Long range forecasts of the numbers of Helicoverpa punctigera and H-armigera (Lepidoptera : Noctuidae) in Australia using the Southern Oscillation Index and the Sea Surface Temperature

The use of long-term forecasts of pest pressure is central to better pest management. We relate the Southern Oscillation Index (SOI) and the Sea Surface Temperature (SST) to long-term light-trap catches of the two key moth pests of Australian agriculture, Helicoverpa punctigera (Wallengren) and H. armigera (Hubner), at Narrabri, New South Wales over 11 years, and for H. punctigera only at Turretfield, South Australia over 22 years. At Narrabri, the size of the first spring generation of both species was significantly correlated with the SOI in certain months, sometimes up to 15 months before the date of trapping. Differences in the SOI and SST between significant months were used to build composite variables in multiple regressions which gave fitted values of the trap catches to less than 25% of the observed values. The regressions suggested that useful forecasts of both species could be made 6-15 months ahead. The influence of the two weather variables on trap catches of H. punctigera at Turretfield were not as strong as at Narrabri, probably because the SOI was not as strongly related to rainfall in southern Australia as it is in eastern Australia. The best fits were again given by multiple regressions with SOI plus SST variables, to within 40% of the observed values. The reliability of both variables as predictors of moth numbers may be limited by the lack of stability in the SOI-rainfall correlation over the historical record. As no other data set is available to test the regressions, they can only be tested by future use. The use of long-term forecasts in pest management is discussed, and preliminary analyses of other long sets of insect numbers suggest that the Southern Oscillation Index may be a useful predictor of insect numbers in other parts of the world.

Toxicity of biorational insecticides to Helicoverpa spp. (Lepidoptera : Noctuidae) and predators in cotton field

Field trials on upland cotton (Gossypium hirstum L.) during its reproductive phase were used to assess the toxicity of several biorational pesticides and chemicals to Helicoverpa armigera (Hubner) and H. puntigera Wallengren, as well as major predators at Dalby, Queensland, Australia. Moderate rate-dependent control was obtained in plots treated with neem (Azadirachta indica A. Juss) seed extract-azadirachtin (Aza) at rates of 30, 60 and 90 g/ha. Plots treated with Talstar EC (bifenthrin) applications achieved the best results, followed by treatment with alternation of chemicals (methomyl, bifenthrin, thiodicarb and endosulfan) and biorational insecticides (neem oil, azadirachtin and Bacillus thuringiensis kurstaki var. Berliner). Predators, including lady beetles, lacewings, spiders and predatory bugs, were insensitive to Aza, tooseendanin (Tsdn) and BT applications. In contrast, chemicals were very destructive of predators. All treatments provided some protection from infestation of H. armigera and H. puntigera. The effect of Aza on Helicoverpa spp. was reflected in a relatively higher yield of seed cotton harvested from Aza-treated plots compared with the control, but chemical control achieved significantly higher yields than any other treatment.

Survival and development of Helicoverpa armigera (Hubner) (Lepidoptera : Noctuidae) on neem (Azadirachta indica A. Juss) leaves

The survival, development and feeding responses of Helicoverpa armigera (Hubner) on neem (Azadirachta indica A. Juss) leaflets were evaluated under choice and no-choice conditions. Neem leaflets provided to starving fourth-instar larvae were chewed, but larvae expectorated most of the material. The weight of surviving larvae decreased and no fourth instars completed development on neem leaflets alone. Larvae resumed feeding when transferred to cotton leaves after 5 days of feeding on neem leaflets. Fourth instars strongly discriminated between neem leaflets and cotton leaves when offered a choice. Early sixth instars decreased in weight and had delayed development when feet only on neem leaflets. Mure than one-half lived for more than 2 weeks and some completed development to adults. Neem is an unacceptable non-host plant species for H. armigera.

Foraging and vein-cutting behaviour of Euploea core corinna (W.S. Macleay) (Lepidoptera : Nymphalidae) caterpillars feeding on latex-bearing leaves

Caterpillars of Euploea core corinna (W. S. Macleay) sever leaf veins prior to feeding on their latex-bearing host plants, which restricts the flow of latex at feeding sites. The severing of leaf veins by insects feeding on latex-bearing plants is commonly referred to as 'sabotaging' and is thought to be an evolved response by the insect to counter the negative effects of feeding on latex-rich leaves. Sabotaging behaviour is described for all instars of E. core corinna, with particular attention given to neonates. Vein cutting by neonate E. core corinna caterpillars can occur within 2 h of hatching, with most caterpillars establishing feeding sites within 10 h. Commonly, first instars cut an are-shaped row of leaf side-veins parallel to the leaf margin, but they may also cut the leaf mid-rib in a fashion similar to older instar larvae. From a sample of 50 E. core corinna larvae, representing all instars, we found that the diameters of the veins cut by caterpillars are closely correlated to larval head width (r=0.90). Through manipulative experiments, we demonstrate for the first time that sabotaging behaviour in neonate caterpillars imposes no detectable short-term physiological costs on those caterpillars.

Residues of zeta-cypermethrin in bovine tissues and milk following pour-on and spray application

The depletion of zeta-cypermethrin residues in bovine tissues and milk was studied. Beef cattle were treated three times at 3-week intervals with 1 ml 10 kg(-1) body weight of a 25 g litre(-1) or 50 g litre(-1) pour-on formulation (2.5 and 5.0 mg zeta-cypermethrin kg(-1) body weight) or 100 mg kg(-1) spray to simulate a likely worst-case treatment regime. Friesian and Jersey dairy cows were treated once with 2.5 mg zeta-cypermethrin kg(-1) in a pour-on formulation. Muscle, liver and kidney residue concentrations were generally less than the limit of detection (LOD = 0.01 mg kg(-1)). Residues in renal-fat and back-fat samples from animals treated with 2.5 mg kg(-1) all exceeded the limit of quantitation (LOQ = 0.05 mg kg(-1)), peaking at 10 days after treatment. Only two of five kidney fat samples were above the LOQ after 34 days, but none of the back-fat samples exceeded the LOQ at 28 days after treatment. Following spray treatments, fat residues were detectable in some animals but were below the LOQ at all sampling intervals. Zeta-cypermethrin was quantifiable (LOQ = 0.01 mg kg(-1)) in only one whole-milk sample from the Friesian cows (0.015 mg kg(-1), 2 days after treatment). In whole milk from Jersey cows, the mean concentration of zeta-cypermethrin peaked 1 day after treatment, at 0.015 mg kg(-1), and the highest individual sample concentration was 0.025 mg kg(-1) at 3 days after treatment. Residues in milk were not quantifiable beginning 4 days after treatment. The mean concentrations of zeta-cypermethrin in milk fat from Friesian and Jersey cows peaked two days after treatment at 0.197 mg kg(-1) and 0.377 mg kg(-1), respectively, and the highest individual sample concentrations were 2 days after treatment at 0.47 mg kg(-1) and 0.98 mg kg(-1), respectively. (C) 2001 Society of Chemical Industry.

Ecology and behavior of first instar larval Lepidoptera

Neonate Lepidoptera are confronted with the daunting task of establishing themselves on a food plant. The factors relevant to this process need to be considered at spatial and temporal scales relevant to the larva and not the investigator. Neonates have to cope with an array of plant surface characters as well as internal characters once the integument is ruptured. These characters, as well as microclimatic conditions, vary within and between plant modules and interact with larval feeding requirements, strongly affecting movement behavior, which may be extensive even for such small organisms. In addition to these factors, there is an array of predators, pathogens, and parasitoids with which first instars must contend. Not surprisingly, mortality in neonates is high but can vary widely. Experimental and manipulative studies, as well as detailed observations of the animal, are vital if the subtle interaction of factors responsible for this high and variable mortality are to be understood. These studies are essential for an understanding of theories linking female oviposition behavior with larval survival, plant defense theory, and population dynamics, as well as modern crop resistance breeding programs.

A coiled-coil region of an insect immune suppressor protein is involved in binding and uptake by hemocytes

Polydnaviruses are associated with certain parasitoid wasps and are introduced into the body cavity of the host caterpillar during oviposition. Some of the viral genes are expressed in host tissues and corresponding proteins are secreted into the hemocoel causing suppression of the host immune system. The Cotesia rubecula polydnavirus gene product, CrV1, effectively inactivates hemocytes by mediating cytoskeleton break-down. A precondition for the CrV1 function is the incorporation of the extracellular protein by hemocytes. Here, we show that a coiled-coil domain containing a putative leucine zipper is required for CrV1 function, since removal of this domain abolishes binding and uptake of the CrV1 protein by hemocytes. (C) 2002 Elsevier Science Ltd. All rights reserved.

Sequence analysis and expression of a virus-like particle protein,VLP2, from the parasitic wasp Venturia canescens

Endoparasitoid wasps produce maternal protein secretions, which are transported into the body of insect hosts at oviposition to regulate host physiology for successful development of their offspring. Venturia canescens calyx fluid contains so-called virus-like particles (VLPs) that are essential for immune evasion of the developing parasitoid inside the host. VLPs consist of four major proteins. In this paper, we describe the isolation and molecular cloning of a gene (vlp2) that is a constituent of VLPs and discuss its possible role in VLP structure and function.

Does habitat modification affect oviposition by the salt marsh mosquito, Ochlerotatus vigilax (Skuse) (Diptera : Culicidae)?

Studies were conducted at sites in south-cast Queensland, Australia, to investigate the effect of habitat modification for mosquito control on the distribution of eggshells of the salt marsh mosquito, Ochlerotatus vigilax (Skuse). Modifications were mainly tunnelling, but an Open Marsh Water Management (OMWM) site and a grid-ditched site were also included. There were two separate experimental designs: one was data collected Before and After (BA) modification and the other was for other sites with a Treatment and Control (TC) experimental design. For the BA data, there were significant reductions in eggshells after modification. Eggshells were generally fewer after modification in areas which were close to unrestricted tidal flushing. A sandy substrate and vegetation changes which resulted in reduced Sporobolus virginicus or mixed Sporobolus and Sarcocornia quinqueflora also contributed to the effect. In the TC experiment, there was no effect of modification at the tunnelled site, eggshells were fewer at the OMWM site, but there were more eggshells at the grid-ditched site. There was some general indication that recent oviposition activity was reduced in sites that had been modified, evidenced by a relatively small proportion of young (dark coloured) eggshells.

Baseline laboratory bioassay data for spinosad against populations of Australian sheep blowfly, Lucilia cuprina (Wiedemann) (Diptera : Calliphoridae)

Spinosad was an effective larvicide against the Australian sheep blowfly, Lucilia cuprina. A survey of 41 field populations indicated no cross-resistance to spinosad from existing organophosphate resistance. The data presented serve as baseline data for future resistance surveys.

Isolation and characterization of a neprilysin-like protein from Venturia canescens virus-like particles

Maternal protein secretions from endoparasitoid wasps are evolutionary adaptations to regulate host physiology as part of an extended wasp phenotype. Virus-like particles (VLPs) produced in the calyx region of Venturia canescens wasps are involved in immune evasion of the developing parasitoid inside the host. In contrast to polydnaviruses (PDVs), VcVLPs are devoid of any nucleic acids. To understand the role of these particles in the regulation of host physiology and phylogenetic relationship between VLPs and PDVs, it is essential to identify particle proteins. In this paper, we describe the isolation and molecular cloning of a neprilysin-like gene (VcNEP) coding for a 94 kDa VcVLP protein and discuss its possible role in host regulation.

New status, species, distribution records and phylogeny for Australian mandibulate Chironomidae (Diptera)

All life-history stages of the Australian Podonominae (Chironomidae) genus Archaeochlus Brundin are revised, providing evidence for recognition of a separate clade, named here as Austrochlus Cranston. Based on molecular and morphological evidence, the clade contains two additional species: Austrochlus parabrundini Cranston, Edward and Cook sp. n. is described from Western Australia where its granite outcrop seepage habitat and geographical range is almost identical to that of the type species Austrochlus brundini Cranston, Edward and Colless (n. comb); Austrochlus centralaustralis Cranston, Edward and Cook sp. n. is described from ephemeral seepage/flows in the MacDonnell and James Ranges of central Australia. Molecular studies reported here confirm species distinctions, relationships to African taxa, and basal relationships within the Chironomidae. Modelled distributions provide evidence for range restriction by seasonal rainfall patterns.

Intragenomic variation in ITS2 rDNA in the louse of humans, Pediculus humanus: ITS2 is not a suitable marker for population studies in this species

The two internal transcribed spacers (ITS) of ribosomal DNA are often used as markers of populations of insects. We studied the ITS2 of the head lice and body lice of humans, to determine whether this gene is a suitable marker of populations of these insects. ITS2 sequences were amplified by PCR from lice from four different countries: Australia, China, Japan and the USA. Direct cycle-sequencing of some of these PCR products gave equivocal nucleotide chromatograms. This indicated that some lice had more than one ITS2 sequence, so we cloned PCR products from these lice. Temperature gradient gel electrophoresis (TGGE) revealed that 50 of the 67 clones we screened had different nucleotide sequences. All lice had several ITS2 types, including those with unequivocal chromatograms. A phylogenetic tree of 15 different ITS2 sequences showed that the sequences from individual lice were not monophyletic. We conclude that the ITS2 is not a useful marker of populations for Pediculus humanus.

Isolation and characterization of a novel venom protein from an endoparasitoid, Cotesia rubecula (Hym : Braconidae)

Insects are important vectors of diseases with remarkable immune defense capabilities. Hymenopteran endoparasitoids are adapted to overcome the host defense system and, therefore, are useful sources of immune-suppressing proteins. Not much is known about venom proteins in endoparasitoids, especially those that have a functional relationship with polydnaviruses (PDVs). Here, we describe the isolation and characterization of a small venom protein (Vn4.6) from an endoparositoid, Cotesia rubecula, which interferes with the activation of the host hemolymph prophenoloxidose. The coding region for Vn4.6 is located upstream in the opposite direction of a gene coding for a C rubecula PDV-protein (Crp32). Arch. Insect Biochem. Physiol. 53:92-100, 2003. (C) 2003 Wiley-Liss, Inc.

Virus or not? Phylogenetics of polydnaviruses and their wasp carriers

Our current, still limited, understanding of the comparative biology and evolution of polydnaviruses (PDVs) is reviewed, especially in the context of the possible origins of these parasitoid viruses and of their coevolution with carrier wasps. A hypothetical scenario of evolution of PDVs from ascovirus (or ascovirus-like) ancestors is presented, with examples of apparent extant transitional forms. PDVs appear, in the case of bracoviruses, to show phylogenetic relationships that mirror those of their wasp carriers: with ichno-viruses, the picture is less clear. Ongoing sequencing studies of entire PDV genomes from diverse wasp species are likely to greatly contribute to our understanding of PDV evolution. (C) 2003 Elsevier Science Ltd. All rights reserved.