Evaluation of Insecticide Thresholds in Late-Planted Bt and Non-Bt Corn for Management of Fall Armyworm (Lepidoptera: Noctuidae)

2020 ◽  
Vol 113 (2) ◽  
pp. 814-823
Author(s):  
Tom R Bilbo ◽  
Francis P F Reay-Jones ◽  
Jeremy K Greene
Keyword(s):  
South Carolina ◽  
Helicoverpa Zea ◽  
Management Strategies ◽  
Fall Armyworm ◽  
Field Trials ◽  
Bt Corn ◽  
Significant Protection ◽  
Corn Hybrids ◽  
Field Corn ◽  
Development Of Resistance

Abstract The fall armyworm, Spodoptera frugiperda (J. E. Smith), is a major pest of corn in North and South America. It is managed primarily with transgenic corn-producing insecticidal proteins of Bacillus thuringiensis (Bt), but the development of resistance threatens their durability and necessitates the use of alternative management strategies. We conducted late-planted field trials during 2016 and 2017 in South Carolina using natural infestations. We evaluated the use of Bt and non-Bt corn hybrids in combination with foliar applications of chlorantraniliprole at varying infestation thresholds to protect field corn from infestation and damage and determine effects on grain yield. All Bt hybrids were more effective at reducing fall armyworm infestation rates and leaf injury than multiple insecticide sprays, and no Bt hybrid reached the lowest infestation threshold (20%) to require supplemental insecticide treatments, despite infestations in non-Bt corn reaching >68% in each year. The only Bt and/or insecticide treatment to significantly reduce ear feeding or the proportion of ears injured (mainly by Helicoverpa zea [Boddie]) was the Bt hybrid pyramid producing Vip3A. However, significant protection of yield was detected only in the Bt hybrids producing Cry1A.105 + Cry2Ab2. All Bt traits tested in this study were effective in reducing infestation and feeding damage from fall armyworm, although this did not always result in significant protection of yield. Our results demonstrate the potential and limitations of using chlorantraniliprole with Bt (when resistance is present) and non-Bt corn to manage this pest.

Susceptibility of Corn Earworm (Lepidoptera: Noctuidae) to Cry1A.105 and Cry2Ab2 in North and South Carolina

2019 ◽  
Vol 112 (4) ◽  
pp. 1845-1857 ◽  
Author(s):  
Tom R Bilbo ◽  
Francis P F Reay-Jones ◽  
Dominic D Reisig ◽  
Jeremy K Greene
Keyword(s):  
United States ◽  
South Carolina ◽  
Helicoverpa Zea ◽  
Natural Populations ◽  
The United States ◽  
Corn Earworm ◽  
Pupal Weight ◽  
Bt Corn ◽  
Development Of Resistance ◽  
Bacterium Bacillus

Abstract The corn earworm, Helicoverpa zea (Boddie), is managed in corn and cotton in the United States primarily using transgenic cultivars that produce insecticidal proteins from the bacterium Bacillus thuringiensis (Bt). However, increasing reports of resistance to one or more Bt proteins threaten the continued efficacy of Bt traits. To better understand the development of resistance of H. zea to Bt corn and cotton in the southeastern United States, we monitored for resistance to Cry1A.105 and Cry2Ab2 among 22 field populations of H. zea collected in non-Bt and Bt corn expressing Cry1A.105 + Cry2Ab2 during 2017 and 2018. Colonies were established in the laboratory and progeny were screened in diet-overlay bioassays to purified Cry1A.105 and Cry2Ab2 proteins. Compared with two susceptible laboratory colonies, all 14 field colonies tested with Cry1A.105 were highly resistant, with resistance ratios (RRs) ranging from 13.5 to >4,000. For Cry2Ab2, 19 colonies were tested and RRs ranged from 0.26 to 33.7. Field populations were significantly more susceptible to Cry2Ab2 than Cry1A.105. We documented variability in F0 and F1 pupal weight and developmental rates of natural populations of H. zea, but observed no significant correlation with susceptibility to either Cry1A.105 or Cry2Ab2. Our results expand on the recent reports of H. zea resistance to Cry1A and Cry2A proteins and will aid in the design and deployment of future pyramided crops in the United States.

Influence of Transgenic Corn Expressing Insecticidal Protein of Bacillus thuringiensis Berliner on Natural Populations of Corn Earworm (Lepidoptera: Noctuidae) and Southwestern Corn Borer (Lepidoptera: Crambidae)

2006 ◽  
Vol 41 (3) ◽  
pp. 221-231 ◽  
Author(s):  
Kerry C. Allen ◽  
Henry N. Pitre
Keyword(s):  
Bacillus Thuringiensis ◽  
Helicoverpa Zea ◽  
Larval Growth ◽  
Natural Populations ◽  
Corn Earworm ◽  
Bt Corn ◽  
Transgenic Corn ◽  
Diatraea Grandiosella ◽  
Corn Hybrids ◽  
Corn Borer

A 2-yr study was conducted to measure the influence of transgenic corn, Zea mays L., expressing the CrylAb endotoxin of Bacillus thuringiensis (Berliner) (Bt) by means of Event MON810 on natural populations of Helicoverpa zea (Boddie) and Diatraea grandiosella (Dyar). The studies were conducted at Leland and Morgan City, MS, in 1999 and at Morgan City in 2000. Although total numbers of H. zea larvae were not significantly different on transgenic corn hybrids compared with their near-isogenic parent lines, fewer large larvae were found on the transgenic hybrids. Differences in H. zea larval growth were noticeable when larvae fed on Bt corn vs non-Bt corn. The delay in larval growth for insects within a single generation, which could possibly result in asynchronous mating between insecticide resistant and susceptible insects, was observed for larvae feeding on plants expressing the Bt toxin. Diatraea grandiosella caused limited damage to the transgenic corn hybrids compared with their near-isogenic parent lines. Yields were not significantly greater for the Bt corn hybrids compared with their near-isogenic parent lines. Yields were not significantly greater for the Bt corn hybrids compared with the near-isogenic, non-Bt corn parents; however, there was a trend toward higher yields for Bt hybrids compared with their near-isogenic non-Bt parents.

scholarly journals CONTROL OF FALL ARMYWORM AND CORN EARWORM WITH SELECTED BT-CORN HYBRIDS, 1999

2000 ◽  
Vol 25 (1) ◽  
Author(s):  
T. J. Riley ◽  
B. A. Castro ◽  
J. Rabb
Keyword(s):  
Fall Armyworm ◽  
Corn Earworm ◽  
Bt Corn ◽  
Corn Hybrids

scholarly journals Impact of Simulated Corn Earworm (Lepidoptera: Noctuidae) Kernel Feeding on Field Corn Yield

2019 ◽  
Vol 112 (5) ◽  
pp. 2193-2198 ◽  
Author(s):  
B M Olivi ◽  
J Gore ◽  
F M Musser ◽  
A L Catchot ◽  
D R Cook
Keyword(s):  
Helicoverpa Zea ◽  
Zea Mays L ◽  
Corn Earworm ◽  
Corn Yield ◽  
Corn Hybrids ◽  
Field Corn ◽  
Lepidoptera Noctuidae ◽  
Economic Pest ◽  
Harvest Method ◽  
Study Manual

Abstract Corn earworm, Helicoverpa zea (Boddie) Lepidoptera: Noctuidae, has not been considered an economic pest of field corn. Historical losses estimates ranged from 1.5 to 2.5%, and a large number of foliar insecticide applications would be needed to minimize infestations. In recent years, Bt, Bacillus thuringiensis (Berliner) field corn, Zea mays (L.) Poales: Poaceae, technologies that exhibit activity against corn earworm have been introduced. However, it is unclear how much damage to corn ears (number of damaged kernels) is required to reduce yield. In this study manual damage methods were utilized to inflict defined levels of kernel damage and to impose damage at levels greater than observed with natural corn earworm infestations. Bt corn hybrids expressing the Agrisure Viptera (Vip 3A) trait were used to minimize injury from natural infestations of corn earworm. Manual kernel damage was imposed at R3 stage to mimic corn earworm feeding while avoiding interference with pollination. These methods were used in experiments where treatments were applied to individual ears and hand-harvested and in experiments where treatments were applied to all primary ears in the plot and machine-harvested. Damage of ≥60 kernels per ear was required to significantly reduce yield regardless of harvest method. Kernel damage from natural corn earworm infestations reported in other studies was much lower than 60 kernels per ear. Timely planting is a key component of all integrated pest management programs. Field corn planted during the recommended planting window for optimum yield is unlikely to experience corn earworm damage great enough to reduce yield.

Evaluation of Corn Hybrids Expressing CrylF (Herculex® I Insect Protection) Against Fall Armyworm (Lepidoptera: Noctuidae) in the Southern United States

2008 ◽  
Vol 43 (1) ◽  
pp. 41-51 ◽  
Author(s):  
Melissa Willrich Siebert ◽  
Kelly V. Tindall ◽  
B. Rogers Leonard ◽  
John W. Van Duyn ◽  
Jonathan M. Babcock
Keyword(s):  
Spodoptera Frugiperda ◽  
Zea Mays L ◽  
Larval Mortality ◽  
Fall Armyworm ◽  
Laboratory Studies ◽  
Insecticidal Crystal Protein ◽  
Corn Hybrids ◽  
Field Corn ◽  
Field Plots ◽  
Lepidoptera Noctuidae

Efficacy of two insect-resistant corn hybrids expressing the Cry1 F insecticidal crystal protein of Bacillus thuringiensis var. aizawai Berliner (transformation event TC1507) was evaluated against fall armyworm, Spodoptera frugiperda (J.E. Smith), in three southern U.S. locations. Larval susceptibility was evaluated on CrylF and nonBt field corn, Zea mays L., plants (V3–V12 and R1–R2 stages) in field plots and laboratory studies. Leaf-feeding injury was significantly less and plant height was significantly greater for hybrids containing Cry1 F as compared with nonBt corn hybrids when exposed to natural or artificial fall armyworm infestations. In addition, larval mortality was significantly greater on CrylF corn hybrids compared with that on nonBt hybrids. These results demonstrate that corn hybrids containing CrylF represent an effective plant incorporated insecticidal protein management option for fall armyworm. In environments where fall armyworm may exceed damage thresholds and have to be carefully managed with foliar sprays, utilization of CrylF corn hybrids will allow growers flexibility in planting and an efficient means for managing infestations.

scholarly journals Decline in Sublethal Effects of Bt Corn on Corn Earworm (Lepidoptera: Noctuidae) Linked to Increasing Levels of Resistance

2020 ◽  
Vol 113 (5) ◽  
pp. 2241-2249 ◽  
Author(s):  
Francis P F Reay-Jones ◽  
Thomas R Bilbo ◽  
Dominic D Reisig
Keyword(s):  
South Carolina ◽  
Sublethal Effects ◽  
Sublethal Effect ◽  
Fold Increase ◽  
Field Trials ◽  
Corn Earworm ◽  
Genetically Engineered ◽  
Pupal Weight ◽  
Bt Corn ◽  
North And South

Abstract As part of an ongoing longitudinal study in North and South Carolina, this study reports the recovery of Helicoverpa zea (Boddie) pupae in field trials with genetically engineered corn, Zea mays L., hybrids that produce insecticidal toxins from Bacillus thuringiensis (Bt) in 2017–2019. In total, 10,400 corn ears were collected, which led to 3,927 H. zea pupae (2,215 in South Carolina and 1,712 in North Carolina). Late-planted corn led to a 3.39-fold increase in recovery of pupae compared to early-planted corn. Bt corn expressing Cry1F + Cry1Ab and Cry1A.105 + Cry2Ab2 had 1.67-fold and 2.51-fold fewer pupae than non-Bt near-isolines, respectively. Only six pupae were recovered from the hybrid expressing Cry1F + Cry1Ab + Vip3Aa20. Averaged across trials, Bt corn expressing either Cry1A.105 + Cry2Ab2 or Cry1F + Cry1Ab significantly reduced pupal weight compared to non-Bt near-isolines in North and South Carolina. Combining our data with a previous study at the same locations (Bilbo et al. 2018), reduction in pupal weight between Bt and non-Bt near-isolines significantly declined from 2014 to 2019 for Cry1Ab + Cry1F in North and South Carolina. This decline in levels of a sublethal effect of Bt corn expressing Cry1Ab + Cry1F on H. zea at both locations is likely correlated with resistance development.

scholarly journals EVALUATION OF SELECTED BT CORN HYBRIDS AGAINST CORN EARWORM AND FALL ARMYWORM, 1998

1999 ◽  
Vol 24 (1) ◽  
Author(s):  
T. J. Riley ◽  
B. A. Castro ◽  
C. Cálix ◽  
J. Rabb
Keyword(s):  
Fall Armyworm ◽  
Corn Earworm ◽  
Bt Corn ◽  
Corn Hybrids

scholarly journals Efficiency of biological control for fall armyworm resistant to the protein Cry1F

2020 ◽  
Author(s):  
C. S. F. Souza ◽  
L. C. P. Silveira ◽  
B. H. S. Souza ◽  
P. T. Nascimento ◽  
N. C. R. Damasceno ◽  
...  
Keyword(s):  
Biological Control ◽  
Integrated Management ◽  
Genetically Modified ◽  
Management Strategies ◽  
Search Time ◽  
Pest Resistance ◽  
Fall Armyworm ◽  
Bt Corn ◽  
Predatory Behaviour ◽  
Predatory Capacity

Abstract Understanding the ecological and toxicological relationship between genetically modified cultivars (GM) and biological control agents is of great importance for discussions related to the compatability of GM cultivars and integrated management strategies for pest resistance. The present study evaluated the search behavior and predatory capacity of Orius insidiosus (Say) (Hemiptera: Anthocoridae) and Doru luteipes (Scudder) (Dermaptera: Forficulidae) on eggs and caterpillars of Spodoptera frugiperda (J. E. Smith) (Lepidoptera: Noctuidae) resistant or not to the protein Cry1F expressed in Bt corn. To determine the search time, a stopwatch was run until the capture of the first prey, predation capacity was evaluated by counting the prey remaining after 24 hours of infestation. The injuries of S. frugiperda in genetically modified and conventional corn in the presence and absence of predators was also evaluated. The predators were not able to distinguish between resistant and susceptible prey (eggs or caterpillars), given the predatory behaviour observed. There was no difference in searching time or predatory capacity between the predators for eggs and caterpillars of either resistant or susceptible S. frugiperda. In the presence of predators, the injury scores for resistant S. frugiperda on the Bt corn plants were lower. It was concluded that O. insidiosus and D. luteipes did not notice the presence of the protein Cry1F in the prey S. frugiperda, which may facilitate the combined use of GM corn and biological control in integrated management programs and for management of pest resistance.

Evaluation of Bt Transgenic Sweet Corn Hybrids for Resistance to Corn Earworm and Fall Armyworm (Lepidoptera: Noctuidae) using a Meridic Diet Bioassay2

1999 ◽  
Vol 34 (4) ◽  
pp. 415-425 ◽  
Author(s):  
B. R. Wiseman ◽  
R. E. Lynch ◽  
D. Plaisted ◽  
D. Warnick
Keyword(s):  
Spodoptera Frugiperda ◽  
Helicoverpa Zea ◽  
Sweet Corn ◽  
Fall Armyworm ◽  
Corn Earworm ◽  
Laboratory Bioassay ◽  
Corn Hybrids ◽  
Pinto Bean ◽  
Highly Correlated ◽  
Lepidoptera Noctuidae

A laboratory bioassay was used to evaluate Bt transgenic sweet corn hybrids for resistance against the corn earworm, Helicoverpa zea (Boddie), and the fall armyworm, Spodoptera frugiperda (J. E. Smith). Whorl leaves, silks, and kernels, either fresh or oven-dried and ground with a mill, were incorporated into a dilute pinto bean diet and bioassayed against neonate, 3-, or 6-day-old larvae. Regardless of age of the larvae, results with the diet bioassay using fresh silks, oven-dried silks or fresh kernels were highly correlated with those for the fresh silk bioassay. Differences in susceptibility between insect species to the CrylA(b) toxin produced in the transgenic plants were also readily discernable using the diet bioassay. Based on results of the bioassays, Novartis sweet corn hybrids containing a crylA(b) gene gene for δ-endotoxin production were very highly resistant to leaf, silk and kernel feeding by the corn earworm and highly resistant to leaf and silk feeding by the fall armyworm.

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