Effect of buckwheat (Fagopyrum esculentum) on the abundance and efficacy of the leafroller parasitoid (Dolichogenidea tasmanica) in a Blenheim vineyard : A dissertation submitted in the partial fulfilment of the requirements for the degree of Bachelor of Science with Honours at Lincoln University

Abstract

Leafroller caterpillars (Lepidoptera: Tortricidae) are among the most economically important pests of New Zealand vineyards. Buckwheat, Fagopyrum esculentum Moench., was sown in a vineyard as a floral food resource for the parasitoid wasp Dolichogenidea tasmanica Cameron., a natural enemy of leafrollers. In this work, eight vine rows sown with a mid-row buckwheat strips were alternated with eight control strips (grassed) at Squire Estate vineyard, Blenheim. Two yellow 'Trappit' sticky traps per buckwheat and control row were used to catch D. tasmanica over four successive fortnightly trapping periods. Significantly higher numbers of D. tasmanica were captured in buckwheat compared with control rows. Yellow sticky traps were also used to determine D. tasmanica flight activity in a buckwheat row. Higher numbers of the parasitoid were caught at the height at which the buckwheat grew compared with traps placed at the height of the vine foliage; this difference was significant. An attempt was also made to assess leafroller and parasitoid cocoon numbers in buckwheat compared with control rows; however, the difference was not significant in both cases. The fact that D. tasmanica numbers were higher in buckwheat compared with control vine rows suggests that buckwheat may have potential as a conservation biological control tool to manage leafroller populations in New Zealand vineyards.