Indian Bt Cotton Varieties Do Not Affect the Performance of Cotton Aphids (original) (raw)
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Aphid honeydew quality as a food source for parasitoids is maintained in Bt cotton
PloS one, 2014
Bt-transgenic cotton has proven to be highly efficient in controlling key lepidopteran pests. One concern with the deployment of Bt cotton varieties is the potential proliferation of non-target pests. We previously showed that Bt cotton contained lower concentrations of insecticidal terpenoids as a result of reduced caterpillar damage, which benefited the aphid Aphis gossypii. It is thus important that non-target herbivores are under biological control in Bt cotton fields. The induction or lack of induction of terpenoids could also influence the quality of aphid honeydew, an important food source for beneficial insects. We therefore screened A. gossypii honeydew for cotton terpenoids, that are induced by caterpillars but not the aphids. We then tested the influence of induced insect-resistance of cotton on honeydew nutritional quality for the aphid parasitoid Lysiphlebus testaceipes and the whitefly parasitoid Eretmocerus eremicus. We detected the cotton terpenoids gossypol and hemi...
Field Evaluation of Bt Cotton Crop Impact on Nontarget Pests: Cotton Aphid and Boll Weevil
Neotropical Entomology, 2012
Bt cotton plants expressing Cry1Ac protein have high specificity for the control of lepidopteran larvae. However, studies conducted in several countries have shown these plants have a differential impact on nontarget herbivores. The aim of this study was to compare the colonization rates and population abundance of the cotton aphid, Aphis gossypii Glover (Hemiptera: Aphididae) and the boll weevil, Anthonomus grandis Boheman (Coleoptera: Curculionidae), in plots of Bt (Nuopal) and non-Bt cotton (Delta Opal) in an experimental field in Brasilia, DF, Brazil. No difference was observed in the preference and colonization by winged aphids to plants from the two treatments. There was no significant difference in abundance of wingless aphids or in the production of winged aphids between treatments. Apparently, the parameters that control factors such as fecundity, survival, and dispersal were similar on both Bt and non-Bt plants. Monitoring of plants for coccinellids, a specialist predator of aphids, and ants that act on the dispersal of aphids among plants showed no significant difference between Bt and non-Bt plants, supporting the inference above. Regarding the effect on boll weevil, there was also no significant difference between treatments in the total number of fruiting structures attacked in each plot, the percentage of fruiting structures attacked per plant or on the number of weevils emerging from fruits with boll weevil damage from egglaying, when damaged fruit samples were held in the laboratory. Based on these results, we conclude that there is no impact of Bt cotton crop expressing Cry1Ac on the nontarget herbivores tested under field conditions.
Pest trade-offs in technology: reduced damage by caterpillars in Bt cotton benefits aphids
Proceedings of the Royal Society B: Biological Sciences, 2013
The rapid adoption of genetically engineered (GE) plants that express insecticidal Cry proteins derived from Bacillus thuringiensis (Bt) has raised concerns about their potential impact on non-target organisms. This includes the possibility that non-target herbivores develop into pests. Although studies have now reported increased populations of non-target herbivores in Bt cotton, the underlying mechanisms are not fully understood. We propose that lack of herbivore-induced secondary metabolites in Bt cotton represents a mechanism that benefits non-target herbivores. We show that, because of effective suppression of Bt-sensitive lepidopteran herbivores, Bt cotton contains reduced levels of induced terpenoids. We also show that changes in the overall level of these defensive secondary metabolites are associated with improved performance of a Bt-insensitive herbivore, the cotton aphid, under glasshouse conditions. These effects, however, were not as clearly evident under field conditions as aphid populations were not correlated with the amount of terpenoids measured in the plants. Nevertheless, increased aphid numbers were visible in Bt cotton compared with non-Bt cotton on some sampling dates. Identification of this mechanism increases our understanding of how insect-resistant crops impact herbivore communities and helps underpin the sustainable use of GE varieties.
African Journal of Biotechnology, 2013
In the present work, we aimed to evaluate: 1) the influence of the Cry1Ac protein expressed by the genetically modified cotton variety ( Bt ) NuOpal, on the biological parameters of a non-target pest, Aphis gossypii , reared under laboratory conditions; 2) the influence of plant age on aphid development. Cotton cultivars were grown following technical advice. In the laboratory, the aphids were separated into plastic containers including a cotton sheet, which was changed daily with the help of a moist cotton cloth. Observations were carried out daily, and the duration of the immature and adult stages, and offspring number, were recorded. Our results show that regardless of the differences in the duration of each instar, cultivars Bt and non-Bt and the different ages of the plant to Bt, no differences were seen in the total duration of these phases. It was only during the reproductive period that differences were observed among genotypes for 120 days. Regarding the number of offspring...
Influence of cotton leaf sugars on cotton aphid, Aphis gossypii glover, populations
The study was conducted at the Texas Agricultural Experiment Station, Chillicothe, in the northern Texas Rolling Plains for four years from 1997 to 2000. The objective was to determine the relationship between nonstructural carbohydrates (glucose, fructose, sucrose) in cotton leaves and change in cotton aphid, Aphis gossypii Glover, numbers during late summer. The two whole plot treatments were cotton grown without irrigation (dryland) and irrigated cotton with last irrigation in late August. The two subplot treatments within each whole plot were an untreated check and a plot treated twice during the growing season with lambdacyhalothrin to stimulate aphid population increase. The sugar ratio (glucose + fructose/sucrose concentrations) was higher in irrigated plots compared with levels in dryland plots. Regression analysis indicated that change in aphid numbers was influenced by numbers of aphids per leaf, temperature, leaf moisture, and sugar ratio. A negative linear relationship was observed between change in aphid numbers and sugar ratio; population growth was limited by high levels of glucose and fructose in cotton leaves, especially when temperatures were high and leaf moisture low.
Environmental Entomology, 2008
Tri-trophic impacts of transgenic Bacillus thuringiensis (Bt) cotton GK12 and NuCOTN 99B were studied using a predator, the great lacewing Chrysopa pallens (Rambur), and its prey, the cotton aphid Aphis gossypii Glover, in laboratory feeding experiments. The parental nontransgenic cotton cultivar of GK12 was used as control. The predator was fed with uniform (aphids from a single cultivar) or mixed prey (aphids from the three cotton cultivars provided on alternate days). Mortality and development of the immature stages, pupal body mass, adult sex ratio, fecundity, and egg viability of C. pallens were measured. When fed GK12-originated aphid prey, pupal body mass of C. pallens was signiÞcantly higher than that of the control, more females emerged, and these females laid signiÞcantly more eggs. Other parameters were not impacted. Females emerging from larvae maintained on NuCOTN 99B-originated prey laid fewer eggs than those maintained on GK12. Other measurements did not differ signiÞcantly between the two Bt cotton cultivars. Compared with the control, mixed feeding signiÞcantly prolonged pupal development time and increased pupal body mass and percentage of females but did not affect other parameters. These results indicate that C. pallens is sensitive to aphid prey from different cotton cultivars. Transgenic Bt cotton GK12-originated aphid prey has no adverse impact on survival, development, and fecundity of C. pallens. Between the two Bt cotton cultivars, NuCOTN 99B-originated aphid prey provided to C. pallens in the larval stage may lower female fecundity. Mixed feeding of C. pallens with the two Bt cottonÐ originated prey and non-Bt prey may have some adverse impacts on pupal development.
Entomologia Experimentalis Et Applicata, 2012
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.
Advances in Life Sciences, 2016
Field trial was conducted to determine the effect of ecological factors on the incidence of insect pests on two hybrids of Bt and one non Bt cotton. Sucking insect pest viz. leafhopper, whitefly, thrips, aphid and mealybug remained active throughout the crop season with little differences among them and between Bt & non Bt version. Sucking pests was active from 31 st to 52 nd SMW (SMW i.e. July to December). The peak population of aphid was observed in 48 th SMW while leafhopper population reached to peak in 36 th SMW. The higher population of thrips was observed in 32 nd SMW while, whitefly incidence started from 33 rd SMW and remained below ETL during the season. Mealybug was found from 42 nd to 52 nd SMW. Predators of pests, lady bird beetle and Chrysoperla observed from 33 rd to 52 nd whereas spiders population started from the 31 st to 52 nd SMW. The correlation between predators (LBB and Chrysoperla) and aphid was found highly significant and positive. Aphid, whitefly and mealybug population were highly significant and negatively associated with minimum temperature and morning RH. Leafhopper showed significant positive correlation with minimum temperature and morning RH. Thrips population was highly significant and negatively correlated with maximum temperature and sunshine hours while it was positive correlated with minimum temperature, morning RH and evening RH. The bollworms were active 38 th to 48 th SMW but population of H. armigera; E. vittella and S. litura were peak in 43 th , 45th and 41 th SMW, respectively on non Bt version (DCH 32). The incidence of S. litura was almost nil throughout the season on RCH 2 BG I. Negligible population of H. armigera and E. vittella was observed on RCH 2 BG I but peak population was recorded in 43 rd and 46 th SMW, respectively. Incidence of Spodoptera was almost nil throughout the crop period in RCH 2 BG I. On RCH 2 BG II, the incidence of H. armigera; E. vittella and S. litura was almost nil throughout the season. Pink bollworm larvae and damage were observed early in 38 th SMW and continued till crop end on both Bt and non Bt version. E. vittella larval population showed negative and highly significant correlation with sunshine hours. The pink bollworm larval population showed positive correlation with maximum temperature. Moth catches of H. armigera and P. gossypiella showed highly significant and negative correlation with minimum temperature and morning relative humidity whereas; E. vittella showed significant negative correlation with maximum temperature. S. litura moth catches showed highly significant and positive association with maximum temperature
Tritrophic Association between Bt Cotton, Arthropod Pest and Natural Enemies
Cotton Research [Working Title], 2019
Benefits and harmful effects of Bt adoption technology are mainly related with cotton production where lot of insecticides are needed for management of arthropod herbivory and possible negative impact of crystalline Bt protein on parasitoids and predators is real. Therefore, current review information was focused that Bt should be selective for natural enemies and information was collected from different sources especially CAB abstracts as well as citations from many review articles and books. Usefulness of integrated pest management was highlighted with updated literature to cover the contents.
Journal of Economic Entomology, 2013
Cotton aphid, Aphis gossypii Glover, has a history of developing resistance to novel insecticides. A program is needed to monitor cotton aphid susceptibility to new insecticides. Concentration-mortality bioassays were conducted from 2008 to 2011 to monitor the susceptibility of cotton aphids from Þelds across the midsouthern United States to thiamethoxam and sulfoxaßor. Flonicamid was included in 2010 and 2011. Bioassays followed the procedures described by the Insecticide Resistance Action Committee for testing neonicotinoids against cotton aphid. Mortality was rated at 48 and 72 h. These bioassays suggest that high levels of resistance to thiamethoxam occur in cotton aphid throughout the midsouthern United States. Resistance ratios ranged from 0.9 to 562.6 at 48 h, and from 0.9 to 29.1 at 72 h. Aphid colonies tested were considered susceptible to ßonicamid and sulfoxaßor. The LC 50 values ranged from 1.43 to 6.60 ppm for ßonicamid. The LC 50 values for sulfoxaßor ranged from 1.01 to 5.85 ppm and 0.92Ð 4.13 ppm at 48 and 72 h, respectively. These values represent the baseline variability of the susceptibility of cotton aphid to ßonicamid and sulfoxaßor. The moderate level of variability observed combined with the high level of efÞcacy at low rates and the high reproductive rate of cotton aphid suggests that an effective resistance management plan needs to be devised for these insecticides. Flonicamid and sulfoxaßor should provide effective control of cotton aphid in areas where thiamethoxam resistance occurs. However, these insecticides need to be incorporated into a rotation strategy to preserve their efÞcacy against cotton aphid.