Brian Nault
Cornell University, Entomology, Faculty Member
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<p>Average lethal concentration responses of <i>L</i>. <i>decemlineata</i> populations to imidacloprid compared to frequency of potato production in bioassay collection fields (N = 50 populations). Years of... more
<p>Average lethal concentration responses of <i>L</i>. <i>decemlineata</i> populations to imidacloprid compared to frequency of potato production in bioassay collection fields (N = 50 populations). Years of potato production indicate the number of potato crops grown during the four years preceding the bioassay year. Error bars represent 95% confidence intervals of the mean. Numbers in parentheses represent the count of fields in each group.</p
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<p><sup>a</sup> Parameter estimate differs significantly from zero (*, <i>P</i> < 0.05)</p><p><sup>b</sup> Proportion potato grown on available cropland in the year bioassays were... more
<p><sup>a</sup> Parameter estimate differs significantly from zero (*, <i>P</i> < 0.05)</p><p><sup>b</sup> Proportion potato grown on available cropland in the year bioassays were conducted</p><p><sup>c</sup> Proportion cultivated cropland where potato was grown at least once in the four years preceding the bioassay</p><p><sup>d</sup> Represents the interaction between specified model parameter and state</p><p>Parameter estimates (±SE), AIC and difference in AIC from best models fitting log transformed LC<sub>50</sub> estimates of resistance in <i>L</i>. <i>decemlineata</i> populations.</p
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<p>Potato incidence on cultivated cropland over four consecutive years of prior production estimated from within a 1.5 km radius surrounding each sample field centroid (N = 50 fields). Frequency of production shows that farmers... more
<p>Potato incidence on cultivated cropland over four consecutive years of prior production estimated from within a 1.5 km radius surrounding each sample field centroid (N = 50 fields). Frequency of production shows that farmers often rotate potato at variable time intervals, ranging from low intensity production (potato occurring once in four years) to high intensity production (continuous potato).</p
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As part of an insect resistance management plan to preserve Bt transgenic technology, annual monitoring of target pests is mandated to detect susceptibility changes to Bt toxins. Currently Helicoverpa zea (Boddie) monitoring involves... more
As part of an insect resistance management plan to preserve Bt transgenic technology, annual monitoring of target pests is mandated to detect susceptibility changes to Bt toxins. Currently Helicoverpa zea (Boddie) monitoring involves investigating unexpected injury in Bt crop fields and collecting larvae from non-Bt host plants for laboratory diet bioassays to determine mortality responses to diagnostic concentrations of Bt toxins. To date, this monitoring approach has not detected any significant change from the known range of baseline susceptibility to Bt toxins, yet practical field-evolved resistance in H. zea populations and numerous occurrences of unexpected injury occur in Bt crops. In this study, we implemented a network of 73 sentinel sweet corn trials, spanning 16 U.S. states and 4 Canadian provinces, for monitoring changes in H. zea susceptibility to Cry and Vip3A toxins by measuring differences in ear damage and larval infestations between isogenic pairs of non-Bt and Bt ...
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Biological pest control by natural enemies is an important component of sustainable crop production. Among biological control approaches, natural enemy augmentation is an effective alternative when naturally occurring enemies are not... more
Biological pest control by natural enemies is an important component of sustainable crop production. Among biological control approaches, natural enemy augmentation is an effective alternative when naturally occurring enemies are not sufficiently abundant or effective. However, it remains unknown whether the effectiveness of augmentative biocontrol varies along gradients of landscape composition, and how the interactions with resident enemies may modulate the collective impact on pest suppression. By combining field and lab experiments, we evaluated how landscape composition influenced the effectiveness of predator augmentation, and the consequences on pest abundance, plant damage, and crop biomass. We show for the first time that the effectiveness of predator augmentation is landscape-dependent. In complex landscapes, with less cropland area, predator augmentation increased predation rates, reduced pest abundance and plant damage, and increased crop biomass. By contrast, predator r...
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This file contains the abundance and incidence of insect pest, parasitoid-host ratios, plant damage, and crop yield in cabbage fields located across a gradient of landscape complexity in the Finger lakes region, NY, USA. This data is... more
This file contains the abundance and incidence of insect pest, parasitoid-host ratios, plant damage, and crop yield in cabbage fields located across a gradient of landscape complexity in the Finger lakes region, NY, USA. This data is associated with the publication: Perez-Alvarez R., B. Nault, and K. Poveda. (2018). “Contrasting effects of landscape composition on crop yield mediated by specialist herbivores”. Ecological Applications
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Knowledge of the relative influence of population- versus species-level genetic variation is important to understand patterns of phenotypic variation and ecological relationships that exist among and within morphologically... more
Knowledge of the relative influence of population- versus species-level genetic variation is important to understand patterns of phenotypic variation and ecological relationships that exist among and within morphologically indistinguishable cryptic species and subspecies. In the case of cryptic species groups that are pests, such knowledge is also essential for devising effective population management strategies. The globally important crop pest Thrips tabaci is a taxonomically difficult group of putatively cryptic species. This study examines population genetic structure of T. tabaci and reproductive isolation among lineages of this species complex using microsatellite markers and mitochondrial COI sequences. Overall, genetic structure supports T. tabaci as a cryptic species complex, although limited interbreeding occurs between different clonal groups from the same lineage as well as between individuals from different lineages. These results also provide evidence that thelytoky an...
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ABSTRACT Biological control of pests by natural enemies is dependent not only on local conditions, but also on the surrounding landscape and the interplay between both spatial scales. The intermediate landscape complexity hypothesis... more
ABSTRACT Biological control of pests by natural enemies is dependent not only on local conditions, but also on the surrounding landscape and the interplay between both spatial scales. The intermediate landscape complexity hypothesis states that on farm scale management such as the creation of habitat for natural enemies should be more successful to increase biocontrol services at landscapes of intermediate complexity. However, it is still unclear how augmentative biological control as a local practice is affected by the landscape context and the naturally occurring enemy communities. In this study, we provide empirical evidence of how the effect of augmentative biocontrol by the spined soldier bug, Podisus maculiventris (Hemiptera: Pentatomidae), is influenced by the surrounding landscape. We selected pairs of cabbage fields (one with augmentative biological control and the other unmanaged) along a landscape complexity gradient to determine the effects of augmentative releases on biocontrol levels and consequent plant damage and yield. We also used sentinel preys and surveillance video cameras to identifty the natural enemies that were attacking lepidopteran pest in the field and to determine their efficiency rates. Understanding interactions among natural enemies and landscape complexity will help us develop a sustainable management strategy based on augmentation of a generalist predator to control cabbage pests while maintaining high yields and profits.
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The diversity and abundance of wild insect pollinators have declined in many agricultural landscapes. Whether such declines reduce crop yields, or are mitigated by managed pollinators such as honey bees, is unclear. We found universally... more
The diversity and abundance of wild insect pollinators have declined in many agricultural landscapes. Whether such declines reduce crop yields, or are mitigated by managed pollinators such as honey bees, is unclear. We found universally positive associations of fruit set with flower visitation by wild insects in 41 crop systems worldwide. In contrast, fruit set increased significantly with flower visitation by honey bees in only 14% of the systems surveyed. Overall, wild insects pollinated crops more effectively; an increase in wild insect visitation enhanced fruit set by twice as much as an equivalent increase in honey bee visitation. Visitation by wild insects and honey bees promoted fruit set independently, so pollination by managed honey bees supplemented, rather than substituted for, pollination by wild insects. Our results suggest that new practices for integrated management of both honey bees and diverse wild insect assemblages will enhance global crop yields.
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Many factors directly and indirectly influence pest dynamics in cultivated crops and identifying the suite of factors associated with a pest’s population dynamics is an important component of pest management. Onion maggot, Delia antiqua... more
Many factors directly and indirectly influence pest dynamics in cultivated crops and identifying the suite of factors associated with a pest’s population dynamics is an important component of pest management. Onion maggot, Delia antiqua (Meigen) (Diptera: Anthomyiidae), is a significant pest of onion in temperature regions worldwide. In the Great Lakes region of North America, D. antiqua is the most important early-season pest of onion and causes considerable damage by killing plants. Despite growers employing the same management and cultivation practices, plant damage by D. antiqua across the region is highly variable. The commonality of production and management suggests that other factors may be important in explaining the disparities in damage across the region, and previous studies have indicated that temperature and precipitation, soil organic matter, surrounding landscape composition, planting date, and plant size at peak fly activity are all important factors affecting D. an...