Control of cabbage stem weevil and pollen beetle with one insecticide application

Abstract

Over the course of three years (2016–2018), the effects of insecticides on stem-mining weevils [(Ceutorhynchus pallidactylus (Marsham, 1802), Ceutorhynchus napi (Gyllenhal, 1837)] were assessed under field conditions. The dates for spraying were determined on the basis of the recorded percentages of weevil females carrying mature eggs in their ovaries (timing I: the first females with mature eggs present in yellow water traps; timing II: more than 50% of the females with mature eggs present). Delaying the first spring insecticide application till timing II made it possible to combine the control of the stem weevil along with the control of the pollen beetle, Brassicogethes aeneus (Fabricius, 1775). However, the poor effectiveness of the tested insecticides on the stem-mining weevils, regardless of the date they were sprayed, indicates it is impossible to successfully control the insect pests with one insecticide application during the seasons with prolonged egg-laying periods.