Toxicity of Bacillus thuringiensis CrylAb Toxin to the Predator Chrysoperla carnea (Neuroptera: Chrysopidae)

Abstract

Laboratory feeding studies were carried out to determine the effects of the Bacillus thuringiensis (Berliner) CrylAb toxin on developmental time and mortality of Chrysoperla cameo (Stephens) larvae. A bioassay technique was developed that allowed for incorporation of the Cry lAb toxin into a liquid diet that was then encapsulated within small paraffin spheres. Because only 2nd and 3rd instars can penetrate the surface of the paraffin spheres, 2 different methods were used to rear chrysopid larvae through the 1st instar. The 1st method used small foam cubes soaked in non-encapsulated, liquid diet (with or without Cry lAb). The 2nd method used Ephestia kuehniella (Hiibner) eggs as prey during the first instar (no Cry lAb exposure). After reaching the 2nd ins tar, all larvae received encapsulated, artificial diet with or without Cry lAb, respectively. When reared only on artificial diet containing CrylAb toxin, total immature mortality was significantly higher (57%) than in the respective untreated control (30%). Also, significantly more chrysopid larvae died (29%) that received Cry lAb later during their larval development compared with the respective control (17%). Although mortality was consistently higher, no or only small differences in developmental times were observed between Cry lAb-treated and untreated C. cameo larvae. C. cornea larvae required significantly more time to complete larval development when reared on artificial diet only than when reared first on E. kuehniella eggs followed by encapsulated artifical diet or on only E. kuehniella eggs, regardless of exposure to Cry lAb. These results demonstrate that Cry lAb is toxic to C. cameo at 100 J.tmgl ml of diet by using encapsulated artificial diet.

Genetically engineered (modified) crops (Bacillus thuringiensis crops) and the world controversy on their safety

“…This study confirmed that Bt crops are not harmful to the two-spotted ladybird (Romeis et al 2012). Hilbeck et al (1998), in laboratory studies, fed 2nd and 3rd larval instars of the predator, Chrysoperla carnea on artificial diet mixed with Cry1Ab toxin. They found that the total mortality in larvae was significantly higher (57%) than in the untreated control (30%).…”

Setting the record straight: a rebuttal to an erroneous analysis on transgenic insecticidal crops and natural enemies

“…Hilbeck et al (1998a) observed reduced fitness of C. carnea larvae when fed on Bt maize-reared lepidopteran larvae and claimed it was associated with the CrylAb protein and that CrylAb is toxic to C. carnea (Hilbeck et al 1998b). However, subsequent studies clearly demonstrated that Cry1A proteins are not toxic to C. carnea larvae (Romeis et al 2004;Rodrigo-Simón et al 2006;Lawo and Romeis 2008) and that these proteins do not bind to the midgut of C. carnea, a prerequisite for toxicity (RodrigoSimón et al 2006).…”

Ecological Impacts of Genetically Modified Crops: Ten Years of Field Research and Commercial Cultivation

“…Adverse effects on mortality, longevity or development of predators were only reported in studies using Bt-susceptible lepidopteran larvae as prey that had ingested the Bt-toxin. In particular, the green lacewing (Chrysoperla carnea), an important predator in many maize growing areas, has thoroughly been studied since studies suggested that this predator was negatively affected by Cry1Ab [31][32][33]. Results of subsequent studies using several different prey species reared on Cry1Ab-maize, however, showed that the insecticidal protein itself does not directly affect this predator, but that the green lacewing may be affected when feeding on prey species that are susceptible to Bttoxin [34][35][36].…”