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Baoqian Lu Sharon Downes Lewis Wilson Peter Gregg Kristen Knight Greg Kauter Bruce McCorkell 《Entomologia Experimentalis et Applicata》2012,145(1):72-81
To verify current thresholds for Bollgard II® cotton in Australia, the impact of Helicoverpa spp. (Lepidoptera: Noctuidae) larvae on yield, development, and quality under various infestation intensities and durations, and stages of growth, was tested using small plot field experiments over two seasons. Infestation with up to 80 eggs m?1 of Helicoverpa armigera (Hübner) and Helicoverpa punctigera Wallengren showed that species, infestation level, and stage of growth had no significant effect on yields of seed‐cotton or lint and on maturity and fibre quality. The duration of infestation of white flowers with H. punctigera neonates (maximum of every day for up to 4 weeks) had no impact on the yield of seed‐cotton or lint, maturity, and fibre quality, but when 100% of flowers were infested (compared with 0 or 50%), seed‐cotton and lint yields were significantly reduced and maturity was delayed. Infestation with up to 18 medium H. armigera larvae m?1 at several plant stages did not significantly affect yields of seed‐cotton and lint, maturity, and fibre quality. A heliocide spray applied on a commercial farm at the current threshold resulted in a significantly higher lint yield, compared with a farm where no spray was applied. In conclusion, Bollgard II® cotton is highly resistant to Helicoverpa spp. infestation. 相似文献
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Md Habibullah Bahar John Stanley Peter Gregg Alice Del Socorro 《Entomologia Experimentalis et Applicata》2013,146(2):224-231
Experiments were conducted in small arenas and on whole plants to explore the effect of cotton aphids, Aphis gossypii Glover (Hemiptera: Aphididae), as alternative prey on the predation of Helicoverpa armigera Hübner (Lepidoptera: Noctuidae) larvae by green lacewing larvae, Mallada signatus Schneider (Neuroptera: Chrysopidae). Transgenic Bt (Bollgard II®) and conventional cotton plants were included to explore potential differences in the predator's performance on these cotton types. In small arenas, the presence of 20 aphids reduced predation on H. armigera larvae by 22% (from 5.5 to 3.3 of 10) by a single lacewing larva over a 24‐h period. The presence of H. armigera reduced predation on aphids by ca. 29% (from 16.8 to 11.0 of 20) over 24 h. On whole plants, the presence of alternative prey had no effect on the number of H. armigera larvae or aphids remaining after 3 days. The presence of H. armigera larvae alone, without the predator, caused a 24% reduction in the numbers of aphids on conventional, but not on Bt cotton plants. The combination of Bt cotton and lacewing larvae caused a 96.6% removal of early‐stage H. armigera larvae, a statistically significant increase over the addition of the proportions (91.6%) removed by each factor measured separately, providing evidence of synergism. These studies suggest that the presence of aphids as alternative prey would not necessarily disrupt the predation by green lacewing on larvae of H. armigera, especially on Bt cotton. 相似文献
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This study was conducted to determine the effects of Bt cotton leaves (Bollgard II), non-Bt cotton leaves, and a mixture of
Bt+non-Bt cotton leaves on larval orientation behavior, survival and development of Trichoplusia ni in the laboratory. Results indicate that in a no-choice test, more first and fifth instars remained on Bt leaves than the
third instars. All larvae that remained on the leaves gradually moved to leaf edge. In the choice between a Bt and a non-Bt
leaf, more first instars moved to non-Bt leaves, whereas the third and fifth instars did not show significant difference in
the first 8 h, but eventually more moved to non-Bt leaves. More first instars fed non-Bt leaves than third instars and fifth
instars. When larvae fed Bt leaves, 100% of first instars, 92.7% of third instars and 51.1% of fifth instars died in 108 h.
Once larvae pupated, >90% developed to adults. First and third instars that fed Bt leaves developed slower but their pupae
developed faster than those on Bt+non-Bt leaves, whereas fifth instars developed similar on the three types of leaves. First
and third instars that fed Bt+non-Bt leaves resulted in less heavy pupae than those fed non-Bt leaves; whereas the fifth instars
that survived on Bt leaves produced lighter pupae. 相似文献
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Maria Esmeralda C. Sousa Valéria Wanderley-Teixeira Álvaro A.C. Teixeira Luiz C. Alves 《Journal of insect physiology》2010,56(12):1913-1919
The interaction of Cry toxins from Bacillus thuringiensis in the midgut of some insect larvae determines their efficacies as insecticides, due to the expression and availability of sites of action of the toxin in the midgut. Researches point out cases of resistance to Cry toxin due to alterations in the binding sites in columnar cell membrane. We analyzed the effects of Cry1Ac toxin expressed by Bt-cotton plants on Alabama argillacea midgut morphophysiology clarifying in levels of morphological and ultrastructural. Larvae in the 4th instar of A. argillacea after 20 min from ingesting Bt-cotton leaves expressing 0.183 ng of Cry1Ac exhibited ultrastructural and morphological modifications in the columnar cells with significant changes in the mitochondrial polymorphism, cytoplasmic vacuolization, microvillus and basal labyrinth. Expressive morphological alterations were also observed in the goblet cells indicating that the columnar cells are not the only target of the Cry1Ac toxin. The regenerative cells did not modify their structures and exhibited decrease in regeneration capacity. In conclusion, the ingestion of 0.183 ± 0.077 ng of Cry1Ac was enough to promote alterations in the columnar and goblet cells, besides reducing significantly the number of regenerative cells, which may have contributed to larval death. Nevertheless, further studies are necessary to determine the true cause of death. 相似文献
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