Long‐term impacts of elevated carbon dioxide and transgenic Bt cotton on performance and feeding of three generations of cotton bollworm

Abstract

The effects of elevated carbon dioxide (CO 2 ) on growth, metabolism, and performance of three generations of cotton bollworm, Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae), were studied. The insects were continuously fed transgenic Bacillus thuringiensis (Berliner) (Bt) cotton [ Cry1A (c) ] grown in open-top chambers. Two levels of CO 2 (ambient and 2 × ambient) and two cotton cultivars (non-transgenic Simian-3 and transgenic Bt GK-12) were used and bollworm larvae were reared on all four treatment combinations for three generations. CO 2 level and cotton variety significantly affected the growth and food digestibility parameters of H. armigera , with the exception of larval consumption rate for cotton variety. Overall, elevated CO 2 and transgenic Bt cotton both increased larval lifespan, food consumption rate, relative consumption rate, and approximate digestibility, while decreasing pupal weight, survival rate, fecundity, frass output, relative and mean relative growth rates (RGR/MRGR), and the efficiency of conversion of ingested and digested food (ECI/ECD). Moreover, there were significant CO 2 *variety interactions on pupal weight and ECD, and CO 2 *generation interactions on pupal weight, frass output, and MRGR. Furthermore, transgenic Bt cotton significantly decreased the population-trend index compared to non-transgenic cotton for the three successive bollworm generations, especially at elevated CO 2 . Damage inflicted by the cotton bollworm on cotton, irrespective of the presence of insecticidal genes, is predicted to be higher under elevated CO 2 conditions because of individual compensatory feeding on host plants. Conversely, population abundance is presumed to be lower under elevated CO 2 compared to that under ambient CO 2 , particularly in combination with transgenic technologies.

Temporal allocation of metabolic tolerance to transgenic Bt cotton in beet armyworm, Spodoptera exigua (Hübner)

“…Chen et al [37] reported that the population-trend index of cotton bollworm decreased significantly when fed on Bt cotton, compared with the non-Bt cotton fed control. Plutella xylostella fed on a diet containing Bt laid fewer eggs with lower viability, had reduced larval survival and adult eclosion rates, and ultimately reduced fecundity [38,39].…”

How does atmospheric elevated CO2 affect crop pests and their natural enemies? Case histories from China

“…Chen et al (2007) reported that consumption by cotton bollworm under elevated CO 2 is higher than that under an ambient CO 2 condition. Thus, it is necessary to assess consumption and density of cotton bollworm to differentiate between these effects.…”

“…Meanwhile, the decreased foliar nitrogen level reduces leaf nutritional quality, diminishing the value of foliage as a resource for insect herbivores (Johns & Hugher, 2002). This indicates that the nitrogen dilution effect of elevated CO 2 increased mortality, reduced fecundity and reduced the density of cotton bollworm larvae through three successive generations when fed on wheat, cotton and maize, respectively (Wu et al, 2006;Chen et al, 2007;Yin et al, 2010). Thus, elevated CO 2 negatively affects cotton bollworm via the host plant.…”

Feeding Preference and Movement of <I>Nezara viridula</I> and <I>Euschistus servus</I> (Hemiptera: Pentatomidae) on Individual Cotton Plants

“…Because boll size and location could not be randomized, they are confounded in these data. Although not examined as part of this experiment or any other experiments with stink bugs feeding on cotton, it is possible that preferential feeding on a speciÞc boll size could be inßuenced by agronomic or environmental factors that affect boll growth characteristics (Chen et al 2005(Chen et al , 2007Adhikari and Parajulee 2008). However, that hypothesis is tempered by the fact that Ͼ50% of all bolls in this experiment exhibited feeding damage, thereby suggesting that the bugs were actively among all bolls on the plant.…”