Erratum: External rostral characters for differentiation of sexes in the biological control agent Mecinus janthinus (Coleoptera: Curculionidae)

RésuméLe charançon perceur de tiges, Mecinus janthinus (Germar), est un agent de lutte biologique classique bien établi et prometteur pour le contrôle d'une mauvaise herbe exotique invasive, la linaire à feuilles larges (Linaria dalmatica (L.) Mill.) (Scrophulariaceae). Dans cet article, nous présentons des caractéristiques du rostre faciles à identifier, permettant la différenciation, à faible grossissement, des sexes de charançons perceurs de tiges vivants. Ces caractéristiques peuvent être utilisées par des travailleurs possédant une formation minimale afin d'identifier correctement le sexe des charançons. Ceci permettra donc une détermination rapide de la proportion des sexes des populations sur le terrain, améliorant ainsi les délais de capture, puis de lâchers.

External rostral characters for differentiation of sexes in the biological control agent Mecinus janthinus (Coleoptera: Curculionidae)

The stem-boring weevil, Mecinus janthinus (Germar), is a promising, well established classical biological control agent for the exotic invasive weed Dalmatian toadflax (Linaria dalmatica (L.) Mill.) (Scrophulariaceae). In this paper we present readily apparent rostral characters that can be used for sex differentiation of live stem-boring weevils at low magnification. These characters can be used by workers with little training to accurately sex weevils and can be used to rapidly determine sex ratios of field populations to improve timing of collection for redistribution.

Postrelease Evaluation of Mecinus janthinus Host Specificity, a Biological Control Agent for Invasive Toadflax (Linaria spp.)

Toadflax invasion into natural areas has prompted interest in weed management via biological control. The most promising biological control agent currently available for the control of Dalmatian toadflax is Mecinus janthinus, a stem-boring weevil that has been shown to significantly reduce toadflax populations. Some land managers, however, are reluctant to release approved weed biological control agents based on concerns about possible nontarget impacts. Few postrelease examinations of biocontrol impact and host specificity have been performed, despite the call for such information. This study examined the host specificity of Mecinus janthinus, postrelease, in relation to Colorado sites to provide information to managers about its relative safety as a weed biological control agent. This study employed three components: (1) greenhouse choice and no-choice experiments; (2) no-choice caged field experiments; and (3) release-site evaluation of nontarget use of native plant species where this weevil has been released and has established. Both greenhouse and field experiments failed to demonstrate nontarget use of native plant species by M. janthinus in the region where it was studied, even in no-choice starvation tests. We found no evidence of nontarget herbivory on native plants growing at toadflax sites where M. janthinus was well established. These results support the continued use of M. janthinus as a low-risk biological control agent for the management of toadflax in the Rocky Mountain Front Range.

Rapid differentiation of the sexes of adult Mecinus janthinus (Coleoptera: Curculionidae) based on external leg morphology

The stem-boring weevil, Mecinus janthinus Germar (Coleoptera: Curculionidae), was introduced from Europe to Canada in 1991 to control the noxious weeds Dalmatian toadflax, Linaria dalmatica (L.) P. Mill., and yellow toadflax, Linaria vulgaris P. Mill. (Scrophulariaceae) (De Clerck-Floate and Harris 2002; McClay and De Clerck-Floate 2002). Since its release, M. janthinus has established well on Dalmatian toadflax in British Columbia (BC) and, to a lesser extent, southern Alberta (De Clerck-Floate and Miller 2002), and it is beginning to show promise as a successful control agent against this weed (De Clerck-Floate and Harris 2002). However, it appears that M. janthinus has not thrived on yellow toadflax in Alberta (McClay and De Clerck-Floate 2002).