Application timing and efficiency of acephate and chlorpyrifos for the control of Listronotus dauci (Brèthes) (Coleoptera: Curculionidae) in carrot crops

Abstract

The aim of this work was to determine insecticide application timing and the pesticide efficiency to control Listronotus dauci (Brèthes) (Coleoptera: Curculionidae) in carrot crops, based on adult and oviposition monitoring at the beginning of their activity in spring. The efficiency of acephate (750 g a. i. ha⁻¹) and chlorpyrifos (960 g a. i. ha⁻¹) was evaluated at two different times in Chantenay-Red Core carrot crops. The first application was established after the maximum value in the adult capture curve, while the crop was in the 1-2 true-leaf phase. The second time was established during oviposition, with 40 % and 36 % of the plants infested with eggs in 1986 and 1987, respectively. Results indicate that treatment timing produces different effects on the level of L. dauci damage. A single treatment with acephate or chlorpyrifos during the period of adult capture is not effective to maintain the plants healthy during vegetative growth and to keep the roots undamaged at harvest time. Acephate and chlorpyrifos applied during oviposition can decrease the damage in plants, but only chlorpyrifos reduces the damage in roots at harvest time.