Effects of buckwheat flowers on leafroller (Lepidoptera: Tortricidae) parasitoids in a New Zealand vineyard

Abstract

1 The provision of floral resources in agricultural ecosystems can potentially enhance biological control of pests by providing nutrients to parasitoids. To test this, the effect of buckwheat Fagopyrum esculentum Moench flowers on leafroller parasitoids was investigated in a New Zealand vineyard. 2 Relative abundance of parasitoids was assessed with yellow sticky traps in buckwheat and control plots. Male Dolichogenidea tasmanica (Cameron) (Hymenoptera: Braconidae) were significantly more abundant in the presence of buckwheat. No significant result was found for female D. tasmanica or either sex of Glyptapanteles demeter (Wilkinson) (Hymenoptera: Braconidae), the other leafroller parasitoid caught. 3 The relative parasitism rate of leafrollers by D. tasmanica was assessed with a leafroller release and recover technique. No difference in parasitism was found between buckwheat and control plots. 4 The sex ratio (% males) of D. tasmanica emerging from recovered leafroller larvae was significantly lower in the presence of buckwheat than in control plots on one of the two release dates. Possible reasons for this increase in female production are discussed.

Evaluation of floral resources for enhancement of fitness of Gonatocerus ashmeadi, an egg parasitoid of the glassy-winged sharpshooter, Homalodisca vitripennis

“…Interestingly, L. maritima produced signiWcantly fewer male progeny over time suggesting a positive inXuence of this diet on daily female production as ovipositing females aged. A similar result was found for D. tasmanica, in which L. maritima Xowers increased the proportion of female oVspring compared with water in the laboratory (Berndt and Wratten, 2005), and a higher proportion of female oVspring were reared from sentinel hosts in F. esculentum Weld plots compared with control plots (Berndt et al, 2002). This illustrates the possibility of enhancing natural enemy eYciency through resource subsidies increasing female sex ratio (Kean et al, 2003).…”

Habitat manipulation to mitigate the impacts of invasive arthropod pests

“…Availability of flowering buckwheat (Fagopyrum esculentum Moench) (Scarratt 2005) and alyssum (Lobularia maritima (L.)) (Berndt and Wratten 2005) can increase fecundity and longevity and increase the proportion of female offspring of Dolichogenidea tasmanica Cameron, a key parasitoid of the leafrollers. Parasitism rates and leafroller densities have been shown to increase and decrease respectively in vineyards close to buckwheat and alyssum (Scarratt 2005;Irvin et al 2006), although 6 increased parasitism rates and/or decreased pest densities has not been achieved in all trials (Berndt et al 2002;Berndt et al 2006). Recent unpublished data indicate that leafroller densities can in some cases be reduced to below the economic threshold when flowering buckwheat is available.…”

Effect of food, light and host instar on the egg load of the synovigenic endoparasitoid Venturia canescens (Hymenoptera: Ichneumonidae)

“…Both laboratory and Weld cage studies demonstrate that parasitoids with access to sugar have greater longevity, fecundity, and more female biased sex ratios than starved parasitoids (Dyer and Landis 1996;Berndt et al 2002). Many parasitoids have been observed to feed on Xoral nectar in Welds (Jervis et al 1993), and crops with nearby Xowering vegetation have higher parasitism rates (Stephens et al 1998).…”