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.

Stadia, Larval-Pupal Weight, and Width of Head Capsules of Corn Earworm (Lepidoptera: Noctuidae) After Feeding on Varying Resistance Levels of Maize Silks

1991 ◽  
Vol 26 (3) ◽  
pp. 303-309
Author(s):  
B. R. Wiseman ◽  
D. J. Isenhour ◽  
V. R. Bhagwat
Keyword(s):  
Helicoverpa Zea ◽  
Zea Mays L ◽  
Head Capsule ◽  
Developmental Time ◽  
Corn Earworm ◽  
Pupal Weight ◽  
Susceptible Genotype ◽  
Resistant Material ◽  
Maize Silks ◽  
Lepidoptera Noctuidae

Weight of larvae, developmental time to pupation, weight of pupae, length of stadia, and width of head capsule were determined for larvae of the corn earworm, Helicoverpa zea (Boddie), that were fed on meridic diets with silks of ‘Stowell's Evergreen’, a susceptible genotype, or low, intermediate, and high levels of ‘Zapalote Chico’, a corn, Zea mays L., cultivar with antibiotic resistance. As the level of resistance increased, the weight of larvae at 9 days and weight of pupae significantly decreased, and developmental time to pupation significantly increased. Also, as the concentration of resistant material increased in the diet, stadial length also significantly increased. The intermediate and high levels of resistance also resulted in a significant reduction in the width of the head capsule of larvae. Thus, two new characteristics of resistance in maize silks to the corn earworm were identified: increased stadia and decreased width of head capsule.

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.

scholarly journals Pest Status and Management of Corn Earworm (Lepidoptera: Noctuidae) in Field Corn in the United States

2019 ◽  
Vol 10 (1) ◽  
Author(s):  
Francis P F Reay-Jones
Keyword(s):  
United States ◽  
Selection Pressure ◽  
The United States ◽  
Corn Earworm ◽  
Bt Corn ◽  
Pest Status ◽  
Field Corn ◽  
Type Of Injury ◽  
The Impact ◽  
Economic Pest

Abstract The corn earworm, Helicoverpa zea (Boddie), is a common lepidopteran pest of corn (Zea mays L.) in the United States. This article provides an overview of the life history, ecology, plant injury, and management of H. zea in corn. Leaf injury by H. zea feeding can occur in vegetative stage corn, though this type of injury is rare. The most common type of injury is caused by larval feeding in ears. Because kernel injury is typically limited to the tip of the ear, H. zea is generally not considered an economic pest. The use of transgenic corn hybrids expressing insecticidal Cry proteins from Bacillus thuringiensis (Bt) Berliner can reduce injury from H. zea, though complete control is not achieved with most Bt traits. Resistance has been reported to several Bt toxins. Because H. zea is a major economic pest in cotton (Gossypium hirsutum L.) and because H. zea moths that developed on corn can migrate to cotton, selection pressure on H. zea in Bt corn has major implications for the pest status and injury to Bt cotton. Although the impact of H. zea on yield of field corn is generally negligible, the selection pressure exerted by Bt corn has led to management issues in cotton.

Field Evaluation of Transgenic Corn Containing a Bacillus thuringiensis Berliner Insecticidal Protein Gene Against Helicoverpa zea (Lepidoptera: Noctuidae)

1996 ◽  
Vol 31 (3) ◽  
pp. 340-346 ◽  
Author(s):  
Steven R. Sims ◽  
Jay C. Pershing ◽  
Barbara J. Reich
Keyword(s):  
Bacillus Thuringiensis ◽  
Helicoverpa Zea ◽  
Negative Relationship ◽  
Field Evaluation ◽  
Corn Earworm ◽  
Insecticidal Protein ◽  
Transgenic Corn ◽  
First Instar ◽  
Transgenic Lines ◽  
Lepidoptera Noctuidae

Twelve independently transformed lines of transgenic corn (Zea mays L.) expressing the CryIA(b) insecticidal protein from Bacillus thuringiensis var. kurstaki were field tested to evaluate their resistance to the corn earworm, Helicoverpa zea (Boddie). Silks of the primary (=top) ears of transgenic [CryIA(b) positive] and isoline control plants [no CryIA(b) protein] were artificially infested with first-instar H. zea larvae and the length of ear penetration was measured after 19 d. Eight of the 12 lines had significantly less ear damage than their respective isoline controls; 3 transgenic lines reduced H. zea feeding damage by > 75% and stunted surviving H. zea larvae. Concentration of the CryIA(b) protein (μg/g fresh weight) in silks of the transgenic lines, determined using ELISA, ranged from 0.0 to 1.28 μg/g. Within transgenic lines, there was a weak (P < 0.06) negative relationship between the concentration of CryIA(b) protein in fresh silks and the length of H. zea ear penetration.

Influence of Panicle Maturity on Infestation of Grain Sorghum by Corn Earworm and Sorghum Webworm (Lepidoptera: Noctuidae) in Georgia

1991 ◽  
Vol 26 (4) ◽  
pp. 419-424
Author(s):  
J. R. Chamberlin ◽  
J. N. All
Keyword(s):  
Helicoverpa Zea ◽  
Paired Comparison ◽  
Larval Density ◽  
Field Tests ◽  
Grain Sorghum ◽  
Corn Earworm ◽  
Egg Parasitism ◽  
Low Levels ◽  
Sorghum Webworm ◽  
Lepidoptera Noctuidae

The influence of panicle maturity on oviposition by the corn earworm, Helicoverpa zea (Boddie), and sorghum webworm, Celama sorghiella (Riley), was investigated on grain sorghum in Georgia during 1986 and 1987. Stage of panicle development, density of corn earworm and sorghum webworm, and egg parasitism by Trichogramma spp. were recorded at 2–3 day intervals in three field tests. Sorghum webworm and corn earworm began oviposition as panicles emerged from the boot. Oviposition peaked 4–8 days later, near the time panicles began anthesis, but then declined quite rapidly. Oviposition by sorghum webworm ceased approximately 10–12 days after panicle emergence began. Corn earworm oviposition continued at low levels until sampling was terminated 14 - 17 days after panicles began emgergence. Rainfall appeared to mediate effects of panicle maturity on oviposition. Corresponding peaks in larval density were not observed for corn earworm or sorghum webworm, possibly because of heavy parasitism by Trichogramma spp. A paired comparison procedure was used to determine preference of small, medium, and large corn earworm larvae for panicles of different maturity. Early instars preferred newly flowered panicles and concentrated feeding on pollen filled anthers. Late instars preferred panicles in the soft-hard dough stages, while intermediate instars exhibited no significant preference. These data suggest that corn earworm oviposition is concentrated at anthesis because pollen enhances larval development and survival.

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