Comparative developmental biology of populations of three European and one North American Eubazus spp. (Hymenoptera: Braconidae), parasitoids of Pissodes spp. weevils (Coleoptera: Curculionidae)

Abstract

Observations were made on the developmental responses of the North American braconid species, Eubazus crassigaster, a parasitoid of the white pine weevil, Pissoles strobi, and three European congeneric species, £. semirugosus, E. robustus, and Eubazus sp. Several populations of Eubazus spp. were compared in their phenology in the laboratory and under natural conditions. When reared in the laboratory on non-diapausing Pissodes castaneus, mountain populations of £. semirugosus and £. robustus entered into an obligatory diapause in the host larva, whereas all the other populations tested developed continuously. Diapausing larvae continued their development only after having experienced at least three months at 2°C. Non-diapausing populations of Eubazus spp. significantly differed in the duration of pre-imaginal development, with £. semirugosus being the fastest developing species and £. robustus the slowest. Outdoor rearings of Eubazus spp. on P. castaneus showed that £. crassigaster, Eubazus sp. and the lowland biotype of £. semirugosus emerged in the year of oviposition if this occurred early enough to allow parasitoid development. In contrast, a majority of £. robustus individuals overwintered in the host larvae, regardless of the oviposition date. The diapausing, mountain biotype of £. semirugosus is considered as the most promising candidate for control of P. strobi in Canada, because it is likely to be better adapted to the life cycle of the target host than the other Eubazus spp., including the native £.crassigaster.

The role of fungus Beauveria bassiana in reducing the number of Pissodes castaneus (Col., Curculionidae) in young forests

“…So far, the papers published by Alauzet (1987Alauzet ( , 1990 and Kenis et al (1994Kenis et al ( , 1996Kenis et al ( , 2004 contain most information on the parasitoids of P. castaneus. Whilst little information concerns the pathogens of Pissodes weevils, mainly white pine weevil Pissodes strobi (Peck), which, especially in North America, is a dangerous pest of white pine (Pinus strobus L.) and Norway spruce [Picea abies (L.) H. Karst] (Alfaro et al 1995).…”

Discrimination of Eubazus (Hymenoptera, Braconidae) sibling species using geometric morphometrics analysis of wing venation

“…The work of Kenis et al . (1996) and Kenis & Mills (1998) exemplifies the problems posed by parasitoid taxonomy in biological control.…”

“…In this last paper, the authors also assigned the Nearctic specimens from Pissodes strobi , identified previously as E. crassigaster , to the newly restored species E. strigitergum (Cushman). To discriminate between these four sibling species, Kenis et al . (1996) and Kenis & Mills (1998) combined biological observations, isoenzyme analyses, cross‐mating experiments and classical morphometric analyses based on measurements of 43 morphological parameters.…”

Insecticidal activity of alpha-cypermethrin against small banded pine weevil Pissodes castaneus (Coleoptera: Curculionidae) in forest plantations and thickets

“…The death of larvae in treated trees was most likely caused by their contact with the insecticide, because there was no sign of infestation of larvae by parasitoids. The mortality of pest larvae developing in untreated trees was the lowest and caused by parasitoids from the Braconidae family, which are the main factor causing a reduction of P. castaneus populations (Kenis et al 1996(Kenis et al , 2004.…”