Abundance of leafrollers and their parasitoids on selected host plants in New Zealand

Abstract

The comparative abundance of orchard pest leafroller larvae was determined on eight host plants in the vicinity of pipfruit orchards. The greatest numbers occurred in Canterbury, followed by Nelson, Hawke's Bay, and Central Otago. In Hawke's Bay, leafroller larvae were Ctenopseustis H9800Q obliquana (41%), Planotortrix octo (15%), Epiphyas postvittana (16%), and Cnephasia jactatana (9%), and were most abundant on poplar, willow, and alder. In Nelson, leafrollers were E. postvittana (25%), Planotortrix excessana (23%), C. obliquana (23%), and C. herana (22%), found on willow, alder, clover, poplar, gorse, broom, dock, and plantain. In Canterbury, larvae were C. herana (51%), E. postvittana (34%), and P. octo (15%), mainly on broom, gorse, alder, poplar, dock, and clover. Leafrollers were very rare on host plants sampled in Central Otago, despite their pest status in horticulture. A total of 1460 larvae were reared to adults from the four regions, with 31% parasitism, of which two thirds were Dolichogenidea tasmanica (Braconidae). Parasitism varied significantly between leafroller larval host plants. Removal of leafroller host plants through mowing, pruning, careful shelter selection or other means could usefully reduce the leafroller pest density, and risk of incidence on crops.

The parasitoids of seed predators attacking snow tussocks,Chionochloaspp. (Poaceae)

“…Zealachertus tortriciphaga has been reared from five species of Tortricidae (Ctenopseustis obliquana, Planotortrix octo or excessana, Pyrgotis plagiatana and Atamacta alopecana), and one species in the Gracillariidae (Caloptilia elaeas) (Berry 1999). The first three listed tortricids are all polyphagous leafrollers of various native and exotic plants in New Zealand and known horticultural pests (Suckling et al 1998;Stevens et al 2002;Wearing et al 2003). This generalist wasp species may therefore feed on alternative hosts when M. calamogonus is uncommon or absent in low flowering years.…”

“…comm.). Another species in the same genus, D. tasmanica, is a known parasitoid of several native and introduced leafroller moths (Lepidoptera: Tortricidae) which, in their larval stage, are horticultural pests in New Zealand (Charles et al 1996;Suckling et al 1998;Burnip & Suckling 2001). Per cent parasitism by D. tasmanica ranges between 7.3 and 20.8% and emergence peaks in December and March, the early days of development of the first two instars of its host (Burnip & Suckling 2001).…”

Leafroller larval and adult phenology at two Canterbury, New Zealand, organic apple orchards

“…data). Previously we were unsure that an Australian parasitoid would be attracted to, or successfully develop in, endemic New Zealand taxa with which it had no past contact and therefore no opportunity for co-evolution (Suckling et al 1998). As graphs in Fig.…”

“…Numbers of adults caught in traps has been shown to be correlated with apple fruit damage when selective insecticides that do not kill adults are used (Bradley et al 1998). The general lack of correlation between catch and damage is probably also influenced by such factors as adult migration into the crop system from surrounding host plants {Dantharayana 1975;Tomkins 1984), the wide host range of leafrollers (Tomkins et al 1989;Dugdale & Crosby 1995), differences in larval phenology on different host plants (Thomas & Burnip 1993;Suckling et al 1998), and mortality factors reducing larval establishment. Despite these problems, considerable attempts have been made to understand and use pheromone trap catches in pest management, even though the larvae are the damaging life stage (Danthanarayana 1983;Charles et al 1996).…”

Recolonisation of an apple orchard by leafrollers (Lepidoptera: Tortricidae) following spraying

“…The Australian Epiphyas postvittana (Walker) (lightbrown apple moth) is the most widespread of these pests, while four native species in the genera Planotortrix (greenheaded leafrollers) and Ctenopseustis (brownheaded leafrollers) have more regional distributions (Foster et al 1991). Three of these species, E. postvittana, P. octo Dugdale and C. obliquana (Walker) are commonly found in Hawke's Bay (Charles et al 1996;Suckling et al 1998), the location of the current study. Leafrollers, especially E. postvittana, are highly polyphagous and include tree, shrub and ground cover species as hosts (Thomas 1989).…”