In this Issue:
VEGETABLE NEWS
Summary of Corn Earworm and European Corn Borer Dynamics in 2007
Insecticide Efficacy for Corn Earworm: Small-Plot Trial 2007
BERRY NEWS
APPLE NEWS
2007 Trap Catches for Codling Moth and Dogwood Borer at 5 Apple Orchards Monitored by the MDA
Minnesota Department of Agriculture’s 2007 Exotic Apple Insect Pest Survey
| Vol 4 No. 12 | September 28, 2007 |
Insecticide Efficacy for Corn Earworm: Small-Plot Trial 2007
Eric Burkness & Bill Hutchison, Dept. of Entomology, St. Paul, Minn.
Providence sweet corn was planted on June 20th at the University of Minnesota Research and Outreach Center at Rosemount, MN. Plots were arranged in a randomized complete block (RCB) design with four replications. Plots consisted of two rows that were 25 feet long with 30 inch row spacing with a single skip row separating treatments and 10 foot alleys separating replicates. The seeding rate was approximately 26,000 seeds/acre. Treatment applications were made using a CO2 pressurized backpack sprayer with a 3 foot, 2-nozzle boom and XR-Teejet 8002 flat fan nozzles with no screens. The sprayer was calibrated to deliver 25 gpa at 35 psi. The ear zone of each row of the 2-row plot was treated beginning at 50% silk. All treatments received a total of four applications on the following dates; August 13th, 17th, 23rd, and 29th, with the exception of the Capture 2 EC (spray 1, 2) Warrior 1 CS (spray 3) treatment, which was sprayed on August 13th, 21st, and 29th. Twenty primary ears per plot were harvested and evaluated September 7th. Total number of corn earworm (CEW) larvae, larval size and location, and total number of kernels with feeding damage were recorded.
Mean total CEW larval density on the ear was very high at 1.48 per ear in the untreated check (Table 1). All treatments provided a significant reduction in both late instar and total CEW larvae and damaged kernels compared to the untreated check. However, most treatments provided relatively poor control with the exception of Hero and the Bt sweet corn treatments that both provided 91% control of late instar larvae. All treatments dropped below 68% control for total CEW larvae, reflecting the continued exposure to high CEW pressure throughout the silking period. We primarily focus on control of late instar larvae and worry less about early instar larvae based on the ability of processing equipment to “process” out the early instar CEW. In addition, the larvae that make it to the final larval instar will consume on average between 10-14 kernels.
Note: We also conducted an application timing trial using Warrior, looking at different percentages of silking when applications are initiated and followed an approximate 3-day spray interval. The best control was 96 and 91% for late instar and total CEW control, respectively. The results from the application timing trial will be summarized and presented at upcoming meetings.
| Table 1. Small-plot insecticide trial results, CEW in late-planted sweet corn; Rosemount, MN. | ||||
xx |
Mean number larvae per ear |
xx | ||
Treatment |
Rate lb(AI)/ac |
Large CEW |
Total CEW |
Total damaged kernels/earc |
Capture 2 EC |
0.04 |
0.30 (76) bc |
0.84 (43) bcd |
3.21 b-e |
Capture 2 EC (spray 1, 2) Warrior 1 CS (spray 3, 4) |
0.10 / 0.03 |
0.20 (84) b-e |
0.48 (68) ef |
1.83 fgh |
BC 0805 Bt |
-- |
0.11 (91) def |
0.53 (64) ef |
0.99 hij |
Capture 2 EC (spray 1, 2) Warrior 1 CS (spray 3) |
0.10 / 0.03 |
0.25 (80) bcd |
0.50 (66) ef |
1.50 g-j |
Warrior 1 CS |
0.025 |
0.34 (73) bc |
0.70 (53) b-e |
3.03 c-f |
Warrior 1 CS |
0.03 |
0.33 (74) bc |
0.85 (43) bc |
3.70 bcd |
Mustang Max 0.8 EC |
0.025 |
0.33 (74) bc |
0.61 (59) c-f |
2.85 d-g |
Discipline + Lannate LV |
0.05 + 0.225 |
0.18 (86) c-f |
0.53 (64) ef |
1.79 fgh |
Warrior 1 CS + Lannate LV |
0.03 + 0.225 |
0.25 (80) bcd |
0.61 (59) c-f |
3.10 b-f |
Hero |
0.048 |
0.18 (86) c-f |
0.53 (64) ef |
2.58 d-g |
Hero |
0.058 |
0.11 (91) def |
0.58 (61) def |
1.56 ghi |
Delta Gold |
0.03 |
0.31 (75) bc |
0.93 (37) b |
4.29 bc |
Untreated Check |
-- |
1.25 (--) a |
1.48 (--) a |
13.01 a |
| Means within columns followed by the same letter are not significantly different (P > 0.05), Protected Least significant difference Test (LSD). Mean percentage of marketable ears for fresh market and processing were transformed using the arcsine transformation to obtain mean separations using LSD (P=0.05); untransformed means are presented. aIncludes CEW that are 3rd-6th instar in the tip, side, or butt of ear. b Includes all CEW instars in the tip, side, or butt of the ear. cTotal kernels damaged/ear in the tip, side, or butt by ECB and/or CEW. |
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ACKNOWLEDGEMENTS
Co-Editors: Bill Hutchison (hutch002@umn.edu), Department of Entomology, University of Minnesota, Jeanne Ciborowski, Minnesota Department of Agriculture, Ag. Resources Management and Development Division, and Suzanne Wold-Burkness (woldx018@umn.edu), Department of Entomology, University of Minnesota
The Newsletter is published weekly from May through August, cooperatively, by the Minnesota Department of Agriculture (MDA) and the University of Minnesota (U of MN). Reports are posted on the U of MN and MDA web sites on Fridays. If you have suggestions and/or comments, please send your contributions by 4 p.m., Wednesday to Jeanne Ciborowski, 651-201-6217, jeanne.ciborowski@state.mn.us , MDA, 625 Robert St. North, St. Paul, MN 55155. You can access the Newsletter at the U of MN web site in htm format at: www.vegedge.umn.edu/MNFruit&VegNews/mnindex.htm and at the MDA web site in pdf format at: www.mda.state.mn.us/plants/pestmanagement/ipm/ipmnews.htm
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Last Revised September, 2007 by woldx018@umn.edu
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