Insecticidal Control of Lepidopteran Pests in Cabbage

Eric C. Burkness, Patrick O'Rourke, and Bill Hutchison, Dept. of Entomology, University of Minnesota

This article represents the first in a series, to provide brief research summaries from current projects by University of Minnesota and Minnesota Extension Service staff.

Methods: Cabbage variety 'Morris' was transplanted 30 Jun at the University of Minnesota Agricultural Experiment Station at Rosemount, MN. Treatments were applied with a CO2 pressurized backpack sprayer using XR-Teejet 8002 flat fan, with no screen, nozzles. Dyne-Amic surfactant was added to all treatments, except the Mycotrol treatments, at a rate of 0.64 fl oz/gal (5.0 ml/liter). (Mycotrol (Mycotech Corp. Butte, MT) is a commercially available form of the parasitic fungus Beauveria bassiana). Four applications were made 27 Jul and 3, 11, and 19 Aug. Treatments were evaluated for larval infestation of imported cabbageworm (ICW), cabbage looper (CL), and diamondback moth (DBM), 10 and 24 Aug. All larval counts were taken from the middle row of each plot.

Plots were harvested 25 Aug. In each treatment, 2 sets of 5 consecutive heads, with 4 wrapper leaves on each head, were harvested from the middle row and evaluated for feeding damage using Green's rating scale (J. Econ. Entomol. 1969 62: 798-800), where: 1=no feeding damage; 2=minor feeding damage on the wrapper leaves (0-1% eaten) with no head damage; 3=moderate feeding damage on the wrapper leaves (2-5% eaten) with no head damage; 4=moderate feeding damage on the wrapper leaves (6-10% eaten) and minor feeding scars on the head; 5=moderate to heavy feeding on the wrapper leaves (11-30% eaten) and moderate feeding scars on the head; 6=greater than 30% of the wrapper leaves eaten and numerous feeding scars on the head. The number of larval contaminants within the 4 wrapper leaves and head were also noted.

Results: Preliminary larval counts were taken 26 Jul. Preliminary counts revealed an average of 0.25 small ICW, 0.08 ICW pupae, 2.9 small CL, 0.33 medium CL, 0.08 large CL, 0.08 CL pupae and 2.34 total DBM per 10 heads. Dominant insect pests were ICW and CL. The first sample on 10 Aug was taken after 2 applications and the second sample was taken on 24 Aug after 4 applications. For both sample dates, all treatments performed significantly better than the untreated check for ICW and DBM except for the low rate of Mycotrol / Dipel on DBM on the first sample date. For both sample dates, all treatments provided significant control for total CL. However, for the first sample date, all products provided significant control except for Mycotrol / Dipel and Dipel treatments on small CL, lower rates of Mycotrol / Dipel and Dipel on medium CL, and higher rates of Mycotrol / Dipel and Dipel on large CL. On the second sample date, all treatments provided significant control of CL except for Mycotrol / Dipel and Dipel treatments on small CL and low rates of Mycotrol / Dipel on medium CL. Compared to the check, all treatments significantly improved marketability and significantly reduced the incidence of larval contaminants. No phytotoxicity was observed.

See table for detailed results.

For more information or questions contact Eric Burkness (612) 624-3670.

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 11, 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.