Implementing a Cabbage IPM Program

Bill Hutchison and Eric Burkness, Department of Entomology, University of Minnesota, and Gary Pahl, Pahl's Farms, Inc., Apple Valley, Minnesota

Situation

Cabbage and broccoli continue to be important vegetable crops for Midwest growers, for both processing and fresh-market. Although the total acreage in Minnesota is relatively low (1,250 acres), the annual value to fresh-market producers ($3,800/ac), exceeds $4,750,000. During the past 10 years, the cabbage looper has been the most difficult insect pest to control, with imported cabbageworm and diamondback moth also complicating Integrated Pest Management (IPM) decision-making. The high cash value for these crops, combined with severe insect pressure, results in high insecticide use. Most growers continue to apply 5-8 insecticide applications annually, for mid- and late-season cabbage.

Five years of small-plot research showed that new infestation levels that require treatment (action thresholds) and sampling methods, based only on the presence or absence of larvae, could be used to quickly estimate pest densities, and to treat insect infestations. A new biologically-based insecticide, derived from the Actinomycete bacterium, Saccharopolyspora spinosa (SpinTor; Dow AgroSciences), was also shown to provide consistent control of cabbage looper, with minimal impact on the diversity of natural enemies (predators and parasitoids), which are important for regulating other caterpillar and aphid pests.

Action Taken

Despite positive results from Experiment Station research, few growers were willing to quickly implement the new IPM strategies on a large scale. Beginning in 1998, a new partnership was created between Gary Pahl, Pahl’s Market, Inc., and the Vegetable IPM Program of the University of Minnesota Extension Service, to initiate an “On-Farm Vegetable IPM Demonstration Project,” and develop a strategy for more wide-scale implementation. The first step was to demonstrate, in replicated on-farm trials, the benefits of a more focused IPM program in a large-scale commercial production system. The Partners were specifically interested in achieving one or more of the following outcomes: reduced number of insecticide applications, acceptable or improved at-harvest marketability (fresh-market) and yield. To conduct the study, Pahl’s Farms provided six commercial fields to evaluate the IPM program. In both years, an IPM approach was compared to both conventional grower practices, and untreated check plots.

Results

Results Cabbage looper and imported cabbageworm pressure was high in both years. However, the results of the IPM trial were very encouraging. Yields were not significantly different among the three management scenarios for either year, but cost of inputs was less. During 1998, the IPM approach required a total of 4 sprays (two with SpinTor) compared with 7 sprays (methomyl and pyrethroids) in the conventional plots. In 1999, the IPM plots only received one-third of the spray treatments (1 spray SpinTor, compared with 3 methomyl and pyrethroid sprays) in the conventional plots; and average reduction in sprays for both years was 54%. During both years, at-harvest larval contaminants were significantly lower for both the IPM and conventional plots, compared with the untreated check plots. In addition, for both years, marketability reflecting minimal damage to the head and wrapper leaves for the IPM plots was significantly higher than those from the conventional and untreated check plots. These results demonstrate the first step to IPM implementation, with this program, i.e., on-farm validation of IPM with a leading grower. Future steps include: timely delivery of research-based results to other growers at winter educational meetings, demonstrations to other growers at field days, and presentations to growers by the participating grower (Gary Pahl).

Grower’s Viewpoint

“The biggest thing I learned from this project is the importance of scouting and timing of applications. Anytime you can get by with one spray (1999), it saves the grower a lot of money. It also shows the importance of regular scouting; we usually just scout to determine the first spray, and then go on a calendar-based schedule after that. But regular scouting will probably save us more money in the long-term.” (Gary Pahl, Pahl’s Farms, Inc., October, 1999)

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

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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.