iArcsine square root % transformed data used for analysis, non-transformed means presented in table. Sweet corn planted in late April and early May and produced with insecticide applications for corn earworm can sometimes escape damage. 1 Foster, R. 2017. Corn also serves as the primary nursery for generation turnover of CEW populations which eventually shift to soybean later in the growing season. Timing is crucial, so the observant gardener won’t try to spray the moths or eggs, only the leaves the larvae will eat. 7 Venugopal, P. and Dively, G. 2017 Climate change, transgenic corn adoption and field-evolved resistance in corn earworm. Means within columns followed by a common letter are not significantly different (P ≤ 0.05, FPLSD). Corn earworm larvae generally infest the ear through the silk and in years with heavy insect pressure, there can be multiple penetration sites. On 29 Aug at the R5 growth stage, the number of corn earworm damaged kernels was determined on 10 ears per plot. Search for other works by this author on: © The Author(s) 2020. Bt corn should not be used as a stand-alone tactic to manage corn earworm nor is it marketed that way by seed companies. 2014, Reay-Jones and Reisig 2014, B ibb et al. Plot size was four rows (40 in centers) by 40 ft. Hybrids/Bt technologies were replicated four times in an RCB design. (Photo credit: Dominic Reisig, Ph.D.) By the year 2015, 81% of the field corn and 84% of the cotton crop grown in the U. S. contained Bt traits.4 This widespread use of Bt crops has put a strong selection pressure on populations of CEW to become resistant to the Bt proteins, and levels of damage from CEW have increased in Bt field corn and cotton over the past few years.6 The effectiveness of using Bt sweet corn hybrids to manage CEW also has declined, and sweet corn growers in some areas have stopped using Bt hybrids or are increasing their use of insecticides to manage the pest.4,7. There are two general fights to the Midwest every summer, but the first flight is not of economic concern. While this gene will provide some control of corn earworms, many of the varieties that contain a single Bt gene do not provide sufficient control and also require a regular insecticide spray program used with it. The number of ears with feeding damage was also recorded. Plots planted to Dekalb DKC6697 (VT Double Pro) or Pioneer P1319VYHR (Optimum Leptra) had fewer large larvae compared to plots planted to either of the non-Bt hybrids (Dekalb DKC 6694 or Pioneer P1319R). Oxford University Press is a department of the University of Oxford. Corn earworm. Decreased susceptibility of corn earworm to Cry toxins in Bt sweet corn was confirmed a couple of years ago and these are the same Cry toxins expressed in field corn. Transgenic corn, Zea mays L., hybrids expressing insecticidal proteins from Bacillus thuringiensis (Bt) and non-Bt near isolines were sampled for injury from Helicoverpa zea (Boddie) in North and South Carolina from 2012 to 2017. Entfact-318. Corn earworm (Photo 1) is common in Iowa corn. Journal of Invertebrate Pathology 163:11-20. Published by Oxford University Press on behalf of Entomological Society of America. Occurrence and ear damage of Helicoverpa zea on transgenic Bacillus thuringiensis maize in the field in Texas, US and its susceptibility to Vip3A protein. 2001). Donald R Cook, Jeffrey Gore, Whitney Crow, Performance of Selected Bt Corn Hybrids/Technologies Against Corn Earworm, 2016, Arthropod Management Tests, Volume 45, Issue 1, 2020, tsaa095, https://doi.org/10.1093/amt/tsaa095. Delta Mississippi Research and Extension Center, Mississippi State University. During periods of warmer temperatures, insecticides may need to be applied more frequently because the silks grow faster (up to 1 inch per day), and newly emerged silks are not protected.1. dOptimum Leptra expresses the Cry1F, Cry1Ab, and Vip3A proteins. With the acreages involved, the development of Bt-resistant strains of CEW is influenced more by the use of Bt field corn and cotton than by the use of Bt sweet corn. Feeding on unfertilized and/or aborted kernels at the ear tip was excluded. aVT Double Pro expresses the Cry1A.105 and Cry2Ab2 proteins. However, this will not completely prevent all damage from the pest, and spraying with pesticides is sometimes necessary. Corn earworm larvae were categorized as small (1st and 2nd instar), medium (3rd and 4th instar), or large (5th and 6th instar). Z., Dimase, M., and Huang, F. 2019. In 2019, reports of higher numbers of corn earworms observed feeding on Bt field corn, are raising concerns for potential decreased susceptibility to Bt … Corn with Vip3a will not produce many moths at all, and cotton with Vip3a will not have much damage. CAUTION! Now EPA wants to know as soon as Bt corn or cotton fields experience certain levels of unexpected injury from insects such as corn earworm/bollworm, fall armyworm or … 2016). Using Bt corn could significantly reduce the CEW populations and could be an … The Bt genes that have been used in commercial sweet corn hybrids to date include Cry1Ab, … Decreased susceptibility of corn earworm to Cry toxins in Bt sweet corn was confirmed a couple of years ago and these are the same Cry toxins expressed in field corn. Some hybrids contain a combination of the Cry1A.105 and Cry2Ab2 genes, and some contain a combination of the Cry1Ab and Vip3A genes.4 Initially, Bt hybrids of sweet corn were very resistant to CEW damage, and the need for insecticide applications was reduced for plantings of these hybrids in many situations.5. Hybrids containing both the Cry1A.105 and Cry2Ab2 genes were included in the study starting in 2010, and these hybrids showed 20.2% ear damage in 2010 and 59.5% damage in 2016. University of Kentucky Cooperative Extension. In corn, corn earworm (same insect as cotton bollworm) can occasionally cause significant direct yield from feeding, but most often causing losses by providing an entry point for mycotoxins. Field-evolve resistance of Helicoverpa zea (Boddie) to transgenic maize expressing pyramided Cry1A.105/Cry2Ab2 proteins in northeast Louisiana, the United States. Damaged kernels are presented as number of damaged kernels per ear. These hybrids should still be effective for controlling European corn borer, and many of the Bt hybrids also have some form of herbicide tolerance, which will still be effective. Helicoverpa zea is a prevalent pest of corn targeted by Bt traits in the southeastern United States (Cartwright 1939, Reay-Jones and Reisig 2014, Reay-Jones et al. Thus, growers that plant non-Bt corn can help delay bollworm resistance to Bt without sacrificing yield. It is a migratory pest, migrating from the southern and southeastern U.S. every summer. For additional agronomic information, please contact your local seed representative. Decreased susceptibility of corn earworm to Cry toxins in Bt sweet corn was confirmed a couple of years ago and these are the same Cry toxins expressed in field corn. http://pmep.cce.cornell.edu/profiles/extoxnet/24d-captan/btext.html. Other studies have shown similar results with Bt field and sweet corn.6,8 A study of Bt field corn in Texas found populations of CEW that showed resistance to the Vip3A protein, indicating that this trait may also become less effective in sweet corn in the near future.6. The variety known as Bt sweet corn has been genetically engineered to kill certain caterpillars, including corn ear rooms. 4: 170210. 9067_S1 Published 10-13-2019. Corn earworm larva feeding on kernels and causing ear damage. ALWAYS READ AND FOLLOW IRM, WHERE APPLICABLE, GRAIN MARKETING AND ALL OTHER STEWARDSHIP PRACTICES AND PESTICIDE LABEL DIRECTIONS. 8 Kaur, G., Guo, J. G., Brown, S., Head, G. P., Price, P. A., Paula Moraes, S., Ni, X. The recommendations in this article are based upon information obtained from the cited sources and should be used as a quick reference for information about sweet corn pests. 3 Pesticide Information Profile: Bacillus thuringiensis. Decreased susceptibility of corn earworm to Cry toxins in Bt sweet corn was confirmed a couple of years ago and these are the same Cry toxins expressed in field corn. Some hybrids contain just the Cry1Ab gene. The Heliothus zea has the distinction of being the most destructive corn pest in the United States. All other trademarks are property of their respective owners. Hybrids that contained both the Cry1Ab and Vip3A genes did not show any damage from CEW feeding. One of the most popular methods of controlling cotton bollworm/corn earworm is the use of transgenic Bt … For Bt sweet corn Growers should evaluate data from multiple locations and years whenever possible and should consider the impacts of these conditions on the grower’s fields. It furthers the University's objective of excellence in research, scholarship, and education by publishing worldwide, This PDF is available to Subscribers Only. 6 Yang, F., Gonzalez, J. C. S., Williams, J., Cook, D. C., Gilreath, R. T., and Kerns, D. L. 2019. The hybrids containing only the Cry1Ab gene showed the greatest level of change with 6.3% ear damage in 1996 and 85.1% ear damage in 2016. A. PLoS ONE 11(12): e0169115. The content of this article should not be substituted for the professional opinion of a producer, grower, agronomist, pathologist and similar professional dealing with this specific crop. written by: Darsy Smith & Veronica Yurchak Dr. Galen Dively, a Professor Emeritus in the Department of Entomology at the University of Maryland, has become a leading figure in the effort to monitor and mitigate resistance development to genetically modified Bt corn, primarily addressing the very destructive corn earworm. Similar to Bt field corn, Bt sweet corn has been genetically engineered with a protein that kills certain caterpillars. dOptimum Leptra express the Cry1F, Cry1Ab, and Vip3A proteins. A total of 7,260 ears were sampled, with an average kernel injury from H. zea feeding of 1.22 ± 0.02 (SEM) cm2. Efficacy of Bt hybrids/technologies against corn earworm was determined by examining 20 ears per plot on 11 Jul at the R3 growth stage for the presence of larvae and damage. virtually 100% controlled by Bt sweet corn. With most sweet corn hybrids, insecticide applications need to begin when 30% to 50% of plants are showing silks and CEW moths are present at levels above the action threshold (Table 1).1,9 Recommended threshold levels vary somewhat among regional production guides 1,9, and thresholds should be adjusted based on temperature and the presence of silking field corn. Purdue University Extension Entomology, Vegetable Insects, E-31-W. Corn earworm management in sweet corn. © 2019 Bayer Group. It is very selective, safe to beneficial insects, and has been approved for commercial production. Damage was described as feeding on fertilized and developed kernels. In 2019, reports of higher numbers of corn earworms observed feeding on Bt field corn, are raising concerns for potential decreased susceptibility to Bt … Pheromone trap for corn earworm. developed Bt sweet corn varieties against the corn earworm, H. zea, and to compare harvest yields for fresh market and processing uses. CEW is also known as the tomato fruitworm and the cotton bollworm, and it is a pest on corn, tomato, cotton, beans, alfalfa, and tobacco.1,2, Bt hybrids of sweet corn contain one or more genes from the naturally occurring soil bacterium Bacillus thuringiensis (Bt) that result in the production of proteins that disrupt the digestive systems of certain groups of insects.3 Different strains of the bacterium produce different insecticidal proteins, and the genes that code for these proteins have been used to develop insect-resistant crops, including corn and cotton.4, Sweet corn hybrids with Bt traits first became commercially available in the late 1990s to help manage insect pests such as corn earworm and European corn borer. Bacillus thuringiensis. All rights reserved. Figure 1. A spray pressure of 30 psi or more is recommended to get adequate coverage.2 Once a larva enters the ear it is protected by the husk and very difficult to kill with insecticide applications. This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (, Efficacy of Foliar Insecticides Against Green Stink Bug and Green Cloverworm in Soybean, 2020, Laboratory Bioassays of Biological/Organic Insecticides to Control Corn Earworm on Hemp in Virginia, 2019, Efficacy Foliar Applied Insecticides on Tobacco Budworm in Flue-Cured Tobacco, 2020, Insecticide Efficacy Against Corn Earworm in Sweet Corn, 2019, About the Entomological Society of America, http://creativecommons.org/licenses/by-nc/4.0/, Receive exclusive offers and updates from Oxford Academic, Copyright © 2020 Entomological Society of America. 3 The corn earworm (Helicoverpa zea Boddie) is a common insect in corn. Bayer, Bayer Cross Design, and Seminis® are registered trademarks of Bayer Group. There were no differences among hybrids/Bt technologies observed for yield.1. Figure 2. eArcsine square root % transformed data used for analysis, non-transformed means presented in table. While IRM for Bt corn has proved effective in delaying O. Lower moth count action thresholds and more frequent insecticide applications may be needed to obtain acceptable levels of control on Bt hybrids than were needed in the past. This research was supported in part by industry gifts of pesticides, seed, and/or research funding. 5 Dively, G., Venugopal, P., Bean, D., Whalen, J., Holmstrom, K., Kuhar, T., Doughty, B., Patton, T., Cissel, W., and Hutchison, W. 2018. Again feeding on unfertilized and/or aborted kernels at the ear tip was excluded. A study on the effectiveness of using Bt sweet corn for managing CEW was conducted between 1996 and 2016 in Maryland.4 The non-Bt hybrids showed average ear damage levels of 82.4%, and that level was constant over the 20 years of the study. 9 Egel, D., Foster, R., Maynard, E., Weller, S., Babadoost, M., Nair, A., Rivard, C., Kennelly, M., Hausbedk, M., Szendra, Z., Hutchinson, B., Eaton, T., Welty, C., and Miller, S. 2019.