Developing guidelines for monitoring non-target effects of Bt crops

Possible consequences from the widespread planting of Bt crops have been reconsidered in light of laboratory studies showing that both non-target herbivores and beneficial insects may be adversely affected without feeding directly on Bt crops (Hilbeck et al. 1998, Losey et al. 1999, Jesse and Obrycki 2000, Dutton et al. 2002, Ponsard et al. 2002).Though not proving any harm to the environment, these laboratory studies suggest assessing the unintended effects of Bt crops is more complex than anticipated. However, because Bt crops are not grown in controlled environments, field trials will likely continue to be the final standard by which their benefits and risks are assessed

Influencing European Corn Borer (Lepidoptera: Crambidae) Aggregation Sites in Small Grain Crops

Reliable methods to attract European corn borer, Ostrinia nubilalis (Hübner), adults to small grain crops could be used to aggregate moths into small well-defined areas for control purposes or could be used in a resistance management program for delaying potential O. nubilalis resistance to transgenic corn. The objective of this research was to determine whether small-grain crops could be managed to influence O. nubilalis aggregation behavior. In farmer-managed oat, Atena sativa (L.), fields, more O. nubilalis adults were attracted to high-density patches of oat compared with standard patches of oat; no difference was found between patches of high-density oat and brome, Bromus spp. Numbers of O. nubilalis moths found in 6 barley, Hordeum vulgare (L.), and legume treatments (1995), and 4 oat/legume treatments (1996) were significantly different. The highest number of O. nubilalis adults were observed in barley planted with alfalfa, Medicago sativa (L.), followed by barley planted with crimson clover, Trifolium incarnatum(L.), barley planted with berseem, Trifolium alexandrinum (L.), barley planted with black medic, Medicago lupulina (L.), barley alone, and barley planted with lespedeza, Lespedeza stipulacea (Maximowicz). Double-planted oat attracted the highest number of O. nubilalis adults followed by oat planted with crimson clover, oat planted with alfalfa, and single-planted oat. Each study suggests that there is a positive correlation between moth aggregation and canopy area. Suggestions are made that timing canopy closure of a small-grain crop with peak O. nubilalis flight should maximize O. nubilalis aggregation and should thereby increase the efficacy of any control measures

Effects of Bt plants on non-target herbivores

INTRODUCTION Transgenic (genetically modified) crops producing insecticidal toxins derived from Bacillus thuringiensis (Bt) bacteria have been scrutinised by government agencies, scientists and the public for their potential to negatively impact non-target organisms in or surrounding agricultural habitats. While several crops have been engineered to express one or more Bt toxins, it is such com (= maize) varieties that have had commercial success. Many strains of Bt exist, each producing one or more toxic crystalline (Cry) proteins, but the deleterious effects of each toxin are usually confined to a few related species in a single order of insects. The species to which an ingested Bt toxin may be harmful is defined by the specific pH levels, enzymes, and gut receptors required to solubilise, activate and bind the toxin. The first commercial Bt-com varieties were produced to control the European com borer ( Ostrinia nubilalis) and other closely related pest moths, making any organism outside this group a non-target species. However, the specific requirements for a toxin to function have caused non-target research to be focused on herbivores, specifically non-pest moths and butterflies. The possibility that use of Bt crops negatively impacts predators and parasitoids that help regulate pest populations is considered elsewhere in this volume

Ecological Safety Assessment of Insecticidal Proteins Introduced into Biotech Crops

Crops genetically engineered to express insecticidal proteins have been used in U.S. agriculture since 1996 and are being increasingly adopted worldwide. The ecological safety of these crops has been extensively considered by regulatory agencies prior to their commercial release, and is confirmed by a growing body of published research and experience under a variety of environments and management regimes. Ecological risk assessment provides a framework to understand the safety of these crops by considering the hazard potential of the expressed proteins in conjunction with environmentally relevant exposure scenarios. The ecological risk assessment framework applied to plant-expressed insecticidal proteins also provides insights into data and assessment requirements for forthcoming transgenic crops

Development of a Model System Approach for Generating Fragments of the Cry1Ab Protein

The use of transgenic crops expressing one or more crystal (Cry) proteins for insect management has grown dramatically since their introduction nearly 2 decades ago. However, many questions surrounding the environmental fate of these proteins still persist. One area of particular interest is the possible detection of Cry protein fragments by the antibodies used in ELISA kits. A model system approach is used to generate environmentally relevant fragments by simulating conditions and digestive enzymes that are known to exist in environments in which Cry proteins may be present. Seven different types of model systems were screened for their ability to generate fragments of the Cry1Ab protein; five of these model systems reliably generated Cry1Ab fragments. These fragments were analyzed in a subsequent study to determine whether the fragments were still detectable by ELISA and whether they retained any bioactivity

Role of biotechnology in sustainable agriculture

A basic concept of sustainable agriculture includes using resources in a way that does not deplete or permanently damage systems used for plant and animal production. In early history, humans survived as hunter–gatherers and perhaps less than 1% of biomass could be used as food (Diamond, 1997). As a result, most resources in the environment were not likely to be used directly by humans. The limited availability of food also restricted population growth, helping to make the hunter–gatherer way of life sustainable. In contrast, domestication of crops and animals for food has greatly increased edible biomass, leading to dramatic population growth and the possibility that production of adequate food will lead to longterm damage to agricultural systems

A Review of Cry Protein Detection with Enzyme-Linked Immunosorbent Assays

The widespread use of Cry proteins in insecticide formulations and transgenic crops for insect control has led to an increased interest in the environmental fate of these proteins. Although several detection methods are available to monitor the fate of Cry proteins in the environment, enzyme-linked immunosorbent assays (ELISAs) have emerged as the preferred detection method, due to their cost-effectiveness, ease of use, and rapid results. Validation of ELISAs is necessary to ensure accurate measurements of Cry protein concentrations in the environment. Validation methodology has been extensively researched and published for the areas of sensitivity, specificity, accuracy, and precision; however, cross validation of ELISA results has been studied to a lesser extent. This review discusses the use of ELISAs for detection of Cry proteins in environmental samples and validation of ELISAs and introduces cross validation. The state of Cry protein environmental fate research is considered through a critical review of published literature to identify areas where the use of validation protocols can be improved

Susceptibility and Aversion of Spodoptera frugiperda (Lepidoptera: Noctuidae) to Cry1F Bt Maize and Considerations for Insect Resistance Management

Bacillus thuringiensis (Bt) maize was developed primarily for North American pests such as European corn borer (Ostrinia nubilalis (Hübner)). However, most Bt maize products are also cultivated outside of North America, where the primary pests may be different and may have lower susceptibility to Bt toxins. Fall armyworm (Spodoptera frugiperda JE Smith) is an important pest and primary target of Bt maize in Central and South America. S. frugiperda susceptibility to Cry1F (expressed in event TC1507) is an example of a pest-by-toxin interaction that does not meet the high-dose definition. In this study, the behavioral and toxic response of S. frugiperda to Cry1F maize was investigated by measuring the percentage of time naïve third instars spent feeding during a 3-min exposure. S. frugiperdaalso were exposed as third instars to Cry1F maize for 14 d to measure weight gain and survival. S. frugiperda demonstrated an initial, postingestive aversive response to Cry1F maize, and few larvae survived the 14 d exposure. The role of susceptibility and avoidance are discussed in the context of global IRM refuge strategy development for Bt products

Enzyme‐linked immunosorbent assay detection and bioactivity of Cry1Ab protein fragments

The continuing use of transgenic crops has led to an increased interest in the fate of insecticidal crystalline (Cry) proteins in the environment. Enzyme‐linked immunosorbent assays (ELISAs) have emerged as the preferred detection method for Cry proteins in environmental matrices. Concerns exist that ELISAs are capable of detecting fragments of Cry proteins, which may lead to an overestimation of the concentration of these proteins in the environment. Five model systems were used to generate fragments of the Cry1Ab protein, which were then analyzed by ELISAs and bioassays. Fragments from 4 of the model systems were not detectable by ELISA and did not retain bioactivity. Fragments from the proteinase K model system were detectable by ELISA and retained bioactivity. In most cases, ELISAs appear to provide an accurate estimation of the amount of Cry proteins in the environment, as detectable fragments retained bioactivity and nondetectable fragments did not retain bioactivity

Dissipation of double‐stranded RNA in aquatic microcosms

Silencing genes of a pest with double‐stranded RNA (dsRNA) is a promising new pest management technology. As part of the environmental risk assessment for dsRNA‐based products, the environmental fate and the potential for adverse effects to on‐target organisms should be characterized. In the present study, a nonbioactive dsRNA was spiked into the water column of a water and sediment microcosm to mimic drift from a spray application run off of unbound dsRNA or transport of plant tissues. Dissipation of dsRNA in the water column and partitioning into sediment was determined. The dsRNA rapidly dissipated in the water column and was below the limit of detection after 96 h. The levels detected in the sediment were not significant and may indicate rapid degradation in the water column prior to partitioning to sediment