Malathion and Deltamethrin efficacy in controlling Acanthoscelides obtectus say weevil during long storage of beans
Efficacy of Malathion and Deltamethrin contact insecticides in controlling Acanthoscelides obtectus Say bean weevil over a period of 12 months following treatment in laboratory conditions (simulating storage conditions) was investigated. Using appropriate methods (EPPO and other), beans were treated with recommended amounts of Malathion - and Deltamethrin-based insecticide powders. Over a period of 12 months, bioassay was used to determine A. obtectus adult mortality after 2, 7 and 14 days of contact with treated material. Additionally, potential occurrence of F1 generation progeny was monitored over the 14 days of contact with insecticides. The results show that, regardless of the age of Malathion and Deltamethrin deposits, two and seven days of contact with treated beans was insufficient to achieve full mortality of bean weevils, while their mortality was total (100%) after 14 days of contact, the only exception being a Malathion deposit aged 240 days and Deltamethrin deposit aged 90 and 360 days. After 14 days of contact with all Malathion and Deltamethrin deposits on beans and additional 7 days of recovery on untreated material, the mortality of bean weevil adults was total. Weevil adults of F1 generation were found only on Malathion deposits aged 240 and 360 days, while no progeny was registered on Deltamethrin deposits. The tested contact insecticides, applied as powder formulas, can provide full protection of beans from weevils over a 12-month storage period.