolerance towards phosphine of occurring insects prior to fumigation. Proper adaptation of the dosage according to this degree of tolerance or resistance still allows complete control the pests.The situation with phosphine in France and Germany is presented. In France, despite registration of the fumigant phosphine, contact insecticides like deltamethrin are regularly preferred as protectants to avoid later infestation of prophylactically treated grain. This prophylactic approach is not in accordance with the German food law. Therefore in Germany, contact insecticides must only be applied after infestation. Since the movement of the grain after detection of insect infestation is costly, fumigation of the stored grain, preferably with phosphine, is the method of choice. Tablets, pellets, bags, blankets, strips and plates, as well as of pure magnesium phosphide and cylinder gas (phosphine in nitrogen), are registered.