Temperature dependent effects of insecticides on sugar beet weevil - Bothynoderes punctiventris Germ

Abstract

The aim of the investigation was the assessment of toxicity of different insecticides to Bothynoderes punctiventris Germ. at different temperature (14, 20 and 25?C) under controlled conditions. B. punctiventris adult were exposed to Monokrotofos 20-WSC (Monocrotophos) at concentration 0.4, 0.2 0.1%, Agrometrin 20-EC (Cypermethrin) at 0.05, 0.025. 0.012% and Cimogal (Monocrotophos + Cypermethrin) at 0.1, 0.05 and 0.025% applied at filter paper and fed with treated sugar beet seedlings. The exposition time varied from l to 28 h and was determined upon insecticides toxicity. The effect was assessed upon mortality percentage. The mortality was found to be dependent on insecticide concentration and temperature conditions. After being exposed 18 h at 14?C to Monocrotophos, dependent on concentration applied the mortality ranged from 35 to 63,8%. At 20?C, the corresponding values ranged from 70.8 to 76.3%, at 25?C - from 46.3 to 100%. Under same conditions exposition to Cypermethrin 4 h at 14?C gave mortality from 66.3 to 100% 28.8-83.8% at 20?C and from 1.3 to 55% at 25?C. After being exposed only 3 h to Monocrotophos+Cypermethrin mortality ranged from 10,0 to 68.8% at 14?C 27.5 to 98.8% at 20?C and 1.3 to 37.0% at 25dC. The highest mortality of B. punctiventris adults was induced by Cypermethrin at 14?C, with Monocrotophos at 25?C and Monocrotophos + Cypermethrin at 20?C. It was concluded that temperature conditions dictate the choice of insecticide for B. punctiventris control. The environmental conditions during applications are of vital importance for successful control.