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Cotton Aphid (cotton + aphid)
Selected AbstractsEffect of temperature and host stage on performance of Aphelinus varipes Förster (Hym., Aphelinidae) parasitizing the cotton aphid, Aphis gossypii Glover (Hom., Aphididae)JOURNAL OF APPLIED ENTOMOLOGY, Issue 10 2002O. Röhne Development time, mummification, pupal mortality, host feeding and sex ratio of a Norwegian strain of Aphelinus varipes Förster parasitizing the cotton aphid, Aphis gossypii Glover were studied at 20, 25 and 30°C in controlled climate cabinets. Petri dishes with cucumber (Cucumis sativus L) leaves on agar were used as experimental units. Cotton aphids in different larval instars and as adults, reared at the three different temperatures, were presented to A. varipes in a `no-choice' situation for 6 h. These presentations were done at 25°C in each experiment to avoid an influence of temperature on parasitization rate. More first instar aphids were parasitized than third and fourth instars among the aphids reared at 20°C. Pupal mortality of the parasitoid was not influenced by temperature. It was lower in aphids parasitized as adults than in aphids parasitized in second instar. The sex ratio of A. varipes was female-biased, and varied between 92% females developed from aphids reared at 25°C and 70% from aphids reared at 20°C. The sex ratio was not significantly influenced by host stage. The development time of A. varipes ranged from 17.5 days at 20°C to 9.8 days at 30°C. [source] Differential mRNA expression levels and gene sequences of carboxylesterase in both deltamethrin resistant and susceptible strains of the cotton aphid, Aphis gossypiiINSECT SCIENCE, Issue 3 2008Chuan-Wang Cao Abstract Extensive use of insecticides on cotton has prompted resistance development in the cotton aphid, Aphis gossypii (Glover) in China. A deltamethrin-selected population of cotton aphids from Xinjiang Uygur Autonomous Region, China with 228.59-fold higher resistance to deltamethrin was used to examine how carboxylesterase conferred resistance to this pyrethroid insecticide. The carboxylesterase activity in the deltamethrin-resistant strain was 3.67-, 2.02- and 1.16-fold of the susceptible strain when using ,-naphthyl acetate (,-NA), ,-naphthyl acetate (,-NA) and ,-naphthyl butyrate (,-NB) as substrates, respectively. Carboxylesterase cDNA was cloned and sequenced from both deltamethrin-resistant and susceptible strains. The cDNA contained 1581 bp open reading frames (ORFs) coding a 526 amino acid protein. Only one amino acid substitution (Val87 -Ala) was observed between deltamethrin-resistant and susceptible strains but it is not genetically linked to resistance by the catalytic triad and signature motif analysis. The real-time polymerase chain reaction analysis indicated that the resistant strain had a 6.61-fold higher level of carboxylesterase mRNA than the susceptible strain. The results revealed that up-regulation of the carboxylesterase gene, not modified gene structure, may be responsible for the development of resistance in cotton aphids to deltamethrin. [source] Effect of temperature and host stage on performance of Aphelinus varipes Förster (Hym., Aphelinidae) parasitizing the cotton aphid, Aphis gossypii Glover (Hom., Aphididae)JOURNAL OF APPLIED ENTOMOLOGY, Issue 10 2002O. Röhne Development time, mummification, pupal mortality, host feeding and sex ratio of a Norwegian strain of Aphelinus varipes Förster parasitizing the cotton aphid, Aphis gossypii Glover were studied at 20, 25 and 30°C in controlled climate cabinets. Petri dishes with cucumber (Cucumis sativus L) leaves on agar were used as experimental units. Cotton aphids in different larval instars and as adults, reared at the three different temperatures, were presented to A. varipes in a `no-choice' situation for 6 h. These presentations were done at 25°C in each experiment to avoid an influence of temperature on parasitization rate. More first instar aphids were parasitized than third and fourth instars among the aphids reared at 20°C. Pupal mortality of the parasitoid was not influenced by temperature. It was lower in aphids parasitized as adults than in aphids parasitized in second instar. The sex ratio of A. varipes was female-biased, and varied between 92% females developed from aphids reared at 25°C and 70% from aphids reared at 20°C. The sex ratio was not significantly influenced by host stage. The development time of A. varipes ranged from 17.5 days at 20°C to 9.8 days at 30°C. [source] PCR detection of pirimicarb resistance in Australian field isolates of Aphis gossypii Glover (Aphididae: Hemiptera)AUSTRALIAN JOURNAL OF ENTOMOLOGY, Issue 1 2009Martin O McLoon Abstract Aphis gossypii Glover (cotton aphid) is a major secondary pest of Australian cotton that readily develops resistance to the carbamate insecticide pirimicarb (Pirimor®) and to organophosphates generally. To test the pirimicarb resistance status of Australian strains of A. gossypii, a polymerase chain reaction (PCR) assay followed by restriction enzyme assay (REA) was designed to identify the AceI polymorphism S431F known to be responsible for resistance. The method was tested against reference and 33 field strains collected over two consecutive seasons. Both methods confirmed pirimicarb resistance in two field strains, one from each cotton season, giving credence to the molecular technique described. The PCR assay proved specific for the AceI gene. This PCR REA assay has the potential to replace bioassay for the routine pirimicarb resistance monitoring in A. gossypii. With the molecular assay providing results in 48 h, compared with 4,8 weeks for bioassay, such an assay could be used before insecticide control. [source] Differential mRNA expression levels and gene sequences of carboxylesterase in both deltamethrin resistant and susceptible strains of the cotton aphid, Aphis gossypiiINSECT SCIENCE, Issue 3 2008Chuan-Wang Cao Abstract Extensive use of insecticides on cotton has prompted resistance development in the cotton aphid, Aphis gossypii (Glover) in China. A deltamethrin-selected population of cotton aphids from Xinjiang Uygur Autonomous Region, China with 228.59-fold higher resistance to deltamethrin was used to examine how carboxylesterase conferred resistance to this pyrethroid insecticide. The carboxylesterase activity in the deltamethrin-resistant strain was 3.67-, 2.02- and 1.16-fold of the susceptible strain when using ,-naphthyl acetate (,-NA), ,-naphthyl acetate (,-NA) and ,-naphthyl butyrate (,-NB) as substrates, respectively. Carboxylesterase cDNA was cloned and sequenced from both deltamethrin-resistant and susceptible strains. The cDNA contained 1581 bp open reading frames (ORFs) coding a 526 amino acid protein. Only one amino acid substitution (Val87 -Ala) was observed between deltamethrin-resistant and susceptible strains but it is not genetically linked to resistance by the catalytic triad and signature motif analysis. The real-time polymerase chain reaction analysis indicated that the resistant strain had a 6.61-fold higher level of carboxylesterase mRNA than the susceptible strain. The results revealed that up-regulation of the carboxylesterase gene, not modified gene structure, may be responsible for the development of resistance in cotton aphids to deltamethrin. [source] BIOLOGY OF CHRYSOPA PHYLLOCHROMA WESMAEL (NEUROPTERA: CHRYSOPIDAE).INSECT SCIENCE, Issue 3 2004II: INTRASPECIFIC INTERFERENCE AND SEARCHING CAPACITY Abstract, The present study examined intraspecific interference and searching behavior of Chrysopa phyllochroma Wesmael (Neuroptera: Chrysopidae) for Aphis gossypii Glover (Homoptera: Aphididae) nymphs under laboratory and greenhouse conditions. The results were shown as follow: 1) In four different arenas (i.e. Petri dish, glass vessel, glass vessel with barriers in it, and cage with potted cotton plant), the predaceous efficiency of C. phyllochroma larvae varied with the predator density, the hunt constant (Q) and the intraspecific interference (m) increased with the prey density but decreased with the space heterogeneity; 2) In cage with potted cotton plant, the first- and second-instar green lacewing larvae consumed 13.6 and 29.4 cotton aphiddday respectively. The number of cotton aphids consumed by C. phyllochroma on lower leaves was significantly less than that on upper leaves; and 3) In cage with potted cotton plant, the percentage of the first- and second-instar green lacewing larvae located on upper leaves was significant less than that on lower leaves. [source] The ecological differentiation of asexual lineages of cotton aphids: alate behaviour, sensory physiology, and differential host associationsBIOLOGICAL JOURNAL OF THE LINNEAN SOCIETY, Issue 3 2009ADRIANA J. NAJAR-RODRÍGUEZ The cotton aphid (Aphis gossypii Glover) is a cosmopolitan pest species consisting of various host plant-associated lineages that appear to have different patterns of insecticide resistance, electrophoretic banding, and reproductive output across alternative host species. Debate continues as to whether these differences represent intraspecific variation or indicate a complex of cryptic or sibling species. We studied the host plant-related ecology of two asexual lineages of A. gossypii associated with the families Malvaceae and Cucurbitaceae, respectively, in particular the host plant finding and acceptance processes of the alate forms. The two lineages proved to be differentiated across host plants in terms of: (1) their landing and settling behaviour, nymphal production rate, and subsequent colony establishment (i.e. nymphal survival and development) and (2) their sensory abilities in relation to host plant-derived odours. Furthermore, genetic structuring according to host plant type was detected using the gene for elongation factor 1-,. The magnitude of the genetic differentiation across lineages was low, perhaps indicating a relatively recent divergence. The results demonstrate: (1) the presence of (at least) two cryptic species within the current definition of A. gossypii, as anticipated in previous studies, and (2) the practicalities of using a multidisciplinary approach to understanding the ,limits' of asexual species. If sexuals can be generated from each of these lineages, this conclusion will be open to further testing. © 2009 The Linnean Society of London, Biological Journal of the Linnean Society, 2009, 97, 503,519. [source] | ||||||||||