Nontarget risk characterization relevance to ecological safety

As shown for these cases of current commercial plant insecticidal proteins, the ecological risk assessment for protein effects on nontarget organisms seeks first to establish the logic for potential exposure to entities of concern. A tiered process of testing and assessment is then used to validate the anticipated environmental effects through testing of both potentially susceptible nontargets and a suite of organisms thought to be nonsusceptible. The results of effects testing are interpreted in light of their relevance to reasonably anticipated route, source, frequency, intensity, and duration of exposure. Residual uncertainties are addressed with higher-tier testing and/or targeted monitoring. This process is recursive, in that the risk problem is reformulated and the risk assessment is revised as new knowledge concerning the protein and its ecological effects is established. This process has allowed for relevant ecological safety determinations for plant-expressed insecticidal proteins and can be adapted to new product innovations as they arise.

In some cases, broad questions of relevance to agro-ecosystem managements have been addressed using Bt crops as models. For instance, Wold et al.99 have observed that, given the effective elimination of pests targeted by incorporated Cry proteins, beneficial species using target species as prey or hosts could be reduced; thus, subtle changes to the structure of the arthropod community may be possible. However, some field studies suggest that Bt corn promotes greater populations of nontarget organisms relative to other pest management approaches,l00 whereas most detect no differences in levels of nontarget groups.l0l,l02

Summary of Nontarget Invertebrate Testing for WideStrike™ Cotton Expressing the CrylAc and Cry1 F Proteins96-98


Apis mellifera

Folsomia candida Chrisoperla carnea Nasonia vitripennis Hippodamia convergens

Common Name

Honeybee (larvae)


Green lacewing

(larvae) Parasitic wasp

Protein Source bacterial derived

Cry1Ac + Cry1F

cotton pollen bacterial derived bacterial derived bacterial derived

Ladybird beetle bacterial derived


1.98 |g Cry1F + 11.94 |g Cry1Ac per mL sugar water

200 mg pollen per mL sugar water

300 |g Cry1F + 22.5 |g Cry1Ac per mL sugar water

Effect Endpoint mean survival to emergence adult survival and reproduction mean survival to pupation mortality at 10 d mortality at 15 d

Resultb no effect LC50 > 4 x pollen expression no effect no effect at 10 x field level effect of dose in 1 of 2 studies LC50 >

14 x pollen expression no effect LC50 > 13 x pollen expression

Monarch (larvae) bacterial derived no effect LC50 > 780 x CrylF pollen expression and > 8 x CrylAc pollen expression EC50 > 105 x the dietary pollen exposure for CrylF and > 10 x the dietary pollen exposure for CrylAc no effect at 762 x and 3066 x field levels of CrylF and CrylAc, respectively no effect EC50 >l3,000 x and 395 x estimated aquatic exposure for CrylF and CrylAc, respectively a Unless otherwise noted, results are for proteins administered in combination. Comparable results for individual proteins are reported elsewhere (USDA, 2004b). b The toxicological finding is summarized relative to the high end exposure estimate for estimated environmental concentration of the protein(s).

Danaus plexippus

Eisenia fetida

Daphnia magna


Daphnid bacterial derived bacterial derived dose-response for indivdual proteins in artifical diet

107 mg Cry1Ac + 247 mg Cry1F per g diet

growth reduction after 7 d mortality at 14 d immobilization after 2 d o era c/> »

Pr ot ei n

4.8 Insect Resistance MANAGEMENT IN RELATIoN

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