Alternative to azadirachtin to control Dysaphis plantaginea Passerini (Hemiptera: Aphidae) in organic apple production
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The rosy apple aphid, Dysaphis plantaginea Passerini (Hemiptera: Aphidae), is a major pest of apple trees. In organic apple production, this aphid is commonly controlled by spraying azadirachtin, targeted against fundatrices in spring. However, this is the only active ingredient that has proved effective for the management of this pest in organic production, and therefore it would be desirable to provide other alternatives. In this study, several treatments (pyrethrins, garlic extract, kaolin, potassium salts of fatty acids, and defoliation) applied in autumn to prevent or reduce the presence of winged forms and oviparae in the trees were compared. In addition, applications of paraffin oil and lime sulphur in winter against rosy apple aphid eggs were tested. The trials were carried out in Catalonia (NE of Spain) from 2005 to 2010. The results showed that pyrethrins reduced the presence of rosy apple aphid oviparae but they did not have a knockdown effect. The time of application was crucial since the spring infestation was kept under control only when pyrethrins were sprayed throughout the period when oviparae were in the apple trees. It was demonstrated for the first time that pyrethrins sprayed in autumn can prevent outbreaks of rosy apple aphid and can therefore provide an alternative to azadirachtin. As a result, the rosy apple aphid can be successfully managed in countries where azadirachtin is not approved and the likelihood of development of resistance will be reduced since more than one active ingredient will be available for the control of this pest.