Phytotoxicity and Pollination Disorders in Sweet Corn Due to Direct-silk Applications of Materials Used for Alternative Corn Earworm Control

Corn earworm [CEW (Helicoverpa zea)] is one of the most important pests of sweet corn (Zea mays) in New England. Conventional management of this pest is achieved through repeated applications of chemical insecticides through the silking period. Organic growers, however, have few alternatives to prevent CEW infestation. Technology first developed in the 1930s and 1940s, using applications of mineral oil directly into the silk channel with an eyedropper, has been further researched in recent years using vegetable oils with and without pesticides, but pollination problems associated with these treatments have been observed. Several materials were evaluated for efficacy in controlling CEW populations and for phytotoxicity to the developing ear. Materials evaluated were corn oil, soy oil, carrageenan, corn oil mixed with Bacillus thuringiensis ssp. kurstaki (Bt), soy oil mixed with Bt, and carrageenan mixed with Bt. All treatments were compared with an untreated control. Treatments provided a range of 33% to 50% control of CEW infestation. The oil and Bt combinations provided some reduction in infestation compared with the untreated controls (33% vs. 100% infestation), but this level of control was inadequate for all wholesale markets and most direct markets. Additionally, oil-based treatments also caused significant injury to developing ears by reducing pollination quality, impacting the development of the kernels at the ear tip. This condition referred to as “cone-tip” is of concern since it may decrease marketability. The percent unmarketable ears due to cone-tips ranged from 0% to 13% for the untreated and carrageenan-based treatments. From 12% to 42% of ears were unmarketable due to the soy oil treatments. Corn oil treatments caused 10% to 50% cone-tips.

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Field Bioassay of Pheromone Lures and Trap Designs for Monitoring Adult Corn Earworm (Lepidoptera: Noctuidae) in Sweet Corn in Southern New England

Review & Expositor ◽

10.1177/003463732001700319 ◽

1920 ◽

Vol 17 (3) ◽

pp. 1833-1836

Author(s):

Norman L. Gauthier ◽

Patrick A. Logan ◽

Lisa A. Tewksbury ◽

Craig F. Hollingsworth ◽

Donald C. Weber ◽

...

Keyword(s):

New England ◽

Rhode Island ◽

Helicoverpa Zea ◽

Sweet Corn ◽

Corn Earworm ◽

Reference Standards ◽

Fresh Market ◽

Field Bioassay ◽

Southern New England ◽

Lepidoptera Noctuidae

Four commercial pheromones attractive to Helicoverpa zea (Boddie) were used as baits in four insect traps to attract moths in fresh market sweet corn. Moth catches were monitored for 10 wk in nine sites in Connecticut, Massachusetts, and Rhode Island. Zealure attracted twice as many moths as Scentry's corn earworm lure and nine times as many as Pherocon's corn earworm lure. Consep Membrane's Biolure attracted few moths. Hartstack traps caught three times more moths than Heliothis net traps and 15 times more than Multi-pher or International Pheromone Systems traps. Results suggest the need for reference standards in management programs that use pheromones to monitor corn earworm populations.

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Direct Silk Applications of Corn Oil and Bacillus thuringiensis as a Barrier to Corn Earworm Larvae in Sweet Corn

HortTechnology ◽

10.21273/horttech.13.3.0509 ◽

2003 ◽

Vol 13 (3) ◽

pp. 509-514 ◽

Cited By ~ 7

Author(s):

Rosalind Cook ◽

Anne Carter ◽

Pam Westgate ◽

Ruth Hazzard

Keyword(s):

Bacillus Thuringiensis ◽

Helicoverpa Zea ◽

Sweet Corn ◽

Corn Oil ◽

Field Studies ◽

Corn Earworm ◽

Untreated Plot ◽

Promising Alternative ◽

First Instar ◽

Almost All

Field studies were conducted in 2000 and 2001 to rate the efficacy and longevity of four pesticide treatments against corn earworm (Helicoverpa zea) larvae (CEW) in sweet corn (Zea mays). The four treatments used were 1) corn oil, 2) Bacillus thuringiensis ssp. kurstaki (Bt), 3) oil + Bt, and 4) an untreated plot. All treatments were applied on silk day 5. Silk day 1 was the first day that more than 50% of the ears had 2.5 cm (1 inch) or more silks emerging from the husk using a hand-held pump applicator. Two first-instar CEW larvae were placed directly into silk channel of selected ears on 6 different days (days 3, 6, 9, 12, 15, and 18 after first silk). The same six ears were then harvested 4 days later. Untreated ears had more live CEW and higher levels of feeding damage than the other three treatments ears for all harvest days in both years. The number of CEW found per ear was lower when Bt was included in the treatment. The use of corn oil gave the lowest damage ratings on almost all harvest days in both years. Treatments which contained oil had the highest number of marketable ears in both years, but also the highest percentage of underdeveloped kernels at the tip of the ear (6% to 9%). The oil and Bt treatments appeared to control CEW for at least 17 days, from silking through maturity. This treatment regime appears to be a promising alternative for growers to conventional pest management methods.

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Optimum Timing of an Application of Corn Oil and Bacillus thuringiensis to Control Lepidopteran Pests in Sweet Corn

HortTechnology ◽

10.21273/horttech.14.3.0307 ◽

2004 ◽

Vol 14 (3) ◽

pp. 307-314 ◽

Cited By ~ 4

Author(s):

Rosalind Cook ◽

Anne Carter ◽

Pamela Westgate ◽

Ruth Hazzard

Keyword(s):

Bacillus Thuringiensis ◽

Helicoverpa Zea ◽

European Corn Borer ◽

Sweet Corn ◽

Corn Oil ◽

Corn Earworm ◽

Larval Feeding ◽

Corn Borer ◽

Late Planting ◽

All Treatment

Corn oil and Bacillus thuringiensis ssp. kurstaki (Bt) applied directly into the silk channel of a corn ear has been shown to be an effective pesticide against corn earworm, Helicoverpa zea (CEW), and european corn borer, Ostrinia nubilalis (ECB). Field studies were conducted in 2000 and 2001 to determine the influence of application timing on ear quality at harvest. Two blocks of corn were planted during each year to observe treatment effects under varying populations of the two insect species. The treatment consisted of 0.5 mL (0.017 floz) of food grade corn oil containing a suspension of Bt at 0.08 g (0.003 oz) a.i. per ear applied directly into the silk channel at the husk opening. One treatment application was made on each silk day 3 through 11 from first silk; silk day 1 was the first day that 50% or more of ears had 2.5 cm (1 inch) of silk protruding from the husk. One treatment did not receive the oil + Bt suspension. All ears were harvested at milk stage, on silk day 25. The number of CEW larvae in treated ears increased with later application days in 2000, but not in 2001. Damage from larval feeding was mainly found near the tip of the ear, and damage ratings were lower compared to untreated ears for all treatment days for both plantings in 2000, and through application day 8 in the late planting of 2001. ECB larvae were reduced for all treatment days in both plantings in 2000 and the late planting of 2001. The percentage of ears rated as marketable (i.e., free of feeding damage) ranged from 71% to 100% in treated plots compared to 30% to 77% in the untreated plots. There was a linear decrease in marketability with later application days in two of the four plantings. The greatest decrease in marketability was after application day 7. Because the oil application affects kernel development at the tip, the length of ear with under-developed kernels, or cone tip, was measured. The number of ears with cone tip decreased linearly with the later application days in all plantings. There was 10% conetip or less after day 7 in 2000 and day 6 in 2001. The best combination of effective insect control resulting in the highest rates of marketable ears with the least degree of cone tip was achieved in this experiment by application of oil + Bt suspension on day 7. Year to year variation in the environment would suggest a range from day 6 to 8.

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EVALUATION OF THURICIDE/CORN OIL APPLICATIONS FOR CORN EARWORM MANAGEMENT ON SWEET CORN, 2007

Arthropod Management Tests ◽

10.1093/amt/33.1.e17 ◽

2008 ◽

Vol 33 (1) ◽

Author(s):

Paul McLeod

Keyword(s):

Sweet Corn ◽

Corn Oil ◽

Corn Earworm

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Ear Pests and Damage to Organic, Conventional and Bt-Protected Sweet Corn Grown in Central Kentucky

Journal of Entomological Science ◽

10.18474/0749-8004-44.4.383 ◽

2009 ◽

Vol 44 (4) ◽

pp. 383-390

Author(s):

John D. Sedlacek ◽

Karen L. Friley ◽

Steve L. Hillman

Keyword(s):

Helicoverpa Zea ◽

European Corn Borer ◽

Sweet Corn ◽

Crop Protection ◽

Fall Armyworm ◽

Corn Earworm ◽

Genetically Engineered ◽

Corn Borer ◽

Sap Beetles ◽

Southwestern Corn Borer

Sweet corn (Zea mays L. var. rugosa) was grown in replicated plots in 2004 and 2006 using organic, conventional, and genetically-engineered (Bt) production practices. Organic plots were treated with Entrust® (Dow AgroSciences LLC, Indianapolis, IN) whereas conventional and Bt sweet corn plots were treated with Warrior® (Syngenta Crop Protection, Inc., Greensboro, NC). All plots were treated once at silk emergence. Organic and conventional plots were treated again 1 wk later. Twenty-five ears were harvested from row centers in each treatment subplot to quantify ear pests and assess ear damage. The highest number of corn earworm, Helicoverpa zea (Boddie), larvae were found on organically-grown sweet corn. European corn borer, Ostrinia nubilalis (Hübner); southwestern corn borer, Diatraea grandiosella Dyar; and fall armyworm, Spodoptera frugiperda (J.E. Smith), larvae were not found as frequently. Neither corn earworm nor European corn borer larvae were found on Bt sweet corn ears. Sap beetles, Carpophilus lugubris Murray, were found on all 3 types of sweet corn. Organically and conventionally-grown sweet corn had a greater number of tip-damaged ears and numbers of damaged kernels per ear than Bt sweet corn. Ear length and weight were the same for all 3 types of sweet corn. Based on the information generated in this study, growing late-planted sweet corn organically or conventionally on a large commercial scale with a limited spray program and without using other types of ear pest management does not appear to be a practical or profitable option in central Kentucky.

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Combining Ability of Husk Extension, Maysin Content, and Corn Earworm Resistance

Journal of the American Society for Horticultural Science ◽

10.21273/jashs04974-20 ◽

2021 ◽

Vol 146 (1) ◽

pp. 14-23

Author(s):

Virginia M. Moore ◽

William F. Tracy

Keyword(s):

Zea Mays ◽

Combining Ability ◽

Helicoverpa Zea ◽

Sweet Corn ◽

Corn Earworm ◽

Management Options ◽

Mating Design ◽

Cultivar Development ◽

Factorial Mating ◽

Factorial Mating Design

Corn earworm (Helicoverpa zea) is a destructive pest with limited management options in sweet corn (Zea mays) production. Increased husk extension and the presence of the C-glycosyl flavone maysin are two proposed mechanisms for improving corn earworm resistance in corn cultivars. A factorial mating design was conducted to test hybrid combinations of sweet corn inbreds with long husks and/or maysin to identify candidates for future cultivar development. The mating design had seven male parents, including three commercial sweet corn inbreds (Wh9261, We11401, and Wt1001) and four inbreds selected for maysin content (Maysin1, 2, 3, and 4), and five female parents, including two commercial sweet corn inbreds (Ia453su and Ia5125su) and three inbreds with long, thick, tight husks (A684su, A685su, and A686su). Hybrids were evaluated for ear length, husk length, maysin content, and corn earworm resistance at six environments in 2016 and 2017. Relationships between husk extension, maysin, and corn earworm resistance were inconsistent, but five inbreds produced hybrids with significantly lower corn earworm infestation and/or damage, demonstrating potential to confer resistance to the corn earworm.

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Evidence for Decreasing Helicoverpa zea Susceptibility to Pyrethroid Insecticides in the Midwestern United States

Plant Health Progress ◽

10.1094/php-2007-0719-02-rv ◽

2007 ◽

Vol 8 (1) ◽

pp. 57 ◽

Cited By ~ 5

Author(s):

W. D. Hutchison ◽

E. C. Burkness ◽

B. Jensen ◽

B. R. Leonard ◽

J. Temple ◽

...

Keyword(s):

United States ◽

Helicoverpa Zea ◽

Sweet Corn ◽

Survival Rates ◽

Field Tests ◽

Corn Earworm ◽

High Survival ◽

Vegetable Crops ◽

Pyrethroid Insecticides ◽

Midwestern United States

The corn earworm (CEW), Helicoverpa zea (Boddie), is a highly mobile pest of numerous field and vegetable crops in much of North America. In the Midwestern United States, CEW is a voracious pest of several high-value vegetable crops, including sweet corn, tomatoes, and snap beans, and seed corn grown for the field corn industry. Historically, synthetic pyrethroid insecticides have been cost-effective and have provided excellent control of CEW, with control of larvae in sweet corn exceeding 90%. However, since 2000 pyrethroids have only provided 35 to 45% control in field tests conducted in the Midwest, as indicated by small-plot sweet corn efficacy trials. During 2005, the four most commonly used pyrethroids averaged only 19.3 to 37.3% control of CEW (mean of 5 trials in Minnesota, Wisconsin, Illinois, and Indiana). In addition, the survival of moths exposed to the standard pyrethroid, cypermethrin, using the Adult Vial Test (AVT), indicated high survival rates (44 to 66% at 5 μg cypermethrin and up to 45% survival at 10 μg). These levels are similar to, or higher than recent AVT results from Louisiana and Texas. These states reflect two possible “source” regions of late-season CEW that likely migrate north to the Midwestern states each summer. These results, including the stability of resistance each year in the Midwest, are discussed within the context of developing and expanding a North American resistance monitoring and management network. Accepted for publication 3 June 2007. Published 19 July 2007.

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Maize silk antibiotic polyphenol compounds and molecular genetic improvement of resistance to corn earworm (Helicoverpa zea Boddie) in sh2 sweet corn

International Journal of Plant Biology ◽

10.4081/pb.2010.e3 ◽

2010 ◽

Vol 1 (1) ◽

pp. 3 ◽

Cited By ~ 3

Author(s):

Baozhu Guo ◽

Ana Butrón ◽

Brian T. Scully

Keyword(s):

Helicoverpa Zea ◽

Sweet Corn ◽

Gene Action ◽

Molecular Genetic ◽

Pleiotropic Effect ◽

Corn Earworm ◽

Critical Factors ◽

Polyphenol Compounds ◽

Field Corn ◽

Antibiotic Compounds

The flavor of sh2 super-sweet corn is preferred by consumers. Unfortunately, sh2 sweet corn has little genetic variation for insect resistance. In this paper we review the functions of two loci, p1 and a1. The P1 allele has a major role in sh2 sweet corn resistance to corn earworm, an allele that was lost in historical selection because of its pleiotropic effect on undesirable cob color and silk browning. The P1 allele has significant effects on biosyntheses of silk antibiotic compounds, maysin, apimaysin, methoxymaysin, and chlorogenic acid. The effect of a1 shows gene action for lowered maysin and significant epistatic action with p1. The dominant functional allele A1 causes anthocyanin pigments in aleurone, plant, and pericarp tissues; the recessive a1 allele causes absence of pigment in these tissues. If silk browning and cob color are critical factors for maysin production but lack the customer’s preference, then separating red cob and browning silk, which are controlled by the P1 allele, may be difficult if not impossible. One high silk maysin sh2 sweet corn germplasm, shrunken Zapalote Chico, has been released. There is some field corn germplasm with p1-wwr alleles, but the amount of antibiotic flavones and their potential as a donor need further investigation.

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Foliar Sprays of Bacillus Thuringiensis in Early Corn, 1996

Arthropod Management Tests ◽

10.1093/amt/22.1.122a ◽

1997 ◽

Vol 22 (1) ◽

pp. 122-123 ◽

Cited By ~ 1

Author(s):

Ruth V. Hazzard ◽

Mark A. Mazzola

Keyword(s):

New York ◽

Bacillus Thuringiensis ◽

Helicoverpa Zea ◽

Sweet Corn ◽

Corn Oil ◽

Food Grade ◽

Foliar Sprays

Abstract Sweet corn was planted 2 May in blocks of 4 rows by 25 feet. Each treatment was repeated 4 times in a RCB design. Blocks were separated by 15 feet. Insecticides were applied on 5, 11, and 18 Jul, beginning before tassels emerged. Biweekly treatments were also sprayed on 9, 16, and 22 Jul. ECB flights were monitored with two nylon Heliothis traps baited with a Trece’ pheromone lure (New York or Iowa strain). The CEW flight was monitored with a Heliothis trap with a Hereon Helicoverpa zea lure. Sprays were applied at 75 psi with a four row drop nozzle sprayer pulled (5 nozzles per row) behind a tractor. A hand held applicator delivered 0.5 ml per ear of a 1 ;20 mixture of Dipel ES and food-grade corn oil directly to the silks on 16 Jul. Plots were harvested on 29 Jul. Fifty ears per plot were rated for damage, and for presence of CEW and ECB. Two ratings are reported; Undamaged ears = no feeding on ear; undamaged kernels = no feeding on filled kernels, may have feeding on unfilled tip.

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