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

2004 ◽  
Vol 14 (3) ◽  
pp. 307-314 ◽  
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.

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

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.

Mortality of Two Lepidopterans in Response to Selected Commercial Formulations of Bacillus thuringiensis Berliner2

1999 ◽  
Vol 34 (3) ◽  
pp. 273-285
Author(s):  
Richard L. Ridgway ◽  
Robert R. Farrar
Keyword(s):  
Bacillus Thuringiensis ◽  
Helicoverpa Zea ◽  
European Corn Borer ◽  
Uv Light ◽  
Field Studies ◽  
Corn Earworm ◽  
The Other ◽  
Speed Of Kill ◽  
Matrix Formulation ◽  
Corn Borer

Five commercial granular formulations of Bacillus thuringiensis Berliner marketed for controlling the European corn borer, Ostrinia nubilalis (Hübner), were compared for insecticidal activity using treated discs of bean leaves. Three formulations, Dipel 10G®, Full-Bac ECBG™, and Strike BT®, were similar in terms of both mortality and speed of kill. A formulation containing a strain of B. thuringiensis developed by plasmid fusion, Condor G®, caused mortality similar to the other three formulations, but the speed of kill was slower. A fifth formulation containing a B. thuringiensis toxin produced by Pseudomonas fluorescens Migula as result of a gene transfer, M-Peril™, caused substantially less mortality than any of the other formulations. An experimental water dispersible formulation, based on a previously developed granular matrix formulation containing B. thuringiensis and a nutrient-based phagostimulant, caused significantly higher mortality of the European corn borer than a similar formulation without the phagostimulant. Simulated field studies were conducted to study the effects of the phagostimulant on feeding and protection of B. thuringiensis from ultraviolet (UV) light. Bean plants treated with B. thuringiensis and the phagostimulant were exposed to different UV regimes outdoors under canopies made of specialized acrylic plastics and then infested with larvae of the corn earworm, Helicoverpa zea (Boddie). A significant interaction between the UV regimes and the phagostimulant was found, indicating that the phagostimulant acted both as a feeding stimulant and as a UV protectant to enhance the activity of B. thuringiensis.

Enhancement of Activity of Bacillus thuringiensis Berliner Against Four Lepidopterous Insect Pests by Nutrient-Based Phagostimulants1

1995 ◽  
Vol 30 (1) ◽  
pp. 29-42 ◽  
Author(s):  
Robert R. Farrar ◽  
Richard L. Ridgway
Keyword(s):  
Bacillus Thuringiensis ◽  
Ostrinia Nubilalis ◽  
Helicoverpa Zea ◽  
European Corn Borer ◽  
Insect Pests ◽  
Diamondback Moth ◽  
Lethal Dose ◽  
Corn Earworm ◽  
Corn Borer ◽  
Whole Plants

To help improve control of insect pests with microbial insecticides, we investigated the interactions of four commercial, nutrient-based phagostimulants (Pheast [AgriSense], Coax [CCT Corp.], Gusto [Atochem North America, Inc.], and Entice [Custom Chemicides] with Bacillus thuringiensis Berliner and four lepidopterous insect pests (gypsy moth, Lymantria dispar [L.] [Lymantriidae]; corn earworm, Helicoverpa zea [Boddie] [Noctuidae]; European corn borer, Ostrinia nubilalis [Hübner] [Pyralidae]; and diamondback moth, Plutella xylostella [L.] [Plutellidae]). Comparisons were made of treated foliage in Petri dishes in the laboratory and of sprayed whole plants in a greenhouse. In general, phagostimulants increased mortality of all species tested, but no consistent differences among phagostimulants were found for any species. Food consumption was generally lower on the treatments that contained phagostimulants causing the highest rates of mortality, possibly as a result of more rapid ingestion of a lethal dose on these treatments. Reduced rates of feeding by insects on treatments with B. thuringiensis alone were seen, probably due in part to intoxication and, possibly, to behavioral effects as well. Indications of potentially significant interactions between host plants and both B. thuringiensis and phagostimulants also were seen.

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

2003 ◽  
Vol 13 (3) ◽  
pp. 509-514 ◽  
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.

scholarly journals Recurrent Full-sib Family Selection for Husk Extension in Sweet Corn

2019 ◽  
Vol 144 (1) ◽  
pp. 63-69 ◽  
Author(s):  
Virginia M. Moore ◽  
William F. Tracy
Keyword(s):  
Helicoverpa Zea ◽  
European Corn Borer ◽  
Recurrent Selection ◽  
Sweet Corn ◽  
Corn Earworm ◽  
Direct Selection ◽  
Initial Population ◽  
Family Selection ◽  
Corn Borer ◽  
Selection For

Corn earworm (Helicoverpa zea) is a costly and destructive pest in sweet corn (Zea mays) production. A recurrent selection experiment was conducted to assess the feasibility of selecting a sweet corn population for longer husks without shortening the ears and to determine whether direct selection for longer husks confers improved resistance to the corn earworm. The initial population was derived from crosses between long- and tight-husked inbred lines (A684su, A685su, and A686su) originally selected for resistance to the european corn borer (Ostrinia nubilalis) and a high-quality commercial hybrid parent (‘Super Sweet Jubilee Plus’). Three cycles of recurrent full-sib family selection were conducted from 2014 to 2016, with a selection intensity of ≈10% per cycle. In 2017, the cycles of selection were evaluated and compared with common commercial cultivars for husk extension, ear length, rate of corn earworm infestation, and extent of corn earworm damage. Ears were artificially infested with corn earworm eggs suspended in an agar solution. The population was successfully selected for longer husk extension without shortening the ears, but the increase in husk extension did not correspond to an increase in corn earworm resistance. Further evaluation is needed to determine whether long husk extension is ineffective as a source of corn earworm resistance, whether it is more effective in combination with other resistance traits, whether greater differences in husk extension are needed to confer biologically significant differences in corn earworm resistance, or whether improved inoculation methods could improve differentiation between genotypes.

scholarly journals CONTROL OF CORN EARWORM AND EUROPEAN CORN BORER ON SWEET CORN, 1998

1999 ◽  
Vol 24 (1) ◽  
Author(s):  
P. K. O'Rourke ◽  
E. C. Burkness ◽  
W. D. Hutchison
Keyword(s):  
European Corn Borer ◽  
Sweet Corn ◽  
Corn Earworm ◽  
Corn Borer

scholarly journals Evaluation of Efficacy of Selected Conventional and Experimental Insecticides and Bt Hybrids for Control of Corn Earworm and European Corn Borer on Sweet Corn, 1997

1998 ◽  
Vol 23 (1) ◽  
pp. 99-100
Author(s):  
J. T. Shaw ◽  
R. Weinzierl ◽  
J. W. Finger
Keyword(s):  
European Corn Borer ◽  
Sweet Corn ◽  
Corn Earworm ◽  
Compressed Air ◽  
Hollow Cone ◽  
Corn Hybrids ◽  
Corn Borer ◽  
Chemical Treatments ◽  
Untreated Check ◽  
High Clearance

Abstract The tests were arranged in a RCB design with four replications. Each plot consisted of four rows, each being 30 inches wide and 50 ft long. Thirty-foot-wide alleys were established between the four replications. Insecticides were applied to the middle two rows of each plot, leaving two untreated rows between adjoining plots. Twelve insecticide treatments were compared with two Br-sweet corn hybrids (Heritage Bt and Bonus Bt) and their non-Bt isolines to two untreated controls. The 12 chemical treatments and the two untreated checks were planted with the Silver King variety sweet corn. Two untreated check plots were included in each replication and were averaged for the ANOVA. Treatments were applied very four to five days beginning on 8 Aug at 8% silk. All insecticide treatments were applied with a modified John Deere 6000 high-clearance vehicle (HCV) with a rear-mounted boom. Six Conejet (TX VS-8) hollow-cone nozzles (three per row) were calibrated to deliver 30.1 gpa at 40 psi and a speed of 2.5 mph, utilizing a compressed air system. Four nozzles (two per row) were attached to drops and directed the spray towards the ear zone area, a third nozzle (one per row) was mounted directly over the row with the spray being directed into the whorl (tassel) area.

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

2007 ◽  
Vol 17 (2) ◽  
pp. 163-168 ◽  
Author(s):  
Tori Lee Jackson ◽  
Mark G. Hutton ◽  
David T. Handley
Keyword(s):  
New England ◽  
Helicoverpa Zea ◽  
Sweet Corn ◽  
Corn Oil ◽  
Corn Earworm ◽  
Soy Oil ◽  
Conventional Management ◽  
Repeated Applications ◽  
Materials Used ◽  
Significant Injury

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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