Abundance Of Nontarget Arthropods Research Articles

Impact of Transgenic Cry1Ab/2Aj Maize on Abundance of Non-Target Arthropods in the Field.

Transgenic Bacillus thuringiensis (Bt) maize has broad prospects for application in China. Before commercialization, it is necessary to assess possible ecological impacts, including impacts on non-target arthropods (NTAs) in the field. In the present study, transgenic Bt maize expressing cry1Ab/2Aj and its corresponding non-transformed near isoline were planted under the same environmental and agricultural conditions, and arthropods in the field were collected during the three main growth stages of maize. In a one year trial, the results showed the composition of NTA communities in the transgenic and control maize fields were similar. There were no significant differences for community-level parameters of species richness (S), Shannon–Wiener diversity index (H′), evenness index (J) and Simpson’s dominant concentration (C) between the two types of maize fields. Likewise, a Bray–Curtis dissimilarity and distance analysis showed that Cry1Ab/2Aj toxin exposure did not increase community dissimilarities between Bt and non-Bt maize plots and that the structure of the NTAs community was similar on the two maize varieties. Furthermore, planting of the transgenic cry1Ab/2Aj maize did not affect the density or composition of non-target decomposers, herbivores, predators, parasitoids and pollinator guilds. In summary, our results showed that planting of Bt maize producing Cry1Ab/Cry2Aj proteins do not adversely affect population dynamics and diversity of NTAs.

The impact of bioinsecticide overdoses of Beauveria bassiana on species diversity and abundance of not targeted arthropods in South Sumatra (Indonesia) freshwater swamp paddy

Abstract. Hanif KI, Herlinda S, Irsan C, Pujiastuti Y, Prabawati G, Hasbi, Karenina T. 2020. The impact of bioinsecticide overdoses of Beauveria bassiana on species diversity and abundance of not targeted arthropods in South Sumatra (Indonesia) freshwater swamp paddy. Biodiversitas 21: 2124-2136. Bioinsecticides have been shown to reduce insect pest populations, but it is necessary to monitor the effect of bioinsecticide overdoses on non-target arthropods because they are abundant in rice fields. This study aimed to analyze the impact of bioinsecticide overdoses of B. bassiana on species diversity and abundance of non-target arthropods. Bioinsecticides derived from Beauveria bassiana were sprayed on the paddy every two weeks until the ripening stage, at a dose of 1, 2, 3, 4 L.ha-1, control (without insecticide), and abamectin as prescribed. The abundance of spiders and predatory arthropods did not decrease when bioinsecticides were applied but the abundance of spiders, especially Lycosidae and Salticidae dropped significantly when abamectin was applied. The abundance of the parasitoid decreased significantly when abamectin was applied, but the abundance of parasitoids applied by bioinsecticide was not significantly different from those of control. The abundance of insect pests started to decrease when bioinsecticide was applied to 2, 3 or 4 L.ha-1. The diversity species of non-target arthropods (spiders, predatory arthropods, and parasitoids) tended to decrease when it was applied bioinsecticides 3 and 4 L.ha-1 or abamectin, but their abundance remained high and no species dominance was found. For this reason, the correct dosage for suppressing insect pests abundance by not decreasing the abundance and diversity of non-target species is 2 L.ha-1 and applied when herbivore abundance is high.

The tick biocontrol agent Metarhizium brunneum (= M. anisopliae) (strain F52) does not reduce non-target arthropods.

Previous studies have found that Met52®, which contains the entomopathogenic fungus Metarhizium brunneum, is effective in reducing the abundance of Ixodes scapularis, the tick vector for the bacterium causing Lyme disease and for other tick-borne pathogens. Given widespread interest in effective, safe methods for controlling ticks, Met52 has the potential to be used at increasing scales. The non-target impacts of Met52, as applied for tick control, have not yet been assessed. A Before-After-Control-Impact experiment was conducted to assess the effects of Met52 on non-target arthropods in lawn and forest habitats typical of residential yards. Ground-dwelling arthropods were collected using bulk sampling of soil and litter, and pitfall sampling. Arthropods were sampled once before and twice after treatment of plots with either Met52 or water (control). Multivariate general linear models were used to jointly model the abundance of arthropod orders. For each sampling method and post-spray sampling occasion, Akaike Information Criterion values were used to compare the fits of two alternative models: one that included effects of period (before vs. after spray), habitat (lawn vs. forest), and treatment (Met52 vs. control), versus a nested null model that included effects of period, and habitat, but no treatment effect. The null model was consistently better supported by the data. Significant effects were found of period and habitat but not treatment. Retrospective power analysis indicated the study had 80% power to detect a 50% reduction in arthropod abundance, as measured by bulk samples taken before versus one week after treatment. The deployment of Met52 in suburban settings is unlikely to cause meaningful reductions in the abundance of non-target arthropods.

Assessment of the effects of transgenic Bt cotton Bollgard II on the abundance of nontarget arthropods in Burkina Faso

Abstract The effect of transgenic cotton Bollgard II on the abundance of nontarget arthropods was assessed under field conditions in three areas in Burkina Faso for four successive years (2010–2013). The experiment was carried out on two 0.5‐ha plots of which one was seeded with the Bollgard II and one with the non‐Bacillus thuringiensis Berliner (Bt) isogenic cultivar. Over four collection methods [plastic bagging (28 collections), water trap (28 collections), beat cloth (six collections) and pitfall traps (six collections)] and 4 years, no statistically significant differences were detected between Bollgard II and the conventional control for 45 out of 48 comparisons. Differences detected were rather random and not consistently detected across collection methods, sites and/or years. Thus, these differences were not indicative of a consistent response associated with the trait and are not considered biologically meaningful in terms of an adverse environmental impact (nontarget arthropod abundance) of Bollgard II compared to conventional cotton receiving six insecticide sprays.

Three-Year Field Monitoring of Cry1F, Event DAS-Ø15Ø7–1, Maize Hybrids for Nontarget Arthropod Effects

Field studies were conducted over a 3-yr period to investigate the potential effects of cultivating transgenic maize hybrids containing a Cry1F insect-resistant protein on nontarget arthropod abundance. The narrow spectrum of activity of Cry1F against a subset of lepidopteran pest species would not suggest broad-spectrum effects on nontarget arthropods. However, because of the insecticidal nature of Bt proteins, an alternate hypothesis is that some nontargets may be affected by exposure to the protein. To examine this hypothesis at the field level, monitoring for nontarget organism abundance was initiated at four locations across the U.S. Corn Belt from 2004 through 2006. At each location, paired fields (approximately 0.8 ha each) of commercial Cry1F maize hybrids and isogenic nontransgenic control hybrids were planted. Sampling methods used to monitor nontarget organisms included visual surveillance, sticky cards, pitfall traps, and litterbags. Data were analyzed using multivariate analyses to look for a general community level response to the treatments. Analysis of variance was conducted on individual taxa to detect differences distinct from the primary community response. Community level analyses of the nontarget arthropod abundance showed no significant impact on community abundance when comparing Bt with non-Bt maize fields. Analyses of the individual taxa also showed no significant differences in abundance between Bt and non-Bt fields. Results of these studies confirm earlier laboratory testing and support the hypothesis that Cry1F maize does not produce adverse effects on nontarget arthropods occurring in maize fields.

Selection of Nontarget Arthropod Taxa for Field Research on Transgenic Insecticidal Crops: Using Empirical Data and Statistical Power

One of the possible adverse effects of transgenic insecticidal crops is the unintended decline in the abundance of nontarget arthropods. Field trials designed to evaluate potential nontarget effects can be more complex than expected because decisions to conduct field trials and the selection of taxa to include are not always guided by the results of laboratory tests. Also, recent studies emphasize the potential for indirect effects (adverse impacts to nontarget arthropods without feeding directly on plant tissues), which are difficult to predict because of interactions among nontarget arthropods, target pests, and transgenic crops. As a consequence, field studies may attempt to monitor expansive lists of arthropod taxa, making the design of such broad studies more difficult and reducing the likelihood of detecting any negative effects that might be present. To improve the taxonomic focus and statistical rigor of future studies, existing field data and corresponding power analysis may provide useful guidance. Analysis of control data from several nontarget field trials using repeated-measures designs suggests that while detection of small effects may require considerable increases in replication, there are taxa from different ecological roles that are sampled effectively using standard methods. The use of statistical power to guide selection of taxa for nontarget trials reflects scientists' inability to predict the complex interactions among arthropod taxa, particularly when laboratory trials fail to provide guidance on which groups are more likely to be affected. However, scientists still may exercise judgment, including taxa that are not included in or supported by power analyses.

Effects of Insecticide-Treated and Lepidopteran-Active <I>Bt</I> Transgenic Sweet Corn on the Abundance and Diversity of Arthropods

A field study was conducted over 2 yr to determine the effects of transgenic sweet corn containing a gene from the bacterium Bacillus thuringiensis (Bt) on the diversity and abundance of nontarget arthropods. The Bt hybrid (expressing Cry1Ab endotoxin for lepidopteran control) was compared with near-isogenic non-Bt and Bt hybrids treated with a foliar insecticide and with a near-isogenic non-Bt hybrid without insecticides. Plant inspections, sticky cards, and pitfall traps were used to sample a total of 573,672 arthropods, representing 128 taxonomic groups in 95 families and 18 orders. Overall biodiversity and community-level responses were not significantly affected by the transgenic hybrid. The Bt hybrid also had no significant adverse effects on population densities of specific nontarget herbivores, decomposers, and natural enemies enumerated at the family level during the crop cycle. As expected, the insecticide lambda-cyhalothrin had broad negative impacts on the abundance of many nontarget arthropods. One insecticide application in the Bt plots reduced the overall abundance of the natural enemy community by 21-48%. Five applications in the non-Bt plots reduced natural enemy communities by 33-70%. Nontarget communities affected in the insecticide-treated Bt plots exhibited some recovery, but communities exposed to five applications showed no trends toward recovery during the crop cycle. This study clearly showed that the nontarget effects of Bt transgenic sweet corn on natural enemies and other arthropods were minimal and far less than the community-level disruptions caused by lambda-cyhalothrin.

Nontarget Effects of Transgenic Insecticidal Crops: Implications of Source-Sink Population Dynamics

Widespread planting of transgenic insecticidal (TI) crops for pest control has raised concerns about potential harm to nontarget arthropods. Because the first generation of TI crops produce single Bacillus thuringiensis (Bt) toxins causing little or no harm to most nontarget arthropods, they are not likely to cause such negative effects. However, varieties of transgenic crops with multiple Bt toxins or novel toxins might be more harmful to nontarget arthropods. Field studies assessing nontarget effects typically compare the relative abundance of nontarget arthropods in TI crop fields to non-TI crop fields. However, for nontarget arthropods that are killed by TI crops, such analyses may miss important effects. Results from simulations of a spatially explicit population dynamics model show that large-scale planting of TI crops could cause three types of negative effects on nontarget arthropods that suffer mortality caused by TI crops: (1) lower abundance in TI fields than non-TI fields with little or no effect on abundance in non-TI fields, (2) lower abundance in TI fields than non-TI fields and decreased abundance in non-TI fields, and (3) loss of the arthropod from TI and non-TI fields. Simulation results show that factors increasing the potential for negative effects of TI crops on nontarget arthropods in non-TI fields are low reproduction, high emigration, high adoption of TI crops, high mortality in TI fields, insecticide sprays, and rotation of TI and non-TI fields. The results suggest that risk assessment should consider the regional distribution of transgenic crops and the life history traits of nontarget arthropods to identify the most vulnerable regions and nontarget species.

Assessing the Effects of Pest Management on Nontarget Arthropods: The Influence of Plot Size and Isolation

Evaluations of field research on the nontarget effects of pest management, particularly the production of transgenic crops with insecticidal properties, suggest the methods used are sometimes unlikely to detect real differences among treatments. Among potential problems, abundance estimates may be scale-dependent for many arthropods, which move among experimental plots and between experimental plots and the surrounding environment. Insecticide-disturbed plots of field corn in a range of sizes in 2003 (0.03–0.53 ha; 18–72 m wide) and 2004 (0.01–0.13 ha; 9–36 m wide) were used for testing effects of scale on nontarget arthropod abundance. Possible effects of artificially isolating plots by removal of vegetation around plot borders were also studied in 2003. Community and taxon-based analyses showed abundance of foliar (aboveground) arthropods depended on plot size and isolation. While abundance of foliar arthropods was generally greater in smaller plots, isolation treatments suggested some taxa may have been either repelled or attracted to isolated plots. Levels of some epigeal (ground-dwelling) taxa were also size or isolation-dependent, but community-based analysis did not indicate a strong collective response to treatments. Recommendation of a practical but rigorous minimum plot size for nontarget studies may not be appropriate because responses to plot size varied among taxa. However, because arthropod movement into and out of plots can reduce differences between treatments, results suggest the use of small plots (width <9 m) for nontarget studies on transgenic crops generally should be avoided. Similarly, the taxon-specific effects of isolating plots should be considered when planning studies or interpreting results.

Assessing the Effects of Pest Management on Nontarget Arthropods: The Influence of Plot Size and Isolation

Evaluations of field research on the nontarget effects of pest management, particularly the production of transgenic crops with insecticidal properties, suggest the methods used are sometimes unlikely to detect real differences among treatments. Among potential problems, abundance estimates may be scale-dependent for many arthropods, which move among experimental plots and between experimental plots and the surrounding environment. Insecticide-disturbed plots of field corn in a range of sizes in 2003 (0.03–0.53 ha; 18–72 m wide) and 2004 (0.01–0.13 ha; 9–36 m wide) were used for testing effects of scale on nontarget arthropod abundance. Possible effects of artificially isolating plots by removal of vegetation around plot borders were also studied in 2003. Community and taxon-based analyses showed abundance of foliar (aboveground) arthropods depended on plot size and isolation. While abundance of foliar arthropods was generally greater in smaller plots, isolation treatments suggested some taxa may have been either repelled or attracted to isolated plots. Levels of some epigeal (ground-dwelling) taxa were also size or isolation-dependent, but community-based analysis did not indicate a strong collective response to treatments. Recommendation of a practical but rigorous minimum plot size for nontarget studies may not be appropriate because responses to plot size varied among taxa. However, because arthropod movement into and out of plots can reduce differences between treatments, results suggest the use of small plots (width <9 m) for nontarget studies on transgenic crops generally should be avoided. Similarly, the taxon-specific effects of isolating plots should be considered when planning studies or interpreting results.

Select Nontarget Arthropod Abundance in Transgenic and Nontransgenic Field Crops in Ohio

Nontarget arthropod populations were monitored in both transgenic and nontransgenic corn and soybean fields in western and central Ohio. A total of 24 fields, 12 corn and 12 soybean, were inspected weekly from late June through mid August. Half of the cornfields were Bacillus thuringiensis (Bt) hybrids and half of the soybean fields were Roundup Ready (RR). Sweep net samples in soybean fields and unbaited Pherocon AM yellow sticky traps in both soybean and cornfields were used to collect nontarget arthropods. Soil samples were also taken from all 24 fields to compare soil mite populations. A select group of 15 readily identifiable arthropods composed mainly of beneficial insects commonly found in field crops, were recorded in weekly sweep net and sticky trap samples for later analysis. Sweep net data from soybean fields revealed no significant differences in nontarget arthropods. Yellow sticky trap data from soybean and corn fields found significantly more green lacewing adults (Chrysopa spp.) in six pooled non-RR soybean fields, significantly more rove beetles in one non-Bt cornfield, and significantly more Orius spp. in one Bt cornfield. There were also significantly more soil inhabiting mites at one non-RR soybean field. Based on the abundance of these arthropod populations in paired transgenic and nontransgenic fields, few negative effects on the 15 nontarget arthropods selected can be directly associated with transgenic soybean and corn crops in Ohio.

Ostrinia nubilalisparasitism and the field abundance of non-target insects in transgenicBacillus thuringiensiscorn (Zea mays)

In this study, we evaluated in field trials the effects on non-target species, of transgenic corn producing the Cry1Ab toxin of Bacillus thuringiensis (Bt). In 1998, we collected Ostrinia nubilalis (Hübner) larvae from transgenic Bt corn (Novartis Hybrid 176) and non-Bt corn at four geographical sites. We found a significant variation in parasitism by the tachinids Lydella thompsoni (Herting) and Pseudoperichaeta nigrolineata (Walker) among sites, and more parasitism in non-Bt than in Bt fields. The Bt effect did not vary significantly among fields. In 1999, we performed a field experiment at two sites, comparing the temporal abundance of non-target arthropods in Bt corn (Monsanto Hybrid MON810) and non-Bt corn. The non-target insects studied included the aphids Metopolophium dirhodum (Walker), Rhopalosiphum padi (L.) and Sitobion avenae (F.), the bug Orius insidiosus (Say), the syrphid Syrphus corollae (Meigen), the ladybird Coccinella septempunctata (L.), the lacewing Chrysoperla carnea (Stephens), thrips and hymenopteran parasitoids. For all species but one, the number of individuals varied greatly over the season but did not differ between the types of corn. The only exception was thrips which, at one site, was significantly more abundant in Bt corn than in non-Bt corn. However this difference did not remain significant when we took the multiple tests into account. Implications for pest resistance management, population dynamics and risk assessment are discussed.

Effects of gypsy moth suppression tactics on litter- and ground-dwelling arthropods in the central hardwood forests of the Cumberland Plateau

Abstract This study assessed the impact of three gypsy moth suppression tactics on non-target arthropod abundance in the mixed mesophytic forests of the Cumberland Plateau prior to gypsy moth establishment in the region. Abundance of litter- and ground-dwelling arthropods was assessed in areas receiving applications of reduced rates of diflubenzuron and Bacillus thuringiensis var. kurstaki, simulating gypsy moth suppression programs, and compared to untreated controls, simulating a hands-off management approach. Study plots in southeastern Kentucky were aerially sprayed one time in May of 1997; control plots received no insecticide. In 1997 and 1998 we sampled arthropods in strata ranging from ground level to the forest canopy. Here we report the effects of the treatments on ground- and litter-dwelling arthropods. Gypsy moth suppression tactics negatively impacted litter-dwelling mites and thrips, with populations in diflubenzuron-treated plots significantly lower relative to untreated controls in the year of application. The abundance of predatory spiders and rove beetles was also affected by treatment applications. Treatment effects were evident 1 year post-application for populations of thrips, spiders, bark/ambrosia beetles, millipedes, and centipedes. The highly clustered distribution patterns of many arthropods, as well as variable weather patterns, may have confounded the effects of our treatments. Since the gypsy moth is not yet established in the region, results of this study will be useful to land owners and natural resource managers to enable them to make well-informed decisions regarding future gypsy moth infestations.

Effects of pyriproxyfen spray, powder, and oral bait treatments on the relative abundance of nontarget arthropods of black-tailed prairie dog (Rodentia: Sciuridae) towns.

Separate black-tailed prairie dog, Cynomys ludovicianus (Ord), towns on the Rocky Mountain Arsenal National Wildlife Refuge, Colorado, were treated with technical pyriproxyfen (Nylar) spray, powder, and oral bait. The treatments were applied to reduce relative abundance of the plague vector Oropsylla hirsuta (Baker). Because pyriproxyfen is a juvenile hormone analog, we were also concerned with the effects of the treatments on nontarget arthropods, which is the focus of this study. Pitfall traps and sweep net sampling were used to measure relative abundance of arthropod populations pre- and posttreatment. Nontarget arthropod sampling produced a large number of statistical comparisons that indicated significant declines (P < 0.05) in relative arthropod abundance. Many of the significant declines were probably because of natural fluctuations in arthropod populations rather than treatment effects. Because arthropod populations appeared to fluctuate randomly, we only made inferences about highly significant (P < 0.001) declines. In doing so, we hoped to abate some of the confusion created by the natural fluctuation in arthropod abundance and increase our chance of correctly attributing a population reduction to a treatment effect. Only Homoptera at the pyriproxyfen powder site exhibited highly significant reductions that appeared to be attributed to the treatments. Pyriproxyfen spray treatments did not significantly reduce relative arthropod abundance.

Reduced agent-area treatments (RAAT) for management of rangeland grasshoppers: Efficacy and economics under operational conditions

The Reduced Agent-Area Treatment (RAAT) approach involves applying low rates of insecticides in intermittent swaths to control grasshopper infestations in an effort to achieve a more economically and environmentally sound pest management strategy compared to traditional blanket applications at high rates. Operationalscale (>250 ha) insecticide tests on Wyoming rangeland grasshopper infestations (18-56 grasshoppers/m2) at two sites in 1997 revealed that carbaryl yielded 94% control as a blanket treatment (560 g/ha) and 81% control as a RAAT application (280 g/ha applied to 50% of the infested land). Malathion yielded 90% control as a blanket treatment (683 g/ha) and 91% control as an RAAT application (342 g/ha applied to 80% of the infested land), and fipronil (4 g/ha) yielded 98% control as a blanket treatment and 92% control when applied to 33% of the infested land. One year after treatment, the RAAT and blanket-treated plots had 2-4% (Pollet Ranch) of the densities in untreated plots. Economic analysis showed that the greatest benefit:cost ratio was obtained with the fipronil-RAAT method, followed by carbaryl-RAAT, malathion-RAAT, malathion-blanket, fipronil-blanket, carbaryl-blanket. The worst-case outcome of fipronil and carbaryl with a RAAT approach had a greater economic return than the best-case outcome of no treatment. Following blanket treatments, non-target arthropod abundance was highest in the fipronil plots, followed by carbaryl and malathion; arthropod biomass was higher in the carbaryl plots than fipronil and malathion. In RAAT plots, arthropods were generally less impacted than in the blanket plots, with the least reduction caused by fipronil and carbaryl. Thus, the RAAT tactic appears to be economically and environmentally superior to blanket treatments under large-scale, operational conditions.

Evaluation of Possible Nonlethal Side Effects of Permethrin Used in Predator Exclusion Experiments to Evaluate Amblyseius limonicus (Acari: Phytoseiidae) in Biological Control of Cassava Mites (Acari: Tetranychidae)

Permethrin has been recommended for use in predator exclusion studies of Amblyseius limonicus Garman & McGregor (formerly in Typhlodromalus), an important predator of tetranychid cassava (Manihot esculenta Crantz) pests: green mite, Mononychellus progresivus Doreste, and twospotted spider mite, Tetranychus urticae Koch. Among criteria for a chemical exclusion agent are selective toxicity and lack of side effects such as enhanced pest fecundity, stimluation of plant growth, or improvement of host plant nutritional quality. Laboratory and field tests provided no evidence for phytostimulation, change in cassava nutritional quality, or increased spider mite fecundity; however, abundance of nontarget arthropods was significantly reduced in permethrin-treated field plots. A possible repellency effect of permethrin on M. progresivus was suggested under laboratory conditions. Implications of repellency and lowered abundance of nontarget species for field use of permethrin as a predator exclusion agent are discussed.