Effect of orchard management, neighbouring land-use and shelterbelt tree composition on the parasitism of pest leafroller (Lepidoptera: Tortricidae) larvae in kiwifruit orchard shelterbelts

The parasitoid communities in organic and integrated pest management (IPM) kiwifruit orchards have previously been found to differ significantly, but we do not know if this affects the quality or quantity of biocontrol services. We compared parasitism of two leafroller (Lepidoptera: Tortricidae) pest species, Ctenopseustis obliquana (Walker) and Cnephasia jactatana (Walker), in the two types of orchard. Within each orchard, we focussed on a large shelterbelt between the kiwifruit vines and an alternative land-use to also investigate whether the shelterbelts and neighbouring habitat were a source of pests or beneficial insects for these orchards. Sentinel larvae were used to determine both parasitoid identity and parasitism rate each month during the kiwifruit growing seasons in 2013/14 (16 orchards) and 2014/15 (12 orchards). The numbers of Tortricidae and parasitoids in the shelterbelt on each orchard in each month was also assessed in 2014/15. Four parasitoid species emerged from the sentinel larvae, although average parasitism rates were very low (1-3%). There were no detectable effects of orchard management, shelterbelt type or neighbouring land-use on parasitism rates. Parasitoid numbers were low in all orchards in 2014/15, although more parasitoids were collected from the IPM orchards than the organic ones. This may have been in response to the increasing numbers of Tortricidae in the shelterbelts on the IPM orchards during the season, a trend that was not observed in the organic orchards. Both shelterbelt composition and neighbouring land-use were found to affect total combined counts of Tortricidae and parasitoids, with higher counts in shelterbelts composed of Cryptomeria japonica and where adjacent land contained native bush or tree-based scrub. Each may therefore be a source of both taxa for the orchards. Modifications to the shelterbelts that increase parastoids but not Tortricidae are needed.