Risk assessment of Cry toxins of Bacillus thuringiensis on the predatory mites Euseius concordis and Neoseiulus californicus (Acari: Phytoseiidae)

Abstract

Genetically modified plants carrying Cry toxins of Bacillus thuringiensis (Bt) are widely used for pest control. Possible adverse effects as a result of the use of this control technique to non-target organisms is still a concern; however, few studies have addressed the effects of Bt crops on phytoseiid predatory mites. Phytoseiids are important for the natural control of phytophagous mites, but they can also feed on pollen, plant exudates, etc. Thus, phytoseiids may ingest Bt toxins through several pathways. In this paper, we evaluate the direct effect of Bt-toxins by feeding the predators on Bt cell suspensions, on solution of a Bt toxin and the tri-trophic effect by Bt expressed in transgenic plants. We present a method of conducting toxicological tests with Phytoseiidae which can be useful in studies of risk analysis of toxins to be expressed by genetically engineered plants. This method was used to evaluate the potential effect of ingestion of suspensions of Bt (1.25 × 10(8) spores/ml) and of purified protein Cry1Ia12 (0.006 mg/ml and 0.018 mg/ml) on Euseius concordis, a predatory mite that develops and reproduces best on pollen. The effects of genetically modified Bollgard(®) cotton, which carries the Cry1Ac protein, on Neoseiulus californicus, a selective predator that feeds more on spider mites than on pollen or insects, was determined by feeding them with Tetranychus urticae reared in Bollgard(®) cotton and on the non-transgenic isoline. When E. concordis was fed with suspension of Bt isolate derived from product Dipel(®) PM, no significant effects were detected. Similarly, Cry1Ia12 Bt toxin, at a concentration of 0.006 mg/ml, did not affect E. concordis. At a concentration of 0.018 mg/ml, however, the intake of this protein reduced the reproduction of E. concordis. There were no effects of Bollgard(®) cotton on the biological traits and on the predatory capacity of N. californicus. Results indicate that the Cry toxins of B. thuringiensis studied, at the concentrations used in the field or expressed in transgenic plants, should not affect the predatory mites E. concordis and N. californicus.

Purification of the insecticidal Cry2Ad protein from a Bt-isolated BRC-HZP10 strain and toxin assay to the diamondback moth, Plutella xylostella (L.)

“…The fecundity and egg hatchability of the population were affected, indicating that this protein can be used as a potential agent to control P. xylostella. de Castro et al (2013) found that the fecundity decreased slightly, while the duration of oviposition significantly shortened at a Cry1Ia12 concentration of 0.006 mg/mL in the study on effect of the Bt suspending agent and Cry1Ia12 on the non-target insects, Euseius concordis and Neoseiulus californicus, which was consistent with results in this study. Chen et al (2012) found that Cry1Ab transgenic rice KMD2 can extend the pupal duration of Nilaparvata lugens, decrease the number of eggs laid on each of rice tillerings, and significantly reduce fecundity.…”

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

“…Most studies indicated that transgenic crops had no adverse effects on either Aphis gossypii or Adelphocoris suturalis (Lawo et al 2009;. Beneficial insects such as predatory mites (Obrist et al 2006;de Castro et al 2012), green lacewings (Chrysoperla carnea) (Romeis et al 2004;Li et al 2008) and beetles (Ferry et al 2007) were also unaffected. In contrast, some researchers observed high mortality rates among the larvae of ladybird beetle (Adalia bipunctata) reared on diets with Bt toxic protein (Hilbeck et al 2012).…”