In this Issue:
Sweet Corn Insecticide Trial Results
| Vol 5 No. 8 | September 12, 2003 |
European Corn Borer Control in Minnesota Sweet Corn, 2003
E.C. Burkness, R.L. Koch, and W.D. Hutchison, Department of Entomology, University of Minnesota
Each year we conduct insecticide
trials for major vegetable insect pests in Minnesota. Here, we present the
results of our 2003 study with European corn borer (ECB) in sweet corn.
In addition to several standard insecticides, we had the opportunity to
evaluate “Entrust”, a recently approved insecticide for organic
growers. The active ingredient (spinosyns) is identical to that of
SpinTor--approved for conventional growers on a variety of crops.
The sweet corn variety ‘Jubilee’ was planted May 16 at the University of Minnesota Research and Outreach Center at Rosemount, MN. Plots were arranged in a randomized complete block design with 3 replications. Plots consisted of 2 rows 25 ft (7.6 m) long with 30 in (0.8 m) row spacing with a single skip row separating treatments and 10 ft alleys (3.04 m) separating replicates. Treatment applications were made using a CO2 pressurized backpack sprayer with a two-nozzle 3 foot boom and XR-Teejet 8002 flat fan nozzles with no screens. The sprayer was calibrated to deliver 25 gpa (233.8 l/ha) at 35 psi (242 kPa). Plots were artificially infested with ECB on July 25. Approximately 25 neonate larvae per ear were placed on 30 primary ears per plot (15 primary ears per row) using a bazooka applicator. The ear zone of each row of the 2-row plot was treated beginning at < 5% silk. A total of 3 applications were made on the following dates, July 22 and 28, and August 4. Twenty-five primary ears per plot were harvested and evaluated August 15. Total number of ECB larvae, larval size and location, and feeding damage (cm2) were recorded.
Average ECB larval density was 0.44 per ear in the untreated check (see Table, below). All treatments provided significant control of ECB compared to the untreated check (for total ECB) and all treatments provided significant control of large ECB. Percentage of marketable ears for fresh market and processing was significantly higher for all treatments compared to the untreated check. Kernel feeding damage was significantly lower in all treatments compared to the untreated check. Although SpinTor and Entrust provided the highest level of control, numerically, these products are currently too expensive for most growers. Most of the pyrethroids provided good ECB control. However, when accounting for kernel damage, and the impact on marketability, some of the pyrethroids did not perform as well. Phytotoxicity was not observed among the treatments.
| Table 1: Evaluation of insecticides for control of European corn borer in Minnesota sweet corn, 2003 | ||||||
| Treatment/formulation | Rate lb(AI)/ac | Mean number of ECB/eara | Mean number of large ECB/earb | Fresh marketc | Processingd | Total kernel feeding damage/ear (cm2)e |
| SpinTor 2SC | 0.094 | 0.00 d | 0.00b | 99 a | 100 a | 0.03 b |
| Entrust 80WP | 0.094 | 0.00 d | 0.00 b | 97 ab | 100 a | 0.07 b |
| Warrior 1 CS | 0.02 | 0.05 cd | 0.05 b | 92 abc | 93 cd | 0.19 b |
| Warrior 1 CS | 0.025 | 0.05 cd | 0.04 b | 95 abc | 96 abcd | 0.10 b |
| Capture 2EC | 0.04 | 0.08 bcd | 0.05 b | 87 bc | 95 abc | 0.47 b |
| Capture 2EC/Mustang Max 0.8 EC/Mustang Max 0.8EC | 0.0.4/0.025/0.025 | 0.03 d | 0.01 b | 95 abc | 99 ab | 0.11 b |
| Proaxis | 0.025 | 0.07 bcd | 0.05 b | 914 bc | 95 bcd | 0.29 b |
| Mustang Max 0.08EC | 0.025 | 0.15 bc | 0.07 b | 88 bc | 93 cd | 0.21 b |
| Pounce 3.2EC | 0.2 | 0.16 b | 0.09 b | 87 c | 89 d | 0.56 b |
| Untreated Check | -- | 0.44 a | 0.28 a | 59 d | 75 e | 1.55 a |
| Means within columns
followed by the same letter are not significantly different (P > 0.05),
Least significant difference Test (LSD). Mean percentage of marketable ears for
fresh market and processing were transformed using the arcsin transformation to
obtain mean separations using LSD (P=0.05); untransformed means are presented.
a Includes all ECB instars in the husk, silk, tip, side, butt, or shank of the ear. b Includes large (3rd - 5th instar) ECB in the tip, side, or butt of the ear. c Percentage of ears with no kernel damage or larvae present. d Percentage of ears with only small larvae (1-2 instar ECB) and/or damage limited to the tip; no damage or larvae on the side or butt of the ear. e Total kernel area damaged/ear in the tip, side, or butt by ECB. |
||||||
Co-Editors: Bill Hutchison, Department of Entomology,
University of Minnesota, hutch002@tc.umn.edu
Jeanne Ciborowski, IPM Program, Minnesota Department of Agriculture,
jeanne.ciborowski@state.mn.us
Production Editor: Suzanne Wold Burkness, Research Fellow, Department of
Entomology, University of Minnesota, woldx018@tc.umn.edu
Last Revised September 11, 2003.
The University, including the Minnesota Extension Service, is an equal
opportunity educator and employer. ©1999-2003 Minnesota Extension Service,
University of Minnesota. All rights reserved. Contact
copyright@extension.umn.edu
for information on reproduction or use of this material.