Effect of flight activity of stem weevils (Ceutorhynchus napi, C. pallidactylus) and application time on insecticide efficacy and yield of winter oilseed rape

Abstract

During 2010–2012, we monitored flight activity of male and female stem weevils (Ceutorhynchus napi, C. pallidactylus) using yellow water traps, the effectiveness of various application dates for the insecticide thiacloprid (72 g active ingredient/ha), and the influence on yield. The first occurrence of beetles in traps was recorded after soil temperature at 5 cm reached 8°C in all experimental years. In all years, males of C. pallidactylus dominated in the traps and the times of beetles’ first occurrence. The most effective applications of thiacloprid at the stated rate were 14 days (2010), 6 days (2011), and 1 day (2012) after peak flight. Females with eggs appeared in bowls in 2010 and 2012 at first flight, while in 2011 no females were recorded. After the most effective applications, yields increased significantly in 2010 (+5% vs. the control) and in 2011 (+4%), and insignificantly in 2012 (+2%).

Prediction model for cabbage stem weevilCeutorhynchus pallidactylusMrsh. occurrence on winter rape based on an artificial neural network

“…According to other studies, mostly conducted in southern European countries (Sekulič & Kereši, ; Juran et al , ), this occurs only when the temperature rises in the top layer of soil to 9–10 °C. Spitzer et al () reported the first migration activity of adults at soil temperatures (at 5 cm) at around 8 °C. For the almost related species Ceutorhynchus obstrictus , Ulmer and Dosdall () and Cárcamo et al () demonstrated that flight activity usually begins when mean soil temperatures (at 5 cm) fluctuate near 15 °C.…”

Analysis of oilseed rape stem weevil chemical control using a damage rating scale

“…For the cabbage stem weevil a threshold of 10–20 specimens per yellow water trap within three consecutive days is usually acceptable for Central Europe, while for the rape stem weevil a threshold of ten specimens per yellow water trap within three consecutive days is used . Other authors mention different thresholds of 4–6 rape stem weevil specimens and 12 cabbage stem weevil specimens for the same monitoring conditions . Owing to practical difficulties for agricultural producers to separate the two species, thresholds in some regions are given as one value of ten specimens per yellow water trap within three consecutive days …”

“…Because of the complex influence these insects have on oilseed rape, it is often hard to make appropriate assessments of insecticide efficacy. Usually this is done by counting the larvae in plant stems, 9,14,16,34 -36 by counting the number of imagoes on plants, 36 by dissecting plants and measuring tunnels 10,37 and assessing damage. 16,38 It is also possible to carry out assessments by counting the number of exit holes on stems.…”

“…10 Other authors mention different thresholds of 4-6 rape stem weevil specimens and 12 cabbage stem weevil specimens for the same monitoring conditions. 9 Owing to practical difficulties for agricultural producers to separate the two species, thresholds in some regions are given as one value of ten specimens per yellow water trap within three consecutive days. 10…”

Developing a decision support tool to forecast the abundance of the cabbage stem weevil in winter oilseed rape

“…Especially, winter oilseed rape (WOSR) (Brassica napus Linnaeus) is threatened by a large number of different pest insects during the season (Williams 2010). The cabbage stem weevil [Ceutorhynchus pallidactylus (Marsham, 1802)] (Coleoptera: Curculionidae) appears all over Europe causing substantial yield losses (Juran et al 2011;Spitzer et al 2014). A detailed overview on its biology is given by Williams (2010).…”