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Sharon Downes - One of the best experts on this subject based on the ideXlab platform.
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Isolating, characterising and identifying a Cry1Ac resistance mutation in field populations of Helicoverpa punctigera
Scientific Reports, 2018Co-Authors: Tom Walsh, Juan Ferre, Bill James, Maissa Chakroun, Sharon DownesAbstract:Transgenic cotton expressing insecticidal proteins from Bacillus thuringiensis (Bt) has been grown in Australia for over 20 years and resistance remains the biggest threat. The native moth, Helicoverpa punctigera is a significant pest of cotton. A genotype causing resistance to Cry1Ac in H. punctigera was isolated from the field and a homozygous line established. The phenotype is recessive and homozygous individuals possess 113 fold resistance to Cry1Ac. Individuals that carry Cry1Ac resistance genes are rare in Australia with a frequency of 0.033 being detected in field populations. RNAseq, RT-PCR and DNA sequencing reveals a single nucleotide polymorphism at a splice site in the cadherin gene as the causal mutation, resulting in the partial transcription of the intron and a premature stop codon. Analysis of Cry1Ac binding to H. punctigera brush border membrane vesicles showed that it is unaffected by the disrupted cadherin gene. This suggests that the major Cry1Ac target is not cadherin but that this molecule plays a key role in resistance and therefore the mode of action. This work adds to our knowledge of resistance mechanisms in H. punctigera and the growing literature around the role of cadherin in the mode of action of Cry1 type Bt proteins.
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Toxicity and Cross-Resistance of Insecticides to Cry2Ab-Resistant and Cry2Ab-Susceptible Helicoverpa armigera and Helicoverpa punctigera (Lepidoptera: Noctuidae)
Journal of Economic Entomology, 2014Co-Authors: Lisa J. Bird, Sharon DownesAbstract:Since 2004-2005 cotton expressing Cry1Ac and Cry2Ab insecticidal proteins from the bacterium Bacillus thuringiensis has been commercially available in Australia to manage the target pests Helicoverpa armigera (Hubner) and Helicoverpa punctigera (Wallengren). In both target species, the frequency of alleles conferring resistance to Cry2Ab is unexpectedly high in field populations. A significant challenge for managing these pests would occur if resistance to Cry2Ab toxins inadvertently selected for resistance to other insecticides used to control them. Dose-response bioassays were performed to measure the toxicity of currently registered insecticide sprays on isogenic strains of Cry2Ab-resistant and Cry2Ab-susceptible H. armigera and H. punctigera. Within-species comparisons of Cry2Ab-resistant and Cry2Ab-susceptible strains of H. armigera and H. punctigera indicate no cross-resistance with pyrethroid insecticides. Additionally, Cry2Ab-resistant strains were not cross-resistant to the following selective insecticides: indoxacarb, chlorantraniliprole, and avermectins. In both H. armigera and H. punctigera, Cry2Ab-resistant colonies exhibited a small, but significant, degree of enhanced susceptibility in response to chlorpyrifos and methomyl. We report higher tolerance to conventional insecticides in H. armigera compared with H. punctigera. Our results indicate that there is no significant interplay between Cry2Ab resistance frequencies in H. armigera and H. punctigera and frequencies of resistance to a range of insecticide sprays currently registered for cotton. Therefore, we conclude that any increases in frequencies of the common Cry2Ab resistance phenotypes identified in Australian populations of Helicoverpa spp. are unlikely to increase resistance risk for the indoxacarb, chlorantraniliprole, or avermectin classes of insecticide.
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dual cry2ab and vip3a resistant strains of Helicoverpa armigera and Helicoverpa punctigera lepidoptera noctuidae testing linkage between loci and monitoring of allele frequencies
Journal of Economic Entomology, 2014Co-Authors: Tom Walsh, Sharon Downes, William James, Tracey Parker, J Gascoyne, Joel Armstrong, R J MahonAbstract:ABSTRACT Considerable attention has been given to delaying the evolution of insect resistance to toxins produced by transgenic crops. The major pests of cotton in Australia are the Lepidoptera Helicoverpa armigera (Hubner, 1805) and Helicoverpa punctigera (Wallengren), and the toxins deployed in current and imminent transgenic cotton varieties are Cry1Ac, Cry2Ab and Vip3A from Bacillus thuringiensis. In this study, lines that carry alleles conferring resistance to Cry2Ab and Vip3A were isolated using F2 tests. Extensive work on the Cry2Ab resistant lines, and preliminary work on the Vip3A resistant lines, suggested a single common resistance to each toxin in both species thereby justifying the use of more efficient F1 tests as the primary means for monitoring changes over time. A potential further efficiency could be gained by developing a single resistant line that carries both types of Bt resistance. Herein we report on work with both H. armigera and H. punctigera that tests whether dual Cry2Ab-Vip3A re...
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evolution ecology and management of resistance in Helicoverpa spp to bt cotton in australia
Journal of Invertebrate Pathology, 2012Co-Authors: Sharon Downes, R J MahonAbstract:Prior to the widespread adoption of two-gene Bt cotton (Bollgard II®) in Australia, the frequency of resistance alleles to one of the deployed proteins (Cry2Ab) was at least 0.001 in the pests targeted namely, Helicoverpa armigera and Helicoverpa punctigera. In the 7 years hence, there has been a statistically significant increase in the frequency of alleles conferring Cry2Ab resistance in field populations of H. punctigera. This paper reviews the history of deploying Bt cotton in Australia, the characteristics of the isolated Cry2Ab resistance that likely impact on resistance evolution, aspects of the efficacy of Bollgard IIχ, and the behavioural ecology of Helicoverpa spp. larvae as it pertains to resistance management. It also presents up-to-date frequencies of resistant alleles for H. punctigera and reviews the same information for H. armigera. This is followed by a discussion of current resistance management strategies. The consequences of the imminent release of a third generation product that utilizes the novel vegetative insecticidal protein Vip3A are then considered. The area planted to Bt-crops is anticipated to continue to rise worldwide and many biotechnical companies intend to add Vip3A to existing products; therefore the information reviewed herein for Australia is likely to be pertinent to other situations.
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characteristics of resistance to bacillus thuringiensis toxin cry2ab in a strain of Helicoverpa punctigera lepidoptera noctuidae isolated from a field population
Journal of Economic Entomology, 2010Co-Authors: Sharon Downes, Tracey Parker, R J MahonAbstract:ABSTRACT In 1996, the Australian cotton industry adopted Ingard that expresses the Bacillus thuringiensis (Bt) toxin gene cry1Ac and was planted at a cap of 30%. In 2004–2005, Bollgard II, which expresses cry1Ac and cry2Ab, replaced Ingard in Australia, and subsequently has made up >80% of the area planted to cotton, Gossypium hirsutum L. The Australian target species Helicoverpa armigera (Hubner) and Helicoverpa punctigera (Wallengren) are innately moderately tolerant to Bt toxins, but the absence of a history of insecticide resistance indicates that the latter species is less likely to develop resistance to Bt cotton. From 2002–2003 to 2006–2007, F2 screens were deployed to detect resistance to Cry1Ac or Cry2Ab in natural populations of H. punctigera. Alleles that conferred an advantage against Cry1Ac were not detected, but those that conferred resistance to Cry2Ab were present at a frequency of 0.0018 (n = 2,192 alleles). Importantly, the first isolation of Cry2Ab resistance in H. punctigera occurred b...
R J Mahon - One of the best experts on this subject based on the ideXlab platform.
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dual cry2ab and vip3a resistant strains of Helicoverpa armigera and Helicoverpa punctigera lepidoptera noctuidae testing linkage between loci and monitoring of allele frequencies
Journal of Economic Entomology, 2014Co-Authors: Tom Walsh, Sharon Downes, William James, Tracey Parker, J Gascoyne, Joel Armstrong, R J MahonAbstract:ABSTRACT Considerable attention has been given to delaying the evolution of insect resistance to toxins produced by transgenic crops. The major pests of cotton in Australia are the Lepidoptera Helicoverpa armigera (Hubner, 1805) and Helicoverpa punctigera (Wallengren), and the toxins deployed in current and imminent transgenic cotton varieties are Cry1Ac, Cry2Ab and Vip3A from Bacillus thuringiensis. In this study, lines that carry alleles conferring resistance to Cry2Ab and Vip3A were isolated using F2 tests. Extensive work on the Cry2Ab resistant lines, and preliminary work on the Vip3A resistant lines, suggested a single common resistance to each toxin in both species thereby justifying the use of more efficient F1 tests as the primary means for monitoring changes over time. A potential further efficiency could be gained by developing a single resistant line that carries both types of Bt resistance. Herein we report on work with both H. armigera and H. punctigera that tests whether dual Cry2Ab-Vip3A re...
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evolution ecology and management of resistance in Helicoverpa spp to bt cotton in australia
Journal of Invertebrate Pathology, 2012Co-Authors: Sharon Downes, R J MahonAbstract:Prior to the widespread adoption of two-gene Bt cotton (Bollgard II®) in Australia, the frequency of resistance alleles to one of the deployed proteins (Cry2Ab) was at least 0.001 in the pests targeted namely, Helicoverpa armigera and Helicoverpa punctigera. In the 7 years hence, there has been a statistically significant increase in the frequency of alleles conferring Cry2Ab resistance in field populations of H. punctigera. This paper reviews the history of deploying Bt cotton in Australia, the characteristics of the isolated Cry2Ab resistance that likely impact on resistance evolution, aspects of the efficacy of Bollgard IIχ, and the behavioural ecology of Helicoverpa spp. larvae as it pertains to resistance management. It also presents up-to-date frequencies of resistant alleles for H. punctigera and reviews the same information for H. armigera. This is followed by a discussion of current resistance management strategies. The consequences of the imminent release of a third generation product that utilizes the novel vegetative insecticidal protein Vip3A are then considered. The area planted to Bt-crops is anticipated to continue to rise worldwide and many biotechnical companies intend to add Vip3A to existing products; therefore the information reviewed herein for Australia is likely to be pertinent to other situations.
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characteristics of resistance to bacillus thuringiensis toxin cry2ab in a strain of Helicoverpa punctigera lepidoptera noctuidae isolated from a field population
Journal of Economic Entomology, 2010Co-Authors: Sharon Downes, Tracey Parker, R J MahonAbstract:ABSTRACT In 1996, the Australian cotton industry adopted Ingard that expresses the Bacillus thuringiensis (Bt) toxin gene cry1Ac and was planted at a cap of 30%. In 2004–2005, Bollgard II, which expresses cry1Ac and cry2Ab, replaced Ingard in Australia, and subsequently has made up >80% of the area planted to cotton, Gossypium hirsutum L. The Australian target species Helicoverpa armigera (Hubner) and Helicoverpa punctigera (Wallengren) are innately moderately tolerant to Bt toxins, but the absence of a history of insecticide resistance indicates that the latter species is less likely to develop resistance to Bt cotton. From 2002–2003 to 2006–2007, F2 screens were deployed to detect resistance to Cry1Ac or Cry2Ab in natural populations of H. punctigera. Alleles that conferred an advantage against Cry1Ac were not detected, but those that conferred resistance to Cry2Ab were present at a frequency of 0.0018 (n = 2,192 alleles). Importantly, the first isolation of Cry2Ab resistance in H. punctigera occurred b...
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incipient resistance of Helicoverpa punctigera to the cry2ab bt toxin in bollgard ii cotton
PLOS ONE, 2010Co-Authors: Sharon Downes, Tracey Parker, R J MahonAbstract:Combinations of dissimilar insecticidal proteins (“pyramids”) within transgenic plants are predicted to delay the evolution of pest resistance for significantly longer than crops expressing a single transgene. Field-evolved resistance to Bacillus thuringiensis (Bt) transgenic crops has been reported for first generation, single-toxin varieties and the Cry1 class of proteins. Our five year data set shows a significant exponential increase in the frequency of alleles conferring Cry2Ab resistance in Australian field populations of Helicoverpa punctigera since the adoption of a second generation, two-toxin Bt cotton expressing this insecticidal protein. Furthermore, the frequency of cry2Ab resistance alleles in populations from cropping areas is 8-fold higher than that found for populations from non-cropping regions. This report of field evolved resistance to a protein in a dual-toxin Bt-crop has precisely fulfilled the intended function of monitoring for resistance; namely, to provide an early warning of increases in frequencies that may lead to potential failures of the transgenic technology. Furthermore, it demonstrates that pyramids are not ‘bullet proof’ and that rapid evolution to Bt toxins in the Cry2 class is possible.
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binding site alteration is responsible for field isolated resistance to bacillus thuringiensis cry2a insecticidal proteins in two Helicoverpa species
PLOS ONE, 2010Co-Authors: Silvia Caccia, Carmen Sara Hernandezrodriguez, R J Mahon, Sharon Downes, William James, Nadine Bautsoens, Jeroen Van Rie, Juan FerreAbstract:Background Evolution of resistance by target pests is the main threat to the long-term efficacy of crops expressing Bacillus thuringiensis (Bt) insecticidal proteins. Cry2 proteins play a pivotal role in current Bt spray formulations and transgenic crops and they complement Cry1A proteins because of their different mode of action. Their presence is critical in the control of those lepidopteran species, such as Helicoverpa spp., which are not highly susceptible to Cry1A proteins. In Australia, a transgenic variety of cotton expressing Cry1Ac and Cry2Ab (Bollgard II) comprises at least 80% of the total cotton area. Prior to the widespread adoption of Bollgard II, the frequency of alleles conferring resistance to Cry2Ab in field populations of Helicoverpa armigera and Helicoverpa punctigera was significantly higher than anticipated. Colonies established from survivors of F2 screens against Cry2Ab are highly resistant to this toxin, but susceptible to Cry1Ac.
R J Akhurst - One of the best experts on this subject based on the ideXlab platform.
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variation in susceptibility of Helicoverpa armigera hubner and Helicoverpa punctigera wallengren lepidoptera noctuidae in australia to two bacillus thuringiensis toxins
Journal of Invertebrate Pathology, 2007Co-Authors: Lisa J. Bird, R J AkhurstAbstract:Abstract Intra-specific variation in susceptibility of Helicoverpa armigera (Hubner) and Helicoverpa punctigera (Wallengren) in Australia to the Cry1Ac and Cry2Ab δ-endotoxins from Bacillus thuringiensis (Berliner) (Bt) was determined to establish a baseline for monitoring changes that might occur with the use of Bt cotton. Strains of H. armigera and H. punctigera were established from populations collected primarily from commercial farms throughout the Australian cotton belts. Strains were evaluated for susceptibility using two bioassay methods (surface treatment and diet incorporation) by measuring the dose response for mortality (LC 50 ) and growth inhibition (IC 50 ). The variation in LC 50 among H. armigera ( n = 17 strains) and H. punctigera ( n = 12 strains) in response to Cry1Ac was 4.6- and 3.2-fold, respectively. The variation in LC 50 among H. armigera ( n = 19 strains) and H. punctigera ( n = 12 strains) to Cry2Ab was 6.6- and 3.5-fold, respectively. The range of Cry1Ac induced growth inhibition from the 3rd to 4th instar in H. armigera ( n = 15 strains) was 3.6-fold and in H. punctigera ( n = 13 strains) was 2.6-fold, while the range of Cry2Ab induced growth inhibition from neonate to 3rd instar in H. armigera ( n = 13 strains) was 4.3-fold and in H. punctigera ( n = 12 strains) was 6.1-fold. Variation in susceptibility was also evaluated for two age classes (neonates and 3rd instars) in laboratory strains of H. armigera and H. punctigera . Neonates of H. punctigera had the same or higher sensitivity to Bt than 3rd instars. Neonates of H. armigera were more sensitive to Cry2Ab than 3rd instars, while being less sensitive to Cry1Ac than 3rd instars. Differences in the two methods of bioassay used affected relative sensitivity of species to Bt toxins, highlighting the need to standardize bioassay protocols.
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toxicity of bacillus thuringiensis insecticidal proteins for Helicoverpa armigera and Helicoverpa punctigera lepidoptera noctuidae major pests of cotton
Journal of Invertebrate Pathology, 2002Co-Authors: Chunyan Liao, David G. Heckel, R J AkhurstAbstract:Abstract The susceptibilities of the major pests of cotton in Australia, Helicoverpa armigera and Helicoverpa punctigera, to some insecticidal proteins from Bacillus thuringiensis were tested by bioassay. A commercial formulation, DiPel, and individual purified insecticidal proteins were tested. H. armigera was consistently more tolerant to B. thuringiensis insecticidal proteins than was H. punctigera, although both were susceptible to only a limited range of these proteins. Only Cry1Ab, Cry1Ac, Cry2Aa, Cry2Ab, and Vip3A killed H. armigera at dosages that could be considered acceptable. There was no significant difference in the toxicities of Cry1Fa and Cry1Ac for H. punctigera but Cry1Fa had little toxicity for H. armigera. The five instars of H. armigera did not differ significantly in their susceptibility to DiPel on the basis of LC50. However, there were significant differences in the susceptibility to Cry1Ac and Cry2Aa of three strains of H. armigera. Bioassays conducted with Cry1Ac and Cry2Aa showed that there was a small but significant negative interaction between these δ-endotoxins.
Tom Walsh - One of the best experts on this subject based on the ideXlab platform.
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protein carbohydrate regulation in Helicoverpa amigera and h punctigera and how diet protein carbohydrate content affects insect susceptibility to bt toxins
Journal of Insect Physiology, 2018Co-Authors: Ashley E Tessnow, Tom Walsh, Spencer T Behmer, Gregory A SwordAbstract:Abstract Many animals, including insects, demonstrate a remarkable ability to regulate their intake of key macronutrients (e.g., soluble protein and digestible carbohydrates), which allows them to optimize fitness and performance. Additionally, regulating the intake of these two macronutrients enhances an animal’s ability to defend itself against pathogens, mitigate the effects of secondary plant metabolites, and decrease susceptibility to toxins. In this study, we first compared how Bt-resistant and -susceptible lines of Helicoverpa armigera and Helicoverpa punctigera regulate their intake of protein (p) and digestible carbohydrates (c). We found that there was no difference in the self-selected protein-carbohydrate intake target between resistant and susceptible genotypes of either species. We then explored the extent to which food protein-carbohydrate content altered the susceptibility of these species to three Bt toxins: Cry1Ac, Cry2Ab, and Vip3Aa. We found that H. armigera on diets that had protein-carbohydrate profiles that matched their self-selected protein-carbohydrate intake target were significantly less susceptible to Cry1Ac. In contrast, diet protein-carbohydrate content did not affect H. punctigera susceptibility to Cry1Ac. For both H. armigera and H. punctigera, susceptibility to Cry2Ab and Vip3Aa toxins did not change as a function of diet protein-carbohydrate profile. These results, when combined with earlier work on H. zea, suggest food protein-carbohydrate content can modify susceptibility to some Bt toxins, but not others. An increased understanding of how the nutritional environment can modify susceptibility to different Bt toxins could help improve pest management and resistance management practices.
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Isolating, characterising and identifying a Cry1Ac resistance mutation in field populations of Helicoverpa punctigera
Scientific Reports, 2018Co-Authors: Tom Walsh, Juan Ferre, Bill James, Maissa Chakroun, Sharon DownesAbstract:Transgenic cotton expressing insecticidal proteins from Bacillus thuringiensis (Bt) has been grown in Australia for over 20 years and resistance remains the biggest threat. The native moth, Helicoverpa punctigera is a significant pest of cotton. A genotype causing resistance to Cry1Ac in H. punctigera was isolated from the field and a homozygous line established. The phenotype is recessive and homozygous individuals possess 113 fold resistance to Cry1Ac. Individuals that carry Cry1Ac resistance genes are rare in Australia with a frequency of 0.033 being detected in field populations. RNAseq, RT-PCR and DNA sequencing reveals a single nucleotide polymorphism at a splice site in the cadherin gene as the causal mutation, resulting in the partial transcription of the intron and a premature stop codon. Analysis of Cry1Ac binding to H. punctigera brush border membrane vesicles showed that it is unaffected by the disrupted cadherin gene. This suggests that the major Cry1Ac target is not cadherin but that this molecule plays a key role in resistance and therefore the mode of action. This work adds to our knowledge of resistance mechanisms in H. punctigera and the growing literature around the role of cadherin in the mode of action of Cry1 type Bt proteins.
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crispr cas9 mediated genome editing of Helicoverpa armigera with mutations of an abc transporter gene haabca2 confers resistance to bacillus thuringiensis cry2a toxins
Insect Biochemistry and Molecular Biology, 2017Co-Authors: Jing Wang, Tom Walsh, Huidong Wang, Shaoyan Liu, Laipan Liu, Wee Tek Tay, Yihua YangAbstract:Abstract High levels of resistance to Bt toxin Cry2Ab have been identified to be genetically linked with loss of function mutations of an ABC transporter gene (ABCA2) in two lepidopteran insects, Helicoverpa armigera and Helicoverpa punctigera. To further confirm the causal relationship between the ABCA2 gene (HaABCA2) and Cry2Ab resistance in H. armigera, two HaABCA2 knockout strains were created from the susceptible SCD strain with the CRISPR/Cas9 genome editing system. One strain (SCD-A2KO1) is homozygous for a 2-bp deletion in exon 2 of HaABCA2 created by non-homologous end joining (NHEJ). The other strain (SCD-A2KO2) is homozygous for a 5-bp deletion in exon 18 of HaABCA2 made by homology-directed repair (HDR), which was produced to mimic the r2 resistance allele of a field-derived Cry2Ab-resistant strain from Australia. Both knockout strains obtained high levels of resistance to both Cry2Aa (>120-fold) and Cry2Ab (>100-fold) compared with the original SCD strain, but no or very limited resistance to Cry1Ac (
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complete mitochondrial genome of Helicoverpa zea lepidoptera noctuidae and expression profiles of mitochondrial encoded genes in early and late embryos
Journal of Insect Science, 2016Co-Authors: Omaththage P Perera, Tom Walsh, Randall G LuttrellAbstract:The mitochondrial genome (mitogenome) of the bollworm, Helicoverpa zea (Boddie), was assembled using paired-end nucleotide sequence reads generated with a next-generation sequencing platform. Assembly resulted in a mitogenome of 15,348 bp with greater than 17,000-fold average coverage. Organization of the H. zea mitogenome (gene order and orientation) was identical to other known lepidopteran mitogenome sequences. Compared with Helicoverpa armigera (Hubner) mitogenome, there were a few differences in the lengths of gaps between genes, but the lengths of nucleotide overlaps were essentially conserved between the two species. Nucleotide composition of the H. zea mitochondrial genome was very similar to those of the related species H. armigera and Helicoverpa punctigera Wallengren. Mapping of RNA-Seq reads obtained from 2-h eggs and 48-h embryos to protein coding genes (PCG) revealed that all H. zea PCGs were processed as single mature gene transcripts except for the bicistronic atp8 + atp6 transcript. A tRNA-like sequence predicted to form a hammer-head-like secondary structure that may play a role in transcription start and mitogenome replication was identified within the control region of the H. zea mitogenome. Similar structures were also found within the control regions of several other lepidopteran species. Expression analysis revealed significant differences in levels of expression of PCGs within each developmental stage, but the pattern of variation was similar in both developmental stages analyzed in this study. Mapping of RNA-Seq reads to PCG transcripts also identified transcription termination and polyadenylation sites that differed from the sites described in other lepidopteran species.
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dual cry2ab and vip3a resistant strains of Helicoverpa armigera and Helicoverpa punctigera lepidoptera noctuidae testing linkage between loci and monitoring of allele frequencies
Journal of Economic Entomology, 2014Co-Authors: Tom Walsh, Sharon Downes, William James, Tracey Parker, J Gascoyne, Joel Armstrong, R J MahonAbstract:ABSTRACT Considerable attention has been given to delaying the evolution of insect resistance to toxins produced by transgenic crops. The major pests of cotton in Australia are the Lepidoptera Helicoverpa armigera (Hubner, 1805) and Helicoverpa punctigera (Wallengren), and the toxins deployed in current and imminent transgenic cotton varieties are Cry1Ac, Cry2Ab and Vip3A from Bacillus thuringiensis. In this study, lines that carry alleles conferring resistance to Cry2Ab and Vip3A were isolated using F2 tests. Extensive work on the Cry2Ab resistant lines, and preliminary work on the Vip3A resistant lines, suggested a single common resistance to each toxin in both species thereby justifying the use of more efficient F1 tests as the primary means for monitoring changes over time. A potential further efficiency could be gained by developing a single resistant line that carries both types of Bt resistance. Herein we report on work with both H. armigera and H. punctigera that tests whether dual Cry2Ab-Vip3A re...
Myron P. Zalucki - One of the best experts on this subject based on the ideXlab platform.
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host plants and habitats of Helicoverpa punctigera and h armigera lepidoptera noctuidae in inland australia
Australian Journal of Entomology, 2019Co-Authors: Peter Gregg, Gary P. Fitt, Alice Del Socorro, Kris Le Mottee, Colin R Tann, Myron P. ZaluckiAbstract:For Helicoverpa punctigera (Wallengren), and to a lesser extent Helicoverpa armigera (Hubner), native host plants in non-cropping regions of inland Australia are believed to be contributors to populations which migrate in spring to infest cropping regions of south-east Australia, and southwestern Australia. Non-crop hosts were sampled using sweep nets in 71 survey trips in 19 years between 1987 and 2017 for larvae of H. punctigera and H. armigera, over about 2.4 million km in inland Australia. Of 1976 samples, H. punctigera larvae were present in 50.5%, distributed throughout the study area. Larvae were found on 106 host plant species in 24 families, including 61 new host records. H. armigera larvae were found on 33 plant species from eight families, including 14 new host records. However, only 4.3% of samples were positive for this species, and they were mostly in the east of the study area and had fewer larvae than the positive H. punctigera samples. H. punctigera larvae were found in each of six habitats, being, in order of mean numbers per sample: sandy deserts > floodplains > mulga, grasslands and saltbush > stony downs. Host status was determined for both species by plotting relative incidence against relative abundance, and the good hosts for H. punctigera differed between habitats. We discuss the value and limitations of this approach for identifying key hosts in broad scale population dynamics, and primary hosts which may have close co-evolutionary histories with the insects.
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understanding heliothine lepidoptera heliothinae pests what is a host plant
Journal of Economic Entomology, 2014Co-Authors: J P Cunningham, Myron P. ZaluckiAbstract:Heliothine moths (Lepidoptera: Heliothinae) include some of the world's most devastating pest species. Whereas the majority of nonpest heliothinae specialize on a single plant family, genus, or species, pest species are highly polyphagous, with populations often escalating in size as they move from one crop species to another. Here, we examine the current literature on heliothine host-selection behavior with the aim of providing a knowledge base for research scientists and pest managers. We review the host relations of pest heliothines, with a particular focus on Helicoverpa armigera (Hubner), the most economically damaging of all heliothine species. We then consider the important question of what constitutes a host plant in these moths, and some of the problems that arise when trying to determine host plant status from empirical studies on host use. The top six host plant families in the two main Australian pest species (H. armigera and Helicoverpa punctigera Wallengren) are the same and the top three (Asteraceae, Fabaceae, and Malvaceae) are ranked the same (in terms of the number of host species on which eggs or larvae have been identified), suggesting that these species may use similar cues to identify their hosts. In contrast, for the two key pest heliothines in the Americas, the Fabaceae contains ≈1/3 of hosts for both. For Helicoverpa zea (Boddie), the remaining hosts are more evenly distributed, with Solanaceae next, followed by Poaceae, Asteraceae, Malvaceae, and Rosaceae. For Heliothis virescens (F.), the next highest five families are Malvaceae, Asteraceae, Solanaceae, Convolvulaceae, and Scrophulariaceae. Again there is considerable overlap in host use at generic and even species level. H. armigera is the most widely distributed and recorded from 68 plant families worldwide, but only 14 families are recorded as a containing a host in all geographic areas. A few crop hosts are used throughout the range as expected, but in some cases there are anomalies, perhaps because host plant relation studies are not comparable. Studies on the attraction of heliothines to plant odors are examined in the context of our current understanding of insect olfaction, with the aim of better understanding the connection between odor perception and host choice. Finally, we discuss research into sustainable management of pest heliothines using knowledge of heliothine behavior and ecology. A coordinated international research effort is needed to advance our knowledge on host relations in widely distributed polyphagous species instead of the localized, piecemeal approaches to understanding these insects that has been the norm to date.
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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
Bulletin of Entomological Research, 2000Co-Authors: Derek Maelzer, Myron P. ZaluckiAbstract: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.
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size of the first spring generation of Helicoverpa punctigera wallengren lepidoptera noctuidae and winter rain in central australia
Australian Journal of Entomology, 1999Co-Authors: Anne Oertel, Gary P. Fitt, Myron P. Zalucki, Derek Maelzer, R W SutherstAbstract:Serious infestations of Helicoverpa punctigera are experienced yearly in the eastern cropping regions of Australia. Regression analysis was used to determine whether the size of the first generation in spring (G1), which is comprised mostly of immigrants from inland Australia, was related to monthly rainfall in inland winter breeding areas. Data from two long series of light-trap catches at Narrabri in New South Wales (NSW) and Turretfield in South Australia (SA) were used in the analyses. The size of G1 at Narrabri in each year was significantly regressed on the amount of rainfall in western Queensland and NSW in May and June. The size of G1 at Turretfield each year was significantly regressed on the amount of rain in May, June and July in western Queensland and NSW and also in the desert of central Western Australia. Low r2 values of the regressions suggest that rainfall data for more sites, as well as biological and other physical factors, such as temperature, evaporation, and prevailing wind systems, may need to be included to improve forecasts of the potential magnitude of the infestations in coastal cropping regions.
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analysis and interpretation of long term light trap data for Helicoverpa punctigera lepidoptera noctuidae in australia population changes and forecasting pest pressure
Bulletin of Entomological Research, 1996Co-Authors: D Maelzer, Myron P. Zalucki, R LaughlinAbstract:Using regression analysis the early season dynamics of Helicoverpa punctigera (Wallengren) were determined from long series of light trap catches (10-19 years) from three sites in Australia (Narrabri and Trangie in New South Wales, and Turretfield in South Australia). The size of the second spring generation (G, the one causing major pest problems in summer cropping regions) was strongly related to the size of the first spring generation (G). In most cases, rainfall in early winter had a positive influence on the size of G, whereas rainfall in spring had a negative effect. Regressions were found to account for 49 to 93% of the annual variation in G, depending on site. The use of light trap catches and weather data to forecast pest levels from a few months to a few weeks in advance is discussed, along with the improved understanding of early season H. pundigera dynamics.