Assessing the risks of insect resistant transgenic plants on entomophagous arthropods: Bt-maize expressing Cry1Ab as a case study

One of the primary concerns related to the adoption of insect resistant transgenic plants in the environment is the detrimental effect that these may pose on non-target organisms, including entomophagous arthropods (parasitoids and predators) which have an important function in regulating pests. Despite the fact that regulatory bodies require information regarding the potential risk of releasing transgenic plants in the environment, to date, no specific protocols have been designed for assessing the risks of insect resistant transgenic crops on entomophagous arthropods. Here a framework for risk assessment is proposed to evaluate the effects of insect resistant plants on entomophagous arthropods. Using maize expressing the Bacillus thuringiensis gene which codes for the Cry1Ab toxin, we illustrate the procedure necessary for assessing the risks. As a first step, it is required to determine which entomophagous arthropods play a major role in regulating maize pests, and which may be at risk. Because the risk which transgenic plants pose to entomophagous arthropods depends on both, their exposure, and their sensitivity to the insecticidal protein, it is essential to determine, as a second step, if and at what level organisms are exposed to the transgene compound. Exposure will be associated with the feeding behaviour of phytophagous and entomophagous arthropods together with the tissue and cell specific temporal and spatial expression of the insecticidal protein. For those organisms which could potentially be exposed to the insecticidal protein, sensitivity tests, as a third step, should be performed to assess toxicity. The testing procedure and the type of tests which should be adopted to quantify the effects of insect resistant plants on natural enemies are subsequently illustrated. Taking the green lacewing Chrysoperla carnea as an example, we propose a procedure on how to perform tests and give evidence that Bt-maize poses no risk to this predator.