1998 Sweet Corn Insecticide Performance for Corn Earworm in MN

Patrick O’Rourke, Eric Burkness, and Bill Hutchison, Department of Entomology, University of Minnesota

Methods:

‘Jubilee’ was planted 6 Jul at the University of Minnesota Agricultural Experiment Station at Rosemount, MN. Plots were arranged in a RCB (randomized complete block) design with 4 replications. Plots were 2 rows, 25 feet (7.6 m) long, with 30 inch (0.8 m) row spacing. A single skip row separated treatments and a 10 foot alley (3.04 m) separated replications. Treatments were applied using a CO2 pressurized backpack sprayer using a single-nozzle wand fitted with a XR-Teejet 8002 flat fan nozzle and no screen. The sprayer was calibrated to deliver 20 gpa (187.04 l/ha) at 35 psi (242 kPa). Both rows of each 2-row plot were treated at the ear zone beginning at 50% silk. Four treatments were applied, 1,4,7, and 14 Sep. Treatments were evaluated 21 Sep by harvesting 25 ears at random from each plot (100 total ears per treatment) and recording the total number of larvae, larval size and feeding damage (cm2).

Results:

Corn earworm(CEW) was the primary pest in this study. Total CEW and European corn borer (ECB) larval density averaged 27.3 and 3.0 per 25 ears, respectively, in the untreated check. Pheromone trapping indicated first CEW arrival at Rosemount 29 Jul. Mean trap-catch per night was 8.8 CEW moths from first arrival to harvest, and 10.3 CEW moths from 50% silk to harvest. Maximum catch occurred 1 Sep at 49 CEW/trap. All treatments provided significant control of ECB compared with the untreated check. All insecticides, with the exception of Penncap-M and RH-2485 (both rates) provided significantly greater control of CEW, and a significantly greater number of marketable ears for fresh market than the untreated check. Early instar CEW larvae accounted for most of the total CEW for Baythroid (both rates), Pounce and Warrior (low rate). All insecticides, except RH-2485 (low rate), provided a significantly higher percentage of ears for processing than the untreated check. Kernel feeding damage was significantly lower in all treatments compared to the untreated check. No phytotoxicity was observed among treatments.

Please see table 1 for detailed results.

In future issues, composite analyses (multiple years) of insecticide efficacy data for European corn borer and corn earworm in the Midwest will be presented.

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, Research Specialist, University of Minnesota, woldx018@tc.umn.edu

Disclaimer
Reference to products in this publication is not intended to be an endorsement to the exclusion of others which may have similar uses. Any person using products listed in this publication assumes full responsibility for their use in accordance with current directions of the manufacturer

Last Revised November 19, 1999.
The University, including the Minnesota Extension Service, is an equal opportunity educator and employer.©1999 Minnesota Extension Service, University of Minnesota. All rights reserved. Contact copyright@extension.umn.edu for information on reproduction or use of this material.