Factors Responsible for Changes in Leafroller (Lepidoptera: Tortricidae) Species Composition on Orchards and Vineyards 1974–2015, in Hawke’s Bay, New Zealand
2018
Lo, Peter L | Walker, James T S | Wearing, C Howard | Hedderley, Duncan I
Leafrollers are polyphagous pests whose larvae damage fruit and cause market access problems for fruit crops exported from New Zealand. Leafroller larvae and pupae were collected mainly from four fruit crops, but also from hedges, ornamental trees, and understory weeds in orchards and vineyards of Hawke’s Bay, a major fruit production region. Samples were collected from 1974 to 1977 and 1993 to 2015. This timespan was divided into periods that broadly coincided with broad-spectrum insecticide management, the transition to selective insecticides, and the full implementation of integrated fruit production (IFP) programs in apples, grapes, and stone fruit. Eight tortricid species were identified, but the accidentally introduced Epiphyas postvittana (Walker) (Lepidoptera: Tortricidae) and two native species, Ctenopseustis obliquana (Walker) and Planotortrix octo Dugdale, comprised 95% of the samples. The proportions of these three species varied according to interactions between four factors: pest management regime, collection period, property location, and host plant. In the 1970s under broad-spectrum insecticide programs, the native species dominated on all hosts. By the mid-late 1990s when IFP was introduced, all the main leafroller species were in decline. However, E. postvittana declined to a lesser extent than the two native species, and consequently, it became relatively more prominent. This change in species composition was delayed in two districts where localized cases of organophosphate insecticide resistance occurred in C. obliquana and P. octo. From 2000 onwards, E. postvittana was the dominant species in all districts and on all hosts, albeit with a much-reduced pest status, except on hedges and ornamental trees where C. obliquana prevailed.
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