Ceutorhynchus Obstrictus Marsham Research Articles

Managing cabbage seedpod weevils (Coleoptera: Curculionidae) in canola (Brassicaceae) – areLygus(Hemiptera: Miridae) affected?

AbstractCabbage seedpod weevil (Ceutorhynchus obstrictusMarsham; Coleoptera: Curculionidae) andLygusHahn (Hemiptera: Miridae) species are part of the late season insect pest complex of canola (BrassicaLinnaeus; Brassicacea) in the southern prairies of Canada. From 2010 to 2013, large strips in 73 commercial fields were studied in southern Alberta to validate action thresholds for cabbage seedpod weevil and assess the impact of insecticide spraying at the early flower stage for cabbage seedpod weevils on abundance ofLygusat the pod stage. Only fields planted in April accumulated the damaging populations of cabbage seedpod weevils, such that the application of an insecticide resulted in significant yield protection. The economic injury level for the cabbage seedpod weevil was calculated at 20 cabbage seedpod weevils per 10 sweeps, but an action threshold of 25–40 is recommended because sampling mainly occurs along the edge where cabbage seedpod weevils are initially concentrated. At the pod stage,Lyguswere lower in strips sprayed with insecticides at the early flower stage than in those not sprayed, but the differences were not statistically significant. Furthermore,Lyguswere generally below economically damaging levels in early seeded fields. Therefore, there is no benefit of spraying early seeded fields to attempt to preventLygusoutbreaks when cabbage seedpod weevils are below thresholds becauseLygusmay pose a risk only in fields planted later in the season.

Insect Pest Incidence and Injury to Herbicide‐Tolerant Canola in Western Canada

Genetically modified herbicide‐tolerant (HT) canola (Brassica napus L.) cultivars dominate the acreage planted to this oilseed crop in western Canada. We conducted a 3‐yr (2000–2002) field study near Lethbridge, AB, Canada to compare the incidence and damage of three key insect pests in Roundup Ready, Liberty Link (both HT), and Q2 (a conventional cultivar). Flea beetle (Phyllotreta cruciferae and P. striolata [Coleoptera, Chrysomelidae]) damage in 2000 ranged from 31 to 32% of foliage consumption at the cotyledon stage, which surpassed economic thresholds but was not related to cultivar. Cabbage seedpod weevil (Ceutorhynchus obstrictus Marsham [Coleoptera, Curculionidae]) damage to canola pods ranged from 58 to 70 holes per 100 pods in 2001, and lygus plant bugs (Lygus spp. [Heteroptera, Miridae]) at the early pod stage reached densities of >37 individuals per 10 sweeps in 2000 and 2002. For both insect pests, their damage or abundance was similar among the conventional and HT cultivars. We conclude that, in the short term, the insect pests common in southern Alberta do not exhibit a preference to invade and damage the transgenic herbicide canola cultivars commonly planted in the prairies.

On the misidentification of chalcid (Hymenoptera: Chalcidoidea) parasitoids of the cabbage seedpod weevil (Coleoptera: Curculionidae) in North America

AbstractPrevious identifications in North America ofTrichomalus perfectus(Walker, 1835) andMesopolobus morys(Walker, 1848) (Chalcidoidea: Pteromalidae), the principal chalcid parasitoids of the cabbage seedpod weevil (Ceutorhynchus obstrictusMarsham, 1802) in Europe, are shown to be misidentifications ofTrichomalus lucidus(Walker, 1835) andMesopolobus(Xenocrepis)moryoidessp. nov., respectively.Necremnus duplicatusGahan, 1941 (Chalcidoidea: Eulophidae) is synonymized formally underNecremnus tidius(Walker, 1839)syn. nov., confirming a previous, tentative synonymy. Both sexes ofN. tidius,M. moryoides, andT. lucidusare illustrated and compared with those of similar species using macrophotography and scanning electron microphotography. Hypotheses are offered to explain why the principal chalcid parasitoids of the cabbage seedpod weevil differ between North America and Europe and how the three treated species came to be in North America.