Cabbage stem weevil (Ceutorhynchus quadridens) on spring oilseed rape in Southern England and its control

Abstract

S U M M A R YSurveys in 1974-75 in which 20 plants were examined in each of 105 fields showed that cabbage stem weevil was widespread on spring oilseed rape in the south of England, the larvae sometimes infesting a large percentage of plants and reducing vigour and yield. In replicated field trials during 1974-77, infestations were reduced by seed treatments of gamma-HCH or sprays of gamma-HCH, azinphos-methyl, azinphos-methyl + demeton-S-methyl sulphone, chlorpyrifos or triazophos. In some experiments treatments significantly improved plant growth or yield, or both. Granules of carbofuran or phorate also reduced larval infestations and damage, but both thiofanox granules and dimethoate sprays were ineffective. Sprays of

Effect of a turnip rape (Brassica rapa) trap crop on stem-mining pests and their parasitoids in winter oilseed rape (Brassica napus)

“…Adult C. pallidactylus were abundant in early April, thereafter declining throughout May and June (Figure 1a). This timing concurs with the few other studies on this pest in the UK, e.g., on winter oilseed rape , on seedlings of Trowse mustard (Brassica juncea) (Winfield, 1961) and on spring oilseed rape (Graham and Gould, 1980). Graham and Gould (1980) suggested that winter oilseed rape was not damaged by C. pallidactylus but since then, Ferguson et al (2003) have reported stem injury to winter rape by this pest.…”

“…The pest status and phenology of C. pallidactylus has been less studied in the UK than in continental Europe, although there are some observations of its incidence on both winter and spring (Winfield, 1961;Graham and Gould, 1980) oilseed rape. Adults migrate to winter oilseed rape in early spring (Bonnemaison, 1965;Walczak et al, 1998;Ferguson et al, 2003); in the UK, Ferguson et al (2003) caught them in flight traps from 20 April until 20 June.…”

“…They are all univoltine with three larval instars. The larvae feed inside the leaves (petioles and veins) and stem of the plant causing damage (Graham and Gould, 1980;Cox, 1998;Alford et al, 2003).…”

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

“…The economic threshold for the two weevil species varies among different regions and is based on their abundance and damage capabilities. 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 .…”

“…Stem weevils can cause significant yield losses, and some authors indicate that they can vary from 5% 9 to 32% or more, accounting for a loss of up to 800 kg ha −1 . Even cases with larval presence on 100% of plants are recorded …”