Forecasting the breaching of the control threshold for Ceutorhynchus pallidactylus in oilseed rape

Abstract

1 The cabbage stem weevil Ceutorhynchus pallidactylus (Mrsh.) (Col.: Curculionidae) is a common pest in oilseed rape Brassica napus L. throughout Europe. 2 The abundance of the cabbage stem weevil was monitored in field surveys by using yellow water traps between 2007 and 2012 at five locations in Luxembourg. We forecast the abundance of the cabbage stem weevil at levels above the control threshold in oilseed rape in springtime. 3 If mean winter temperatures between 5 and 13 February are closer to 4.0 ∘ C than to −2.4 ∘ C, no breaching of the control threshold is to be expected in the subsequent March. The monitoring effort might be saved in those years. 4 Leave-one-out cross-validation revealed that whether the control threshold was exceeded could be correctly predicted based on the observed temperature differences identified in 22 out of 27 cases (81.5%) in the present study. 5 The present approach can be easily transferred to regions where air temperature data are available, although it should not be used without prior local validation.

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

“…Table 9 shows the mean temperatures during the two critical periods. It can be seen that in the year with the lowest stem weevil abundance (2011) the mean temperature was 5.14 ∘ C in the first critical period and 2.67 ∘ C in the second, which is in accordance with the findings of Eickermann et al 32 Similar mean temperatures for the mentioned period (4.02 and 2.46 ∘ C) were recorded for 2013, which was also a year with a lower pest abundance; however, the threshold of ten specimens per yellow water trap within three days was breached. In 2010 the mean temperatures for the mentioned periods were −0.22 ∘ C and −1.06 ∘ C, which had positive effects on the insect survival, while in 2012, owing to frost problems and yellow water trap malfunctions, the obtained results were not reliable.…”

“…Each insect species has a different response to environmental conditions. In a recent trial it has been proven that the winter survival of the cabbage stem weevil is greatly affected by higher temperatures during winter diapause . Higher than average temperatures negatively affect the survival of overwintering species by activating the specimens prematurely, which accelerates the depletion of stored nutrients and leads to starvation .…”

“…Higher than average temperatures negatively affect the survival of overwintering species by activating the specimens prematurely, which accelerates the depletion of stored nutrients and leads to starvation . Eickermann et al . established that there are two distinct periods that affect the survival of C. pallidactilus .…”

“…In a recent trial it has been proven that the winter survival of the cabbage stem weevil is greatly affected by higher temperatures during winter diapause. 32 Higher than average temperatures negatively affect the survival of overwintering species by activating the specimens prematurely, which accelerates the depletion of stored nutrients and leads to starvation. 33 Eickermann et al 32 established that there are two distinct periods that affect the survival of C. pallidactilus.…”

“…32 Higher than average temperatures negatively affect the survival of overwintering species by activating the specimens prematurely, which accelerates the depletion of stored nutrients and leads to starvation. 33 Eickermann et al 32 established that there are two distinct periods that affect the survival of C. pallidactilus. The first period is from day 14 to day 18 (days from the beginning of the year), which regulates the end of diapause, and the second from day 36 to day 44, which controls quiescence.…”