Control Of European Corn Borer Research Articles

Evaluation of At-Plant Banded Applications of Verimark Versus Foliar Applications of Exirel for European Corn Borer Control on Green Bean in Wisconsin, 2021

Evaluation of At-Plant Banded Applications of Verimark Versus Foliar Applications of Exirel for European Corn Borer Control on Green Bean in Wisconsin, 2021

Parazitoidi roda Trichogramma (Hymenoptera: Trichogrammatidae), prirodni neprijatelji kukuruznog plamenca Ostrinia nubilalis Hübner, 1796 (Lepidoptera: Crambidae)

Maize (Zea mays Linnaeus, 1753) is economically the most important crop in Serbia, while the European corn borer Ostrinia nubilalis (Hübner, 1796) (Lepidoptera: Crambidae) is the its most significant pest of this crop. One of the potentially successful and environmentally friendly method for biological control of this pest is based on the usage of wasps from the genus Trichogramma Westwood, 1833 (Hymenoptera: Trichogrammatidae), which parasitize the egg clusters of European corn borer. From the aspect of biological control of agricultural pests, species of the genus Trichogramma represent the most important parasitoids of harmful Lepidoptera insects. The use of parasitoids of the genus Trichogramma in the biological control of agricultural pests is widely used in many developed countries. However, in certain geographical regions, including the Balkan countries, the potential of these insects in biological control has not yet been fully exploited. Native populations of this genus show a high practical potential in biological control that the agricultural sector of the Republic of Serbia does not use at all. The results of research conducted in Serbia, which show a high capacity for parasitism of indigenous species from local Trichogramma populations, especially when it comes to T. brassicae species, indicate the potential for commercial production of these beneficial insects and their targeted use in biological control of European corn borer. The aim of this review is to indicate the potential of parasitoids of the genus Trichogramma present on the territory of Serbia in programs of biological control of agricultural pests, primarily harmful Lepidoptera such as O. nubilalis.

European Corn Borer Control in Snap Bean, 2015: Table 1

European corn borer control (ECB) using foliar-applied insecticides was evaluated in a research snap bean field near Geneva, New York (GPS coordinates: 42.865500, -77.029667). On 25 June 2015, processing snap bean seeds were planted at a density of 23 seeds per m using a precision vacuum planter (Monosem Inc.). All seeds (including the non-insecticide control) were treated with thiamethoxam (Cruiser 5FS) and mefenoxam and fludioxonil (ApronMaxx) to protect seedlings against seed corn maggot, early infestations of potato leafhoppers and diseases. Natural ECB pressure in the research field is rarely high enough to sufficiently evaluate insecticide treatments on snap bean. To increase ECB pressure at the …

Relevance of Traditional Integrated Pest Management (IPM) Strategies for Commercial Corn Producers in a Transgenic Agroecosystem: A Bygone Era?

The use of transgenic Bt maize hybrids continues to increase significantly across the Corn Belt of the United States. In 2009, 59% of all maize planted in Illinois was characterized as a "stacked" gene variety. This is a 40% increase since 2006. Stacked hybrids typically express one Cry protein for corn rootworm control and one Cry protein for control of several lepidopteran pests; they also feature herbicide tolerance (to either glyphosate or glufosinate). Slightly more than 50 years has passed since Vernon Stern and his University of California entomology colleagues published (1959) their seminal paper on the integrated control concept, laying the foundation for modern pest management (IPM) programs. To assess the relevance of traditional IPM concepts within a transgenic agroecosystem, commercial maize producers were surveyed at a series of meetings in 2009 and 2010 regarding their perceptions on their use of Bt hybrids and resistance management. Special attention was devoted to two insect pests of corn, the European corn borer and the western corn rootworm. A high percentage of producers who participated in these meetings planted Bt hybrids in 2008 and 2009, 97 and 96.7%, respectively. Refuge compliance in 2008 and 2009, as mandated by the U.S. Environmental Protection Agency (EPA), was 82 and 75.7%, respectively, for those producers surveyed. A large majority of producers (79 and 73.3% in 2009 and 2010, respectively) revealed that they would, or had, used a Bt hybrid for corn rootworm (Diabrotica virgifera virgifera LeConte) or European corn borer (Ostrinia nubilalis Hübner) control even when anticipated densities were low. Currently, the EPA is evaluating the long-term use of seed blends (Bt and non-Bt) as a resistance management strategy. In 2010, a large percentage of producers, 80.4%, indicated they would be willing to use this approach. The current lack of integration of management tactics for insect pests of maize in the U.S. Corn Belt, due primarily to the escalating use of transgenic Bt hybrids, may eventually result in resistance evolution and/or other unforeseen consequences.

Crop residue chemistry, decomposition rates, and CO2 evolution in Bt and non-Bt corn agroecosystems in North America: a review

Corn (Zea mays L.) is a major cereal crop, with production on more than one-fifth of the agricultural land worldwide. In North America, about 50% of corn acreage is planted with transgenic corn hybrids such as those with the gene from Bacillus thuringiensis (Bt) that express the insecticidal crystalline protein (Cry1Ab) for the control of European corn borer (ECB, Ostrinia nubilalis Hubner). Widespread production of Bt corn could affect soil organic carbon (SOC) storage in agroecosystems if transgenic corn differs from conventional corn in yield and chemical composition. Generally, the yield of Bt corn is greater than non-Bt corn in years when there is severe infestation of corn insect pests. Some authors report that Bt corn has higher lignin content than non-Bt corn, whereas others found no difference in the chemical composition of near isolines. Residues with higher lignin content are expected to have a slower decomposition rate and release less CO2 to the atmosphere; however, this is not supported by the literature. A few studies have examined decomposition of Bt corn residues in this context, and the findings to date have been inconclusive, perhaps due to the variety of experimental approaches used to study this question. Generally, the literature supports the view that decomposition rates in Bt corn- and non-Bt corn-amended soils are similar. Whether Bt corn has greater lignin content or slower decomposition rates, the relevant question is whether this will affect the amount of C storage in the soil. A significant gain in SOC requires crop residue inputs with higher lignin content than what is realistically expected from Bt corn residue.

Timing clorpirifos + cypermethrin and indoxacarb applications to control European corn borer damage and fumonisin contamination in maize kernels

European corn borer (ECB) is the main maize pest in central and southern Europe and it promotes the infection of maize with Fusarium verticillioides, which is able to produce fumonisins. Field experiments were performed from 2006 to 2007 in northwestern Italy to determine the effects of the timing of insecticide applications on maize fungal ear rot and fumonisin contamination in natural infection conditions. Four application timings and two insecticides (clorpirifos + cypermethrin and indoxacarb) were compared each year. In both years, the treatments applied at the beginning of a consistent ECB flight activity and at the flight peak showed the best efficacy to control the insect damage on ears. Fungal ear rot and fumonisin contamination were clearly affected by ECB control. The efficacy of the best application timing to control fumonisin occurrence was 73% in 2006 and 84% in 2007. Earlier insecticide applications showed lower fumonisin contamination than treatments applied after the adult flight peak. The production of maize and maize-based foods with a low fumonisin content may be enhanced through correct insecticide application against the second ECB generation. The optimum timing of insecticides is between the beginning of a consistent adult flight activity and the flight peak.

Management of fumonisin contamination in maize kernels through the timing of insecticide application against the European corn borer Ostrinia nubilalis Hübner

The European corn borer (ECB), Ostrinia nubilalis, is the principal pest of maize in Central and South Europe. It is known to promote Fusarium verticillioides infection in maize grain, a recognized producer of fumonisins. Field experiments were performed in 2006 and 2007 in two sites in NW Italy to determine the effects of the timing of insecticide application on ECB damage, fungal ear rot and fumonisin contamination under natural conditions. Different insecticide application timings were compared, from maize flowering to approximately 15 days after the flight peak of adult ECB. At harvest, the ears were rated for incidence and severity of ECB damage, fungal ear rot symptoms and fumonisin (FB1 + FB2) contamination. In all years/sites, treatments applied at the beginning of consistent ECB flight activity were most effective in controlling insect damage on ears. Fungal ear rot and fumonisin contamination were significantly affected by ECB control. The efficacy of the best timing of insecticide application in controlling fumonisin contamination was, on average, 93% compared to the untreated control. Contamination levels of these mycotoxins increased with either an earlier or later treatment. Furthermore, an earlier insecticide application showed lower fumonisin contamination than a treatment applied after the adult flight peak. Production of maize kernels and maize-based foods that do not exceed the maximum international and EU permitted levels for fumonisins could be enhanced by appropriate insecticide treatment against second generation ECB. The optimum time for insecticide application is between the beginning of consistent adult flight activity and the flight peak.

Control of European Corn Borer in Bell Peppers with Chlorantraniliprole Applied Through a Drip Irrigation System

The European corn borer (ECB), Ostrinia nubilalis Hübner (Lepidoptera: Pyralidae), is the most important pest of bell peppers in New Jersey and weekly applications of insecticide sprays are needed to control this pest. Most pepper production (up to 80%) utilizes black plastic mulch with drip irrigation and high wooden stakes, limiting pesticide application equipment. A new chemistry insecticide, chlorantraniliprole, is highly soil systemic, very soluble, and effective against ECB at very low rates. Because of these properties, a 3-year study was undertaken beginning in 2004 and continuing in 2005 and 2007 applying chlorantraniliprole through a drip irrigation system in bell peppers for control of the ECB. Each year, on every harvest date examined, chlorantraniliprole injected through a drip irrigation system at either 0.05 or 0.07 kg·ha−1 was as effective, or more effective, in reducing percentage of ECB-infested peppers than a standard grower pesticide program of two applications of acephate followed by several applications of indoxycarb. All treatments resulted in significantly fewer ECB-infested peppers at harvest compared with untreated on all dates recorded each year.

Integration of Trichogramma ostriniae releases and habitat modification for suppression of European corn borer (Ostrinia nubilalis Hübner) in bell peppers

AbstractA two-year field study was conducted to evaluate the effectiveness of Trichogramma ostriniae Pang et Chen (T.o.) releases in combination with habitat modification, to enhance biological control of European corn borer (ECB), Ostrinia nubilalis Hübner, the key pest of bell peppers in Kentucky. A randomized block design with a split-plot treatment arrangement was used in both years. Buckwheat, Fagopyrum esculetum Moench, was inter-planted as a nectar source for the wasps and as an attractant for ECB natural enemies. Sentinel ECB egg masses were placed in each subplot to monitor establishment and dispersal of T. ostriniae within and between plots. Fruit were harvested at maturity, graded according to USDA standards, inspected for insect damage, and dissected to confirm ECB presence when evidence of entry was suspected, to determine percentage of infested fruits. Percent ECB infested fruit was reduced in plots with wasp releases and in plots with buckwheat inter-planted. The interaction of habitat modification and wasp releases significantly reduced pepper damage as a result of the synergy between tactics. Percentage of T. ostriniae parasitized sentinel eggs was significantly higher in wasp release plots compared to non-release plots. T. ostriniae releases used in conjunction with habitat modification for ECB control in bell peppers appears to be a promising alternative to traditional insecticide-based strategies for small-acreage and organic farms. This study displays an example system utilizing conservation biological control at a landscape level for pest suppression.

Field trials to evaluate effects of Bt-transgenic silage corn expressing the Cry1Ab insecticidal toxin on non-target soil arthropods in northern New England, USA

Traditionally, control of European corn borer (Ostrinia nubilalis) Hübner has been achieved through the use of chemical insecticides. With increasing emphasis on reducing pesticide inputs in agricultural production, alternative management technologies are now being used including transgenic silage corn modified to express Cry1Ab protein toxins derived from Bacillus thuringiensis (Bt) Berliner. The Cry1Ab toxin is expressed by all plant cells and throughout the growing season. Furthermore, the toxins are exuded from corn plant roots into the rhizosphere, raising concerns over possible side-effects on non-target beneficial organisms in the same habitat. In addition, detrivores are exposed to crop residues containing the toxin when incorporated into the soil. The current 2-year study (2003, 2004) evaluated effects of two silage-corn varieties: Pioneer var. 38A25 (Bt-corn expressing the Cry1Ab toxin) and Pioneer var. 38A24 (parent isoline) on species diversity and evenness of carabid beetles and Collembola. Pitfall traps were used to collect surface-dwelling species on a bimonthly schedule from April to October. Soil cores were taken once a month from April to October to sample subterranean species, which were extracted using Berlese funnels. All individuals were recorded and identified where possible to species level for analysis in the Simpson's D and Shannon-Wiener H' diversity indices. Evenness was measured using Simpson's E', after which dominant species were analyzed in a multivariate ordination analysis. Results showed Bt-corn had no negative effects on any of the organisms analyzed. There was a significant year effect on the abundance of surface-dwelling Collembola and on species diversity of soil-dwelling Collembola. Our findings suggest that crop management practices and/or environmental conditions (e.g., heavy rainfall during the 2004 growing season) had the greatest impact on species diversity and evenness, rather than the crop itself (Bt or isoline).

Impact of insecticide treatments on Ostrinia nubilalis (Hübner) (Lepidoptera: Crambidae) and their influence on the mycotoxin contamination of maize kernels

European corn borer (ECB), Ostrinia nubilalis (Hübner), is the main maize pest in Central and Southern Europe and promotes the infection of maize with Fusarium spp., which produce mycotoxins. The objective of this study was to determine the effect of insecticide treatments on ECB damage, Fusarium infection and mycotoxin contamination. The field experiments were performed from 2000 to 2006 in three locations in north-western Italy. At harvest, ears were rated for the incidence and severity of ECB damage and Fusarium ear rot symptoms, and the harvested kernels were analysed for fumonisins and zearalenone. In all the years except 2003, the chemical treatment had a significant effect on ECB incidence and severity. The ear damage was reduced, on average, by 44.1%. Fusarium ear rot and fumonisin contamination were affected by ECB control. The occurrence of the mycotoxin was significantly reduced, on average by 68%. The differences between the treatments were less clear in the year with highest ECB pressure. No significant difference was observed between the different insecticide classes. No relations were detected between the ECB activity and the occurrence of zearalenone. This research indicates that the production of kernels with low fumonisin content may be enhanced by an insecticide treatment against the second ECB generation.

Monitoring of European Corn Borer with Pheromone-Baited Traps: Review of Trapping System Basics and Remaining Problems

Since the identification of female European corn borer, Ostrinia nubilalis (Hübner) pheromone, pheromone-baited traps have been regarded as a promising tool to monitor populations of this pest. This article reviews the literature produced on this topic since the 1970s. Its aim is to provide extension entomologists and other researchers with all the necessary information to establish an efficient trapping procedure for this moth. The different pheromone races of the European corn borer are described, and research results relating to the optimization of pheromone blend, pheromone bait, trap design, and trap placement are summarized followed by a state-of-the-art summary of data comparing blacklight trap and pheromone-baited trap techniques to monitor European corn borer flight. Finally, we identify the information required to definitively validate/invalidate the pheromone-baited traps as an efficient decision support tool in European corn borer control.

Monitoring of European Corn Borer with Pheromone-Baited Traps: Review of Trapping System Basics and Remaining Problems

Since the identification of female European corn borer, Ostrinia nubilalis (Hübner) pheromone, pheromone-baited traps have been regarded as a promising tool to monitor populations of this pest. This article reviews the literature produced on this topic since the 1970s. Its aim is to provide extension entomologists and other researchers with all the necessary information to establish an efficient trapping procedure for this moth. The different pheromone races of the European corn borer are described, and research results relating to the optimization of pheromone blend, pheromone bait, trap design, and trap placement are summarized followed by a state-of-the-art summary of data comparing blacklight trap and pheromone-baited trap techniques to monitor European corn borer flight. Finally, we identify the information required to definitively validate/invalidate the pheromone-baited traps as an efficient decision support tool in European corn borer control.

Large‐scale releases of Trichogramma ostriniae to suppress Ostrinia nubilalis in commercially grown processing and fresh market sweet corn

Abstract: We evaluated the egg parasitoid Trichogramma ostriniae (Pang et Chen) (Hym.: Trichogrammatidae) for control of European corn borer [Lep.:Crambidae: Ostrinia nubilalis (Hübner)] in fields of commercial processing sweet corn in New York in 2002 and 2003. We made inoculative releases of 75 000 T. ostriniae/ha when corn was at mid‐whorl and regional O. nubilalis activity had begun. Each release field was paired with a similar non‐release control. The incidence of egg mass parasitism, number of stalk tunnels, incidence of ear damage and effect on insecticide spray decisions were evaluated. Parasitism of cumulative number of O. nubilalis egg masses was 51.3 ± 7.2% and 43.5 ± 5.7% (mean ± SEM) in release fields in 2002 and 2003 respectively. The incidence of ear damage by O. nubilalis was not affected by T. ostriniae in either year of the study. There was no difference in stalk damage between release fields and control fields in either 2002 or 2003. However, individual comparisons between paired release and control fields showed reduced stalk tunnelling in 10 of 19 fields, but ear damage was reduced in only two of 19 fields. Neither the number of actual insecticide sprays nor the number of decisions to spray based on sequential sampling were affected significantly by releasing T. ostriniae. In a separate but related study, where releases were conducted in commercial fresh market sweet corn and used higher rates of release, T. ostriniae had no effect on the number of insecticidal sprays. In an additional experiment using small plots of sweet corn, ear damage was similar whether plots were treated with T. Ostriniae or with insecticide. Additional research should focus on improving the timing, frequency and rate of releases.

Integrating Biological and Chemical Controls in Decision Making: European Corn Borer (Lepidoptera: Crambidae) Control in Sweet Corn as an Example

As growers switch to transgenic crops and selective insecticides that are less toxic to natural enemies, natural enemies can become more important in agricultural pest management. Current decision-making guides are generally based on pest abundance and do not address pest and natural enemy toxicity differences among insecticides or the impact of natural enemies on pest survival. A refined approach to making pest management decisions is to include the impact of natural enemies and insecticides, thereby better integrating biological and chemical control. The result of this integration is a dynamic threshold that varies for each product and the level of biological control expected. To demonstrate the significance of conserved biological control in commercial production, a decision-making guide was developed that evaluates control options for European corn borer, Ostrinia nubilalis (Hübner) (Lepidoptera: Crambidae), in sweet corn, Zea mays L., where the primary natural enemies are generalist predators. Management options are lambda-cyhalothrin (broad-spectrum insecticide), spinosad (selective insecticide), Trichogramma ostriniae (Peng and Chen) (Hymenoptera: Trichogrammatidae) (parasitoid), and Bacillus thuringiensis (Bt) sweet corn (transgenic variety). The key factors influencing thresholds for all treatments are the intended market, predator populations, and the presence of alternative foods for the predators. Treatment cost is the primary factor separating the threshold for each treatment within a common scenario, with the lowest cost treatment having the lowest pest threshold. However, when the impact of a treatment on natural enemies is projected over the 3-wk control period, the impact of the treatment on predators becomes the key factor in determining the threshold, so the lowest thresholds are for broad-spectrum treatments, whereas selective products can have thresholds > 6 times higher by the third week. This decision guide can serve as a framework to help focus future integrated pest management research and to aid in the selection of pest management tools.

Integrating Biological and Chemical Controls in Decision Making: European Corn Borer (Lepidoptera: Crambidae) Control in Sweet Corn as an Example

Integrating Biological and Chemical Controls in Decision Making: European Corn Borer (Lepidoptera: Crambidae) Control in Sweet Corn as an Example

(27) Effect of Plant Stand Density and Pesticide Application Technology on Insect Pests and Diseases of Bell Peppers

The impact of pesticide application technology and crop stand density on bell pepper production was evaluated in a series of field trials, during 2004 and 2005, at the North Central Agricultural Research Station, Fremont, Ohio. In 2004, one trial tested three sprayers, at a speed of 8 and 4 mph, using insecticides at half the recommended rate and one treatment at full rate. Sprayers evaluated included an air-assisted electrostatic sprayer, a Cagle sprayer equipped with AI-11005 or AI-110025 nozzles, and an air-blast sprayer with XR-1003-VS or XR-110015-VS nozzles. In 2005, one experiment tested the interaction of two application technologies, three planting distances within row, and single vs. twin rows. Another experiment compared the Cagle sprayer (with TJ60-11003 or AI-110025 nozzles) and the airblast sprayer (with XR-110015-VS nozzles), at a speed of 4 mph, and insecticides at half the recommended rate. In 2004, the Cagle sprayer with air-induction nozzle, half rate, at 8 mph obtained the highest fruit yield. There was not significant improvement in European corn borer control by applying insecticides at full rate with the Cagle sprayer and all treatments achieved significantly better bacterial soft rot control than the untreated control. In 2005, the trials were terminated early due to crop destruction by Phytophthora capsici. Red fruit weighed less at high than at medium or low plant stand densities. Clean yield of red fruit was significantly greater in single rows than in twin rows. Marketable yield of green fruit was greater using the TJ60-11003 than using the AI-110025 nozzles.

Host–Parasitoid Interactions in a Transgenic Landscape: Spatial Proximity Effects of Host Density

Widespread management practices such as transgenic insecticidal crops influence the distribution and density of targeted pest species across the agricultural landscape. Natural enemies must cope with this altered distribution, and their response potentially influences the rate of resistance evolution in the pest. The purpose of this study was to examine spatial patterns of parasitism by the specialist parasitoid Macrocentrus grandii Goidanich (Hymenoptera: Braconidae) in response to the density of its host, the European corn borer (Ostrinia nubilalis Hubner [Lepidoptera: Crambidae]). When we manipulated host distribution and observed resulting patterns of wasp density and parasitism, we found that the smallest host aggregations had the lowest parasitism, but only when not associated with larger host aggregations. A subsequent field experiment confirmed that proximity to large host aggregations increased parasitism in small host aggregations. Theory indicates that such positive density-dependent parasitism should accelerate the evolution of toxin resistance in pest species, but our study suggests that close spatial proximity between insecticidal crops and refuges may help equalize M. grandii parasitism and that simple management techniques such as in-field refuges could potentially increase the complementarity of transgenic and biological control of European corn borer in this system. Further research is needed, however, before extrapolating the results of our small-scale study to field-level patterns and concluding that M. grandii will necessarily hasten resistance evolution in the European corn borer.

Alternative Agents for Control of European Corn Borer and Corn Flea Beetle on Sweet Corn

ABSTRACT Small plot field trials were conducted in 2002 and 2003 to compare European corn borer (ECB) (Ostrinia nubilalisHübner) control using currently recommended insecticides, carbofuran (FURADAN® 480F) and lambda-cyhalothrin (MATADOR® 120EC), with spinosad (SUCCESS® 480SC) and Bt-sweet corn (ATTRIBUTE®). In both years, foliar applications of spinosad, lambda-cyhalothrin or carbofuran, or Bt-sweet corn significantly reduced the number of ECB stalk tunnels, percent damaged plants and number of damaged kernels, tunnels and larvae on ears at harvest compared to the untreated control. More marketable ears were harvested from plots treated with the insecticides and Bt-sweet corn treatments than from untreated controls. Small plot field trials also were conducted to investigate the efficacy against corn flea beetle (CFB) (Chaetocnema pulicaria Melsheimer) of the seed treatment insecticides, imidacloprid (GAUCHO® 480FS) and clothianidin (PONCHO® 600F). Imidacloprid was evaluated in both 2002 and 2003, clothianidin in 2003 only. Seed treatment with either insecticide significantly reduced numbers of CFB feeding damage marks compared to untreated controls. Clothianidin provided more effective control of CFB than imidacloprid. Overall, the results demonstrated that spinosad or Bt-sweet corn provided ECB control comparable to carbofuran and lambda-cyhalothrin, while imidacloprid or clothianidin seed treatments reduced sweet corn seedling injury from CFB.

Evaluation of Detection Methods for Genetically Modified Traits in Genotypes Resistant to European Corn Borer and Herbicides

Detection of genetically modified (GM) traits in corn (Zea mays L.) is urgently needed for preservation of genetic identity and marketing GM products. A laboratory study was conducted to evaluate the efficiency, accuracy, and reliability of different analytical methods to detect GM traits in corn. Samples with known fractions of GM concentrations (Bacillus thuringiensis [Bt], Liberty Link [LL] and stacked [Bt/LL] genes) from commercial seed companies and those derived from yellow kernels in a white corn ear, outcrossed by pollen of neighboring Bt hybrid, were tested by lateral flow quick test kits and by enzyme-linked immunosorbent assay (ELISA)-based test strips purchased from different companies. Liberty Link hybrids are resistant to glufosinate (Liberty or Basta) herbicides, whereas Bt corn is developed for the control of European corn borer (Ostrinia nubilalis). Selected samples of GM concentrations were also tested in a commercial laboratory using DNA-based polymerase chain reaction (PCR) test. The results demonstrated that qualitative lateral flow quick tests could detect samples containing 1% or higher Bt and 2% or higher LL concentrations within the recommended time limit of the test. Faint test lines for samples containing 0.5 to 1% Bt or 1 to 2% LL concentrations appeared if samples remained in the test cup overnight. ELISA test strips detected the Bt content semiquantitatively in the range of 0.5 to 2.0%. Grain samples derived from non-Bt corn outcrossed by neighboring Bt pollen had usually lower GM concentrations than commercial GM seed samples. Both ELISA- and DNA-based PCR tests distinguished samples with GM concentrations between 0.1 to 0.5%, but the precision of quantification at this range was very low and results were highly inconsistent.