Like Parents, Like Offspring? Susceptibility to Bt Toxins, Development on Dual-Gene Bt Cotton, and Parental Effect of Cry1Ac on a Nontarget Lepidopteran Pest

2020 ◽  
Vol 113 (3) ◽  
pp. 1234-1242 ◽  
Author(s):  
Marcelo M Rabelo ◽  
João Marcus L Matos ◽  
Silvana M Orozco-Restrepo ◽  
Silvana V Paula-Moraes ◽  
Eliseu José G Pereira
Keyword(s):  
Pest Management ◽  
Larval Mortality ◽  
Parental Effects ◽  
Bt Cotton ◽  
Pest Species ◽  
Larval Weight ◽  
Parental Effect ◽  
Cry Toxins ◽  
Bt Crops ◽  
Bt Toxins

Abstract An important step to devise appropriate pest management strategies for armyworms (Lepidoptera: Noctuidae) in Bacillus thuringiensis Berliner (Bt) crops is to determine the lethal, sublethal, and parental effects of Bt toxins on target and nontarget pest species. Here we documented the susceptibility of black armyworm, Spodoptera cosmioides (Walker), to three Cry toxins and its life-history traits feeding on dual-toxin Bt cotton and an artificial diet containing sublethal concentrations of Cry1Ac. In concentration–response bioassays, black armyworm larvae showed low susceptibility to Cry toxins, with 853 ng/cm2 as the lowest value estimated for the median lethal concentration (LC50). The decreasing rank of toxicity was Cry1F, Cry2Aa, and Cry1Ac. Foliage of dual-toxin Bt cotton varieties (Cry1Ac + Cry1F and Cry1Ab + Cry2Ae) caused higher larval mortality than Cry1Ac-expressing cotton. Black armyworms showed reduced larval weight when growing on the Cry1Ac-treated diet, yet they reached adulthood and produced offspring. Interestingly, these larvae were grown on the control diet and showed reduced weight gain associated with the toxin exposure of the previous generation, indicating a parental effect of the exposure to Cy1Ac. The reduced larval weight was recovered in later instars, and there was no significant change in the population fitness of the parental armyworms or their offspring. To our knowledge, this is the first study documenting the parental effects of Bt toxins in insects. These results advance our understanding of potential responses of nontarget species when exposed to Bt toxins and contribute to design pest management programs for armyworms and other nontarget lepidopteran species exposed to Bt crops.

Baseline Plant-to-Plant Larval Movement of Spodoptera eridania in Bt and Non-Bt Soybean and Its Possible Impacts on IRM

2020 ◽  
Vol 113 (4) ◽  
pp. 1741-1752
Author(s):  
Thiago L M Fanela ◽  
Edson L L Baldin ◽  
Thomas E Hunt ◽  
Rodrigo D Faria
Keyword(s):  
Larval Mortality ◽  
Pest Species ◽  
Spodoptera Eridania ◽  
Refuge Strategy ◽  
Bt Toxins ◽  
Incomplete Resistance ◽  
Insect Populations ◽  
Transgenic Technologies ◽  
Lepidopteran Pest ◽  
Larval Movement

Abstract The widespread use of transgenic technologies has led to the emergence of insect populations resistant to Bt toxins. Some lepidopteran pest species also appear to naturally have some level of tolerance to certain proteins, such as some species of Spodoptera to Cry1Ac. One of the main strategies to manage resistance is the use of refuge areas, the success of which is in part dependent on larval movement of the target pest. Thus, in order to assess the viability of a refuge strategy addressing Spodoptera eridania Stoll (Lepidoptera: Noctuidae) in Bt soybean, it was evaluated the larval movement across plants in Bt and non-Bt soybean, as well as the larval development and mortality on Bt and non-Bt soybean cultivars. We concluded that apparent S. eridania incomplete resistance resulting from high larval mortality and low adaptability on Bt plants, high larval dispersal, nondirectional larval movement, and random larval spatial dispersion suggest that structured refuge is more suitable than mixed refuge for managing resistance in S. eridania populations.

Global Patterns of Resistance to Bt Crops Highlighting Pink Bollworm in the United States, China, and India

2019 ◽  
Vol 112 (6) ◽  
pp. 2513-2523 ◽  
Author(s):  
Bruce E Tabashnik ◽  
Yves Carrière
Keyword(s):  
United States ◽  
Pest Control ◽  
Crop Residues ◽  
The United States ◽  
Economic Benefits ◽  
Genetically Engineered ◽  
Pink Bollworm ◽  
Bt Cotton ◽  
Pest Species ◽  
Bt Crops

Abstract Crops genetically engineered to produce insecticidal proteins from Bacillus thuringiensis (Bt) have advanced pest control, but their benefits have been reduced by evolution of resistance in pests. The global monitoring data reviewed here reveal 19 cases of practical resistance to Bt crops, which is field-evolved resistance that reduces Bt crop efficacy and has practical consequences for pest control. Each case represents the responses of one pest species in one country to one Bt toxin. The results with pink bollworm (Pectinophora gossypiella) and Bt cotton differ strikingly among the world’s three leading cotton-producing nations. In the southwestern United States, farmers delayed resistance by planting non-Bt cotton refuges from 1996 to 2005, then cooperated in a program that used Bt cotton, mass releases of sterile moths, and other tactics to eradicate this pest from the region. In China, farmers reversed low levels of pink bollworm resistance to Bt cotton by planting second-generation hybrid seeds from crosses between Bt and non-Bt cotton. This approach yields a refuge of 25% non-Bt cotton plants randomly interspersed within fields of Bt cotton. Farmers adopted this tactic voluntarily and unknowingly, not to manage resistance, but apparently because of its perceived short-term agronomic and economic benefits. In India, where non-Bt cotton refuges have been scarce and pink bollworm resistance to pyramided Bt cotton producing Cry1Ac and Cry2Ab toxins is widespread, integrated pest management emphasizing shortening of the cotton season, destruction of crop residues, and other tactics is now essential.

scholarly journals Evaluation of indigenous the nucleopolyhedrovirus (NPV) of Spodoptera litura (Fabricius) (Lepidoptera: Noctuidae) in combination with chlorantraniliprole against Spodoptera species

2021 ◽  
Vol 31 (1) ◽  
Author(s):  
Ghulam Sarwar ◽  
Naeem Arshad Maan ◽  
Muhammad Ahsin Ayub ◽  
Muhammad Rafiq Shahid ◽  
Mubasher Ahmad Malik ◽  
...  
Keyword(s):  
Larval Mortality ◽  
Adult Emergence ◽  
Lethal Concentration ◽  
Pest Species ◽  
Vegetable Crops ◽  
Chemical Insecticide ◽  
Larval Instars ◽  
Novel Method ◽  
High Larval Mortality ◽  
Lepidoptera Noctuidae

Abstract Background The armyworms, Spodoptera exigua (Hübner), and S. litura (Fabricius) (Lepidoptera: Noctuidae) are polyphagous pests of many cash crops. Heavy crop losses have been reported for the fruit and vegetable crops each year owing to the diverse impact on global economies. The present study was aimed to sort out a novel method of pest control using the insect’s own nucleopolyhedrosis virus (NPV) alone and in combination with a new chemistry insecticide chlorantraniliprole. Results In the study, the effect of indigenous isolated nucleopolyhedrovirus (NPV) and the chemical insecticide (chlorantraniliprole) formulations against the 2nd and 4th larval instars of S. litura and S. exigua, collected from the different geographical region of Punjab (Pakistan) province, was evaluated. Three concentrations of the NPV isolate, sub-lethal (1 × 104, 6 × 104 POB ml−1), lethal (3 × 105 POB ml−1), and chlorantraniliprole 0.01 μl l−1, were applied alone and in combination against the 2nd and 4th larval instars of both pest species. The lethal concentration of NPV + chlorantraniliprole exhibited synergistic interaction and caused high larval mortality against both instars, while in all other combinations, additive effect was observed. Moreover, NPV + chlorantraniliprole at lethal concentration exhibited decreased pupation, adult emergence, and egg eclosion. Conclusion The implications of using NPV alone and in combination with an insecticide are discussed briefly in this study.

scholarly journals Need for growing non-Bt cotton refugia to overcome Bt resistance problem in targeted larvae of the cotton bollworms, Helicoverpa armigera and Pectinophora gossypiella

2021 ◽  
Vol 31 (1) ◽  
Author(s):  
Muhammad Rafiq Shahid ◽  
Muhammad Farooq ◽  
Muhammad Shakeel ◽  
Misbah Ashraf ◽  
Zia Ullah Zia ◽  
...  
Keyword(s):  
Helicoverpa Armigera ◽  
Larval Mortality ◽  
Pectinophora Gossypiella ◽  
Bt Cotton ◽  
Insect Larvae ◽  
Plant Parts ◽  
Arthropod Species ◽  
Bt Resistance ◽  
American Bollworm ◽  
Helicoverpa Armígera

Abstract Background The effectiveness of Bacillus thuringiensis (Bt) cotton against target arthropod larvae is decreasing day by day. The comparative effect of Bt expression among Bt cotton varieties and different plant parts was observed against the cotton bollworms: Helicoverpa armigera and Pectinophora gossypiella larvae. Results In the present study, larval mortality of H. armigera was higher than P. gossypiella among selected Bt cultivars. Median lethal concentration (LC50) values were 8.91, 13.4, 14.0, and 36.4 for P. gossypiella, while 5.91, 4.04, 2.37, and 8.26 for H. armigera of FH-142, MNH-886, IR-3701, and FH-Lalazar, respectively. These values depicted that P. gossypiella had more Bt resistance problem than H. armigera larvae. The host range of both targeted insect larvae was different from each other due to the polyphagous feeding nature of the larvae of H. armigera that feed on different host plants, but P. gossypiella attacked only cotton with monophagous feeding habit. It was also notable from results that Bt expression in reproductive parts where the attacked pink bollworm was lower than the American bollworm, so the former had the maximum chance of resistance due to repeated exposure to Bt. Conclusions It was concluded that farmers be advised to follow the practice of growing non-Bt as a refuge crop to reduce the problem of Bt resistance in the target arthropod species.

scholarly journals Dispersal and spatiotemporal distribution of Protapion fulvipes in white clover fields: implications for pest management

2021 ◽  
Author(s):  
Veronica Hederström ◽  
Franklin N. Nyabuga ◽  
Olle Anderbrant ◽  
Glenn P. Svensson ◽  
Maj Rundlöf ◽  
...  
Keyword(s):  
Pest Management ◽  
White Clover ◽  
Insect Pests ◽  
Animal Feed ◽  
Main Tool ◽  
Management Tool ◽  
Pest Species ◽  
Economic Injury Level ◽  
Dispersal Capacity ◽  
Clover Seed

AbstractYield loss caused by insect pests remains a substantial problem in agriculture. Chemical control, with potential negative effects on non-target organisms, is still the main tool for pest management. For pest species with limited dispersal capacity, rotation of the crop in time and space has potential as an alternative management measure. This is particularly important in organic farming, where most agrochemicals are prohibited, but also relevant as a complementary pest management strategy in conventional agriculture. Clover is an important crop used for animal feed and as green manure; however, seed-eating weevils can severely limit the seed yield. We hypothesized that the previous year’s clover seed fields constitute the major sources of weevil pests. Consequently, a greater distance to, and a smaller pest load from, this source should reduce the number of weevils colonizing the new seed fields. To map population dynamics and dispersal range of Protapion fulvipes, an economically important seed weevil specialized on white clover, we conducted field studies over four years in 45 white clover seed fields. We found that P. fulvipes overwinters close to its source field and disperses to new fields in early spring the following year. Pest abundance increased with pest load in the previous year’s seed field, but decreased by 68% per km distance to the previous year’s field. Thus, separation of seed production fields between years by 2–3 km would create a spatiotemporal pest management tool to reduce the pest infestation below the estimated economic injury level.

scholarly journals Impact of Biochar on Douglas-Fir Tussock Moth (Orgyia pseudotsugata Lepidoptera: Erebidae) Larvae Reared on Synthetic Die

Insects ◽  
2021 ◽  
Vol 12 (12) ◽  
pp. 1065
Author(s):  
Stacey Rice-Marshall ◽  
Stephen P. Cook ◽  
John Randall
Keyword(s):  
Weight Gain ◽  
Larval Mortality ◽  
Douglas Fir ◽  
High Concentration ◽  
Larval Weight ◽  
Synthetic Diet ◽  
Tussock Moth ◽  
Orgyia Pseudotsugata ◽  
Compensatory Feeding ◽  
Significant Difference

The use of biochar as a soil amendment in forest ecosystems can be beneficial in the restoration of degraded soils. Forest insects such as the Douglas-fir tussock moth, Orgyia pseudotsugata (McDonnough) (Lepidoptera: Erebidae), may be exposed to biochar when the material is applied. Two experiments were conducted using biochar either (1) applied to the surface of the diet at three rates (0, 5, and 10 mg) or (2) incorporated into synthetic diet at four rates (0, 10, 20, and 40% volume/volume). The objective of both experiments was to determine if biochar on the surface or incorporated into a synthetic diet affected development and survival of O. pseudotsugata larvae. In both experiments, there was a significant decrease in estimated time to larval mortality in all biochar treatments compared to untreated controls. In the surface-applied biochar experiment, there was a significant difference in larval weight gain at day 12 between the control and 10 mg biochar treatments. In the experiment with biochar incorporated into the diet, mean larval weight at day 12 was highest in the low (10%) biochar treatment compared to all other treatments, although weight gain was only significantly different between the low- and high-concentration (40%) biochar treatments. Our results suggest that larvae, feeding on a low amount of biochar in the synthetic diet, may respond by engaging in compensatory feeding behavior. Fewer surviving larvae in the biochar treatment groups may contribute to the lack of significance found in the comparison of weight gain at day 24 in each experiment.

Effects of Ultraviolet-B Radiation on Woundfin Embryos and Larvae with Application to Conservation Propagation

2014 ◽  
Vol 5 (1) ◽  
pp. 87-98 ◽  
Author(s):  
Luke M. Holmquist ◽  
Andrew M. Ray ◽  
Betsy A. Bancroft ◽  
Nick Pinkham ◽  
Molly A. H. Webb
Keyword(s):  
Larval Mortality ◽  
Ultraviolet B ◽  
Mitigation Strategies ◽  
Mitigation Measures ◽  
Parental Effects ◽  
Endangered Fish ◽  
Ultraviolet B Radiation ◽  
Shade Cloth ◽  
Low Levels ◽  
Age At Exposure

Abstract Endangered woundfin Plagopterus argentissimus embryos and larvae were exposed to artificial ultraviolet-B (UV-B) radiation to directly examine the effects on mortality. The experiment was part of a project assisting the Virgin River Resource Management and Recovery Program's efforts to increase hatchery production of this endangered fish. The UV-B radiation used in this experiment was administered in treatments of 0.060, 0.030, and 0.015 mW/cm2 to simulate 100, 50, and 25% of the ambient irradiance levels documented in outdoor tanks and living streams at Bubbling Ponds State Fish Hatchery, in Arizona. Embryos and larvae were exposed for 14.5 h followed by 9.5 h of darkness, in correspondence with the daylight hours at Bubbling Ponds. No embryos survived UV-B treatments; mortality among control (UV-B–free) treatments varied (5–100%) among females, indicating that there may be important parental effects that influence embryo mortality. Larval mortality was also 100% for individuals exposed to any of the three UV-B treatments. In contrast to embryo trials, larval mortality in UV-B–free treatments approached 20% for 2-d-old larvae. These experiments provide evidence that woundfin embryos and larvae are sensitive to even low levels of UV-B when exposed for 14.5 h. Susceptibility of larvae to UV-B also appears to be a function of age at exposure, with older larvae exhibiting significantly lower levels of mortality during the initial days of exposure. Experiments with UV-B mitigation strategies indicated that shade cloth, Aquashade®, and elevated dissolved organic carbon can aid in the attenuation of UV-B, and these strategies may assist hatchery managers in implementing UV-B mitigation measures during periods when woundfin are most susceptible.

scholarly journals Considerations for Insect Learning in Integrated Pest Management

2019 ◽  
Vol 19 (4) ◽  
Author(s):  
Catherine M Little ◽  
Thomas W Chapman ◽  
N Kirk Hillier
Keyword(s):  
Integrated Pest Management ◽  
Pest Management ◽  
Cognitive Abilities ◽  
Insect Pests ◽  
Management Strategies ◽  
Pest Species ◽  
Insect Learning ◽  
Local Ecosystem ◽  
Chemical Pesticides ◽  
Control Insect

AbstractThe past 100 yr have seen dramatic philosophical shifts in our approach to controlling or managing pest species. The introduction of integrated pest management in the 1970s resulted in the incorporation of biological and behavioral approaches to preserve ecosystems and reduce reliance on synthetic chemical pesticides. Increased understanding of the local ecosystem, including its structure and the biology of its species, can improve efficacy of integrated pest management strategies. Pest management strategies incorporating insect learning paradigms to control insect pests or to use insects to control other pests can mediate risk to nontarget insects, including pollinators. Although our understanding of insect learning is in its early stages, efforts to integrate insect learning into pest management strategies have been promising. Due to considerable differences in cognitive abilities among insect species, a case-by-case assessment is needed for each potential application of insect learning within a pest management strategy.

scholarly journals Bioactivity of Common Pesticidal Plants on Fall Armyworm Larvae (Spodoptera frugiperda)

Plants ◽  
2020 ◽  
Vol 9 (1) ◽  
pp. 112 ◽  
Author(s):  
Kelita Phambala ◽  
Yolice Tembo ◽  
Trust Kasambala ◽  
Vernon H. Kabambe ◽  
Philip C. Stevenson ◽  
...  
Keyword(s):  
Pest Management ◽  
Plant Species ◽  
Plant Extracts ◽  
Spodoptera Frugiperda ◽  
Larval Mortality ◽  
Fall Armyworm ◽  
Invasive Pest ◽  
Toxicity Tests ◽  
Contact Toxicity ◽  
Foliar Damage

The fall armyworm (FAW), Spodoptera frugiperda (Lepidoptera: Noctuidae) is a recent invasive pest species that has successfully established across sub-Saharan Africa where it continues to disrupt agriculture, particularly smallholder cereal production. Management of FAW in its native range in the Americas has led to the development of resistance to many commercial pesticides before its arrival in Africa. Pesticide use may therefore be ineffective for FAW control in Africa, so new and more sustainable approaches to pest management are required that can help reduce the impact of this exotic pest. Pesticidal plants provide an effective and established approach to pest management in African smallholder farming and recent research has shown that their use can be cost-beneficial and sustainable. In order to optimize the use of botanical extracts for FAW control, we initially screened ten commonly used plant species. In laboratory trials, contact toxicity and feeding bioassays showed differential effects. Some plant species had little to no effect when compared to untreated controls; thus, only the five most promising plant species were selected for more detailed study. In contact toxicity tests, the highest larval mortality was obtained from Nicotiana tabacum (66%) and Lippia javanica (66%). Similarly, in a feeding bioassay L. javanica (62%) and N. tabacum (60%) exhibited high larval mortality at the highest concentration evaluated (10% w/v). Feeding deterrence was evaluated using glass-fibre discs treated with plant extracts, which showed that Cymbopogon citratus (36%) and Azadirachta indica (20%) were the most potent feeding deterrents among the pesticidal plants evaluated. In a screenhouse experiment where living maize plants infested with fall armyworm larvae were treated with plant extracts, N. tabacum and L. javanica were the most potent species at reducing foliar damage compared to the untreated control whilst the synthetic pesticide chlorpyrifos was the most effective in reducing fall armyworm foliar damage. Further field trial evaluation is recommended, particularly involving smallholder maize fields to assess effectiveness across a range of contexts.

scholarly journals RNA interference as a gene silencing tool to controlTuta absolutain tomato (Solanum lycopersicum)

PeerJ ◽  
2016 ◽  
Vol 4 ◽  
pp. e2673 ◽  
Author(s):  
Roberto A. Camargo ◽  
Guilherme O. Barbosa ◽  
Isabella Presotto Possignolo ◽  
Lazaro E. P. Peres ◽  
Eric Lam ◽  
...  
Keyword(s):  
Rna Interference ◽  
Gene Silencing ◽  
Target Gene ◽  
Target Genes ◽  
Larval Mortality ◽  
Tuta Absoluta ◽  
Specific Gene ◽  
Gene Transcript ◽  
Pest Species ◽  
In Planta

RNA interference (RNAi), a gene-silencing mechanism that involves providing double-stranded RNA molecules that match a specific target gene sequence, is now widely used in functional genetic studies. The potential application of RNAi-mediated control of agricultural insect pests has rapidly become evident. The production of transgenic plants expressing dsRNA molecules that target essential insect genes could provide a means of specific gene silencing in larvae that feed on these plants, resulting in larval phenotypes that range from loss of appetite to death. In this report, we show that the tomato leafminer (Tuta absoluta), a major threat to commercial tomato production, can be targeted by RNAi. We selected two target genes (Vacuolar ATPase-AandArginine kinase) based on the RNAi response reported for these genes in other pest species. In view of the lack of an artificial diet forT. absoluta, we used two approaches to deliver dsRNA into tomato leaflets. The first approach was based on the uptake of dsRNA by leaflets and the second was based on “in planta-induced transient gene silencing” (PITGS), a well-established method for silencing plant genes, used here for the first time to deliverin planta-transcribed dsRNA to target insect genes.Tuta absolutalarvae that fed on leaves containing dsRNA of the target genes showed an ∼60% reduction in target gene transcript accumulation, an increase in larval mortality and less leaf damage. We then generated transgenic ‘Micro-Tom’ tomato plants that expressed hairpin sequences for both genes and observed a reduction in foliar damage byT. absolutain these plants. Our results demonstrate the feasibility of RNAi as an alternative method for controlling this critical tomato pest.

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