P.J. Gerard

Dependence of Sitona lepidus (Coleoptera: Curculionidae) larvae on abundance of white clover Rhizobium nodules

Sitona lepidus Gyllenhal (Coleoptera: Curculionidae) was first recognized in New Zealand pastures in the Waikato in March 1996 (Barratt et al., 1996). In Europe and North America, the species is considered to be a significant pest of clovers (Barratt et al., 1996 and references therein). However, white clover Trifolium repens L. (Fabaceae) is the key to profitability in New Zealand‘s pastoral industries, and the rate of spread and severity of clover damage experienced by farmers indicated that S. lepidus may become amongst the most serious pasture pest species in New Zealand. The only other Sitona species present in New Zealand is Sitona discoideus Gyllenhal (Barratt et al., 1996), a pest of lucerne, Medicago sativa L. (Fabaceae). All instars of this species damage root nodules (Allen, 1971) and the high degree of density-dependent mortality seen in Canterbury pastures is considered to arise amongst the neonate larvae during their establishment in the root nodules (Goldson et al., 1988). Observations by the author of S. lepidus larvae feeding on roots in glass-fronted display cases indicated that first instar larvae of this species fed on the fine roots of clover as well as root nodules. This paper reports the results of two experiments investigating the relationships between larval survival and development and the presence and abundance of root nodules.

Impact of clover root weevil Sitona lepidus (Coleoptera: Curculionidae) larvae on herbage yield and species composition in a ryegrass‐white clover sward

Abstract The effects of root herbivory at five densities of Sitona lepidus larvae (overall means between 4 and 333 larvae m‐2) were assessed over 2 years on newly established perennial ryegrass‐white clover swards in a small plot trial. Initial larval establishment in autumn 2003 was positively related to clover content in plots, and there was no significant impact on clover herbage yield in the first year. Nodule damage in winter 2003 increased with larval density, and results suggested an overcompensatory response in nodule production. A 34–35% reduction in clover yield between highest and lowest S. lepidus densities was recorded for both cultivars in the second year, with greatest losses in spring 2004. This coincided with reductions in clover root and stolon weights. Plant parasitic nematodes and grass grub larvae were most abundant in the plots with lowest weevil numbers. These results confirm field observations that S. lepidus is a major pest of pastures.

Potential effects of climate change on biological control systems: case studies from New Zealand

Biological control systems are integral to New Zealand’s success as a nation reliant on exporting quality agricultural, forestry and horticultural products. The likely impacts of climate change projections to 2090 on one weed and four invertebrate management systems in differing production sectors were investigated, and it was concluded that most natural enemies will track the changing distributions of their hosts. The key climate change challenges identified were: disparities in natural enemy capability to change distribution, lack of frosts leading to emergence of new pests and additional pest generations, non-target impacts from range and temperature changes, increased disruptions caused by extreme weather events, disruption of host-natural enemy synchrony, and insufficient genetic diversity to allow evolutionary adaptation. Five classical biological control systems based on the introduced species Longitarsus jacobaeae, Cotesia kazak, Aphelinus mali, Microctonus aethiopoides and Microctonus hyperodae are discussed in more detail.

Antifeedant and insecticidal activity of compounds from Pseudowintera colorata (Winteraceae) on the webbing clothes moth, Tineola bisselliella (Lepidoptera: Tineidae) and the Australian carpet beetle, Anthrenocerus australis (Coleoptera: Dermestidae)

Extracts of the leaves of the New Zealand native tree Pseudowintera colorata (Raoul) showed insecticidal and antifeedant activity against the webbing clothes moth, Tineola bisselliella (Hummel), and antifeedant activity against the Australian carpet beetle, Anthrenocerus australis (Hope). Assay-directed fractionation showed that two sesquiterpene dialdehydes, polygodial and 9-deoxymuzigadial, were responsible for these activities. Both compounds had similar antifeedant and insecticidal activity at rates from 3 to 0.4 mg/g wool in bioassays.

Synthesis and Biological Activity of Allosamidin and Allosamidin Analogues

The chitinase inhibitor/insect ecdysis inhibitor allosamidin and eight allosamidin analogues have been synthesised from simple carbohydrate starting materials. Allosamidin was assayed against Tineola bisselliella (Hummel) larvae and all nine compounds were examined for their effects on the development of larvae of Lucilia cuprina (Wiedemann). High larval mortality compared to controls resulted when T. bisselliella and L. cuprina larva were exposed to allosamidin. The (1→3) linked regioisomer, the dimeric analogue and the gluco-configurated dimeric analogue of allosamidin all showed high activity against L. cuprina larvae. The regioisomer, the (1→3) linked isomer and its dimeric analogue, as well as the monomer allosamizoline and its regioisomer, were inactive. These new in-vivo results are consistent with known in-vitro insect chitinase inhibition data, in that greatest larval mortality was exhibited by the best inhibitors.

The positive contribution of invertebrates to sustainable agriculture and food security

This study focuses on three main groups of organisms: soil invertebrates, biological control agents (BCAs) and pollinators. These groups play key roles in agricultural systems, and have the potential to be used, moved or manipulated for the benefit of agriculture. Soil invertebrates are a key component of agricultural landscapes. They participate in essential soil processes that maintain healthy productive soils in the face of changing environmental conditions. Reducing the diversity of a community of soil invertebrates reduces its beneficial functions and services, with drastic ecological effects such as long-term deterioration of soil fertility and agricultural productive capacity. The introduction of a keystone species may have detrimental or beneficial effects depending on the context. The interaction between soil invertebrates and soil microorganisms is critical: the activities of soil invertebrates regulate microbial activity in soils, and micro-organisms enter into intimate relationships with soil invertebrates to help them degrade highly complex compounds such as cellulose. Different groups of invertebrates provide biological control of crop pests. In many situations, they form the basis of, and tools for, the integrated pest management (IPM) approach. Given that the losses caused by pre- and post-harvest pests can be very substantial, the potential benefits of using invertebrates as BCAs are vast, but as yet only partially tapped. The potential for soil invertebrates to assist in this function is still largely unknown. Pollination services by animals, especially by insects, are among the most widespread and important processes that structure ecological communities in both natural and agricultural landscapes. An estimated 60–90% of the world’s flowering plants – including a range of economically important species – depend on insects for pollination. Crop pollination used to be (and often still is) provided by wild pollinators spilling over from natural and semi-natural habitats close to crop fields. This service has generally been free and therefore has received little attention in agricultural management. If wild pollinators are lacking or additional pollination is required, as is the case in many intensive agricultural production systems, farmers in some developed countries can buy or rent managed honeybees or sometimes other species (e.g. bumblebees, alfalfa leafcutter bees and alkali bees). Both options – i.e. use of wild species and managed bees – have recently come under pressure, a development that is sometimes referred to as the ‘pollination crisis’. Of the interactions and overlaps between these key groups, that between soil invertebrates and BCAs is the most important, and further research is needed to evaluate the scope and impact of manipulation of the soil ecosystem to conserve or encourage beneficial BCAs.

Insect Antifeedant Sesquiterpene Acetals from the Liverwort Lepidolaena clavigera. 2. Structures, Artifacts, and Activity

Clavigerin A ( 1) was isolated from the New Zealand liverwort Lepidolaena clavigera and shown to be a polyoxygenated bergamotane sesquiterpene with an unusual ring system. L. clavigera shows infraspecific variation, since 1 was the only clavigerin detected in a North Island collection, whereas the previously reported clavigerins B ( 2) and C ( 3) were found in South Island collections with no sign of 1. Three new clavigerins, 4- 6, were identified, but these are artifacts formed by alcoholysis of the acetoxy acetal group of the clavigerins 2 and 3, with either the extraction solvent ethanol or the RP column eluent methanol. The insect antifeedant and cytotoxic activities of these compounds are reported, and it is proposed that they act as hidden 1,4-dicarbonyl compounds.

Insect antifeedant sesquiterpene acetals from the liverwort Lepidolaena clavigera

Two new oxygenated bergamotane derivatives, clavigerins B and C, were responsible for the insect antifeedant activity of an extract from the New Zealand liverwort Lepidolaena clavigera.

The implications of climate change for positive contributions of invertebrates to world agriculture

This review is based in part on a report that the authors prepared for the Commission on Genetic Resources for Agriculture (CGRFA), at the Food and Agriculture Organization of the United Nations (FAO), Rome, on climate change and invertebrate genetic resources for food and agriculture [277]. We thank Kim-Anh Tempelman and colleagues at the CGRFA for their interest, support and encouragement in preparing that report. We also thank Peter S. Baker (CABI), John Kean (AgResearch Ltd, New Zealand), Graham Walker (The New Zealand Institute for Plant & Food Research Limited), and Craig Phillips (AgResearch Ltd, New Zealand), who contributed Case Studies as indicated; Joop van Lenteren (Wageningen University, The Netherlands), Peter Baker and several anonymous scientists of the CGRFA and FAO who reviewed parts of a draft of the report from which this review was derived; and Rebecca J Murphy (UK) and Dafydd Pilling (FAO) for editorial inputs to that report.

Activity of extracts and compounds from New Zealand gymnosperms against larvae of Lucilia cuprina (Diptera: Calliphoridae)

Abstract A modified serum‐based bioassay was used to screen plant extracts and assess compound activity against newly hatched larvae of the Australian sheep blowfly Lucilia cuprina. Larval instar mortality and physical appearance were recorded after exposure for 24 h to the treatments. Extracts from New Zealand gymnosperms shown to have activity against L. cuprina larvae were: Podocarpus totara; P. acuteafolius; Dacrycarpus dacrydioides; Halocarpus bidwillii; H. biformis; H. kirkii; Lagarostrobos colensoi; Lepidothamnus intermedius; L. laxifolius; Phyllocladus tricho‐manoides; P. glaucus, and Agathis australis. The phytoecdysones 20‐hydroxyecdysone, 5,20‐dihydroxyecdysone, and ponasterone A inhibited larval moulting. Dyshomoerythrine, dacrysterone, and nagilactone C were insecticidal, with the latter also retarding growth at sublethal rates.