Neb.: pest resistance workshops in March |

Neb.: pest resistance workshops in March

Nebraska Extension will conduct workshops this March in Scottsbluff and three other locations to inform ag producers and others about the importance of managing herbicide, insecticide and fungicide resistance, understanding mode of action, and reducing the potential for resistance in weeds, insects and plant pathogens.

The Scottsbluff workshop is scheduled for March 11 from 9:30 a.m. until 2:30 p.m. in the Bluestem Room at the Panhandle Research and Extension Center. Other workshops are scheduled for March 7 in Wayne, March 8 in Clay Center and March 10 in Grant.

Preregistration will be conducted on-line at That web page contains a hyperlink to register for the Scottsbluff workshop. The cost of the workshop material is $50.

Continuing education credits for Certified Crop Advisors have been applied for, or can be self-reported.

For more information contact Extension Educator Gary Stone at the Scottsbluff office (308-632-1480,, or Dr. Stevan Knezevic, specialist at UNL’s Haskell Ag Laboratory at Concord (, or Wendy Winstead (

The five-hour workshop includes presentations on insect resistance; disease resistance; herbicide-tolerant crops; herbicide mode of action and site-of -action groupings; how weed resistance develops; and weed resistance in the Midwest and Nebraska. Workshop attendees will also take part in a hands-on exercise on controlling major multiple resistant weed species.

Speakers are members of the UNL weed science, entomology and plant pathology teams, including Stevan Knezevic (lead), Amit Jhala, Cody Creech, Nevin Lawrence, Chris Proctor, Keth Jarvi, Bob Right, Julie Peterson, Jeff Bradshaw, Tamra Jackson-Ziems, Antony O.Adesemoye, Sarah Schlund and Robert Harveson.

Weed, disease, and insect resistance to herbicides, insecticides, and fungicides is not new. In fact, pest resistance to any pest management tool, tactic or strategy has been documented from nearly the time when humans began cultivating plants. In the mid-1950s, weed scientists predicted that repeated use of any herbicide could lead to shifts in weed species composition within a weed community and that herbicide tolerance in weeds could quickly increase with repeated use of the same herbicide.

By the early 1970s the first cases of weed resistance occurred in pigweed species showing resistance to atrazine. Today, about 368 herbicide-resistant weed biotypes worldwide are reported to be resistant to 19 different herbicide modes of action. For example, 55 species are known to have biotypes resistant to triazine herbicides, and at least 50 weed species have been reported to have biotypes resistant to one or more herbicide families.

Repeated use of the same herbicide was always the main reason for weed resistance to herbicides worldwide.

Insects have shown a similar pattern in developing resistance to many types of insecticides used to control crop pests. Insecticide resistance is a global issue for a wide variety of agriculturally important pests and has been reported in over 540 insect and mite species.

Nebraska has had a long history with insecticide-resistant pests. The western corn rootworm has been particularly difficult and has developed resistance to numerous insecticides for both larval and adult controls. In addition, corn rootworm in parts of Nebraska and the Midwest have developed resistance to some of the Bt proteins found in genetically modified corn, leaving growers with fewer control options and greater management costs.

In the United States, crop losses due to pesticide resistance are estimated at $1.4 billion annually.

Plant pathogens have not shown significant development of resistance to fungicides for the most common diseases in field crops. However, there are some resistance issues and the increased use of fungicides may lead to more.

Currently, Frogeye Leaf Spot of Soybean and Fusarium Head Blight of Wheat are the only diseases known to have fungicide resistance in U.S. corn, soybean and wheat crops, but have not been identified in Nebraska yet. Among specialty crops grown in Nebraska there is fungicide resistance in Ascochyta Blight of Chickpeas.

Fungicides are still a primary mean of controlling plant diseases, and many companies are developing products with multiple modes of action as a means of providing more durable products and manage resistance development.

–UNL Extension

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