Susceptibilities of seven Brassicaceae species to infestation by the cabbage seedpod weevil (Coleoptera: Curculionidae)

Abstract

AbstractVarious genotypes of seven species of Brassicaceae (Brassica rapa L., B. napus L., B. juncea (L.) Czern., B. nigra (L.) Koch, B. tournefortii Gouan, Sinapis alba L., Crambe abyssinica Hochst. ex R.E. Fries, and B. napus × S. alba) were evaluated for susceptibility to infestation by the cabbage seedpod weevil, Ceutorhynchus obstrictus (Marsham). In the field, weevils were counted by excising and dissecting pod samples weekly for the presence of eggs, larvae, and larval exit holes. In the laboratory, excised pods from potted plants were exposed to gravid female weevils for 24 or 48 h and then the numbers of eggs and (or) feeding punctures were assessed. Differences in susceptibility of Brassicaceae species to the cabbage seedpod weevil were relatively consistent in both field and laboratory studies. Brassica rapa was the most susceptible. Intermediate susceptibility was observed for B. napus, B. napus × S. alba, B. tournefortii, and B. juncea, although the last species displayed some antixenotic resistance. Sinapis alba, B. nigra, and C. abyssinica were least susceptible. Pods of some species more frequently contained single, rather than multiple, larvae and this may have important implications for total yield loss, particularly in areas where opportunistic pests utilize weevil exit holes to gain access to seeds. New-generation adults fed on all Brassicaceae, and therefore all species may be susceptible to some yield loss. Canola growers in regions infested with C. obstrictus at high population densities can reduce losses by seeding S. alba, B. juncea, or a less susceptible genotype of B. napus.