A Comprehensive Assessment of the Effects of Bt Cotton on Coleomegilla maculata Demonstrates No Detrimental Effects by Cry1Ac and Cry2Ab

Abstract

The ladybird beetle, Coleomegilla maculata (DeGeer), is a common and abundant predator in many cropping systems. Its larvae and adults are predaceous, feeding on aphids, thrips, lepidopteran larvae and plant tissues, such as pollen. Therefore, this species is exposed to insecticidal proteins expressed in insect-resistant, genetically engineered cotton expressing Cry proteins derived from Bacillus thuringiensis (Bt). A tritrophic bioassay was conduced to evaluate the potential impact of Cry2Ab- and Cry1Ac-expressing cotton on fitness parameters of C. maculata using Bt-susceptible and -resistant larvae of Trichoplusia ni as prey. Coleomegilla maculata survival, development time, adult weight and fecundity were not different when they were fed with resistant T. ni larvae reared on either Bt or control cotton. To ensure that C. maculata were not sensitive to the tested Cry toxins independent from the plant background and to add certainty to the hazard assessment, C. maculata larvae were fed artificial diet incorporated with Cry2Ab, Cry1Ac or both at >10 times higher concentrations than in cotton tissue. Artificial diet containing E-64 was included as a positive control. No differences were detected in any life-table parameters between Cry protein-containing diet treatments and the control diet. In contrast, larvae of C. maculata fed the E-64 could not develop to the pupal stage and the 7-d larval weight was significantly negatively affected. In both feeding assays, the stability and bioactivity of Cry proteins in the food sources were confirmed by ELISA and sensitive-insect bioassays. Our results show that C. maculata is not affected by Bt cotton and is not sensitive to Cry2Ab and Cry1Ac at concentrations exceeding the levels in Bt cotton, thus demonstrating that Bt cotton will pose a negligible risk to C. maculata. More importantly, this study demonstrates a comprehensive system for assessing the risk of genetically modified plants on non-target organisms.

The end of a myth—Bt (Cry1Ab) maize does not harm green lacewings

“…Similarly, bioactivity of Cry proteins has been confirmed in sensitive insect bioassays for various other combinations of Bt plants, Cry proteins, and herbivores (Chen et al, 2008; Meissle and Romeis, 2009b; Li et al, 2011; Liu et al, 2011; Tian et al, 2012, 2013). …”

An Alcaligenes strain emulates Bacillus thuringiensis producing a binary protein that kills corn rootworm through a mechanism similar to Cry34Ab1/Cry35Ab1

“…Assays with C. maculata followed previously described protocols 35 except that test proteins were not replaced during the duration of the 7 day assay. For assays against Lepidoptera 25 µl of test proteins were topically applied to 100 µl of a Lepidoptera-specific artificial diet (Southland Products Inc., Lake Village, Arkansas) and allowed to dry before 2 to 3 neonate larvae were placed in each well.…”

Effects of Transgenic Bt Cotton on the Population Density, Oviposition Behavior, Development, and Reproduction of a Nontarget Pest, <I>Adelphocoris suturalis</I> (Hemiptera: Miridae)

“…Enzyme-linked immunosorbent assay (ELISA) has detected Bt toxic protein in both herbivorous pests and their natural enemies (Alvarez-Alfageme et al 2008;Torris and Ruberson. 2008;Li et al 2011;García et al 2012;Tian et al 2013). A resurgence of secondary pests such as aphids, spider mites, and mirid bugs has also been reported in transgenic crops (Wu et al 2002;Lu et al 2010;Zhao et al 2011).…”