Field Parasitism of Nontarget Weevil Species (Coleoptera: Curculionidae) by the Introduced Biological Control Agent <I>Microctonus aethiopoides</I> Loan (Hymenoptera: Braconidae) over an Altitude Gradient

Abstract

The parasitoid, Microctonus aethiopoides Loan (Hymenoptera: Braconidae) was introduced into New Zealand in 1982 to control the alfalfa pest, Sitona discoideus Gyllenhal (Coleoptera: Curculionidae). Studies have shown that a number of nontarget weevil species are attacked in the field by this parasitoid. A field study was carried out to investigate nontarget parasitism by M. aethiopoides over an altitudinal sequence from the target host habitat (alfalfa) into native grassland. Three locations were selected for the study, and at each, the alfalfa growing in the valley floor was sampled annually for parasitism of the target pest that ranged between 17 and 78%. At progressively higher altitudes, three further grassland sites at each location were sampled monthly during spring to autumn for up to 6 yr. Weevil densities were estimated, species identified, and dissections carried out to determine reproductive status and parasitism. Almost 12,000 weevils were collected during the study, which were identified as 36 species in total from the three locations. Eight weevil species were found to be parasitized, including S. discoideus, the target host that was found at all sites. Parasitism of nontarget species was approximately 2% overall but varied with location, site, and season. Substantial nontarget parasitism was found at only one of the locations, with up to 24% parasitism of a native weevil, Nicaeana fraudator Broun (Coleoptera: Curculionidae), recorded. Another species, Irenimus egens (Broun) (Coleoptera: Curculionidae), was also found at this location at similar population densities but was attacked far less by M. aethiopoides. Results are discussed in relation to weevil phenology.

Parasitism of a Hawaiian Endemic Moth by Invasive and Purposely Introduced Hymenoptera Species

“…This is consistent with other studies that have shown that the same nontarget host was not affected equally at different habitats (Barratt et al 1997(Barratt et al , 2007Benson et al 2003;Follett at al. 2000b;Johnson et al 2005).The fact that densities of larvae, parasitism rates, and parasitoid guild varied among the three sites in the Ditch trail in Kokee State Park suggests that subtle ecological differences inßuence the occurrence of both the moth and its parasitoids signiÞcantly.…”

Biodiversity of indigenous tussock grassland sites in Otago, Canterbury and the Central North Island of New Zealand VI. Coleoptera biodiversity, community structure, exotic species invasion, and the effect of disturbance by agricultural development

“…5 226 BIP Barratt et al 2007), showed that when treatments were combined for all sites, cultivated treatments were more distant from a log-normal distribution compared with the native and oversown treatments (Fig. 6a).…”

Risk Analysis Frameworks Used in Biological Control and Introduction of a Novel Bayesian Network Tool

“…The introduction in 1982 of a hymenopteran endoparasitoid, M. aethiopoides (Braconidae: Euphorinae), successfully reduced S. discoideus populations providing benefits to farmers (Goldson et al., 1993). Concerns arose when it was discovered that 19 species of nontarget weevils were attacked in the field, 14 of which are native species (Barratt & Johnstone, 2001; Barratt et al., 2007, 2010). The nontarget parasitism associated with the introduction of M. aethiopoides in New Zealand provides an interesting case of a BCA initially expected to establish only in the receiving environment (lucerne crops and pastures) but which has now established populations in natural ecosystems (mainly mid‐altitude native tussock grasslands that are habitats for native weevil species).…”