Managing pesticide resistance

The complexity of crop production decision-making is escalated by issues that have Iowa farmers concerned about pesticide resistance. How to better manage weed, insect and disease resistance was one of the topics discussed at the Iowa State University tent at the 2014 Farm Progress Show. Farmers met and talked about this issue with researchers and Extension specialists working in the area of

Managing pesticide resistance

The complexity of crop production decision-making is escalated by issues that have Iowa farmers concerned about pesticide resistance. How to better manage weed, insect and disease resistance was one of the topics discussed at the Iowa State University tent at the 2014 Farm Progress Show. Farmers met and talked about this issue with researchers and Extension specialists working in the area of crop pest resistance.

There is much to consider when making management decisions in production agriculture including the pesticide resistance of target pests: weeds, insects, plant pathogens and nematodes. The complexity of crop production decision-making is escalated by frogeye leaf spot, the arrival of Palmer amaranth, and corn rootworm resistance — a few of the issues that concern farmers about pesticide resistance.

An ISU team of researchers and Extension specialists (the Integrated Cropping Systems Team) is addressing how farmers can best manage the issue of pesticide resistance. The team is concerned about current and potential resistance issues and related management practices. The team includes agronomists, entomologists, plant pathologists, microbiologists, weed scientists and a climatologist.

Insect issues discussed

At the show, farmers who visited with ISU crop specialists were concerned about problems with corn rootworms developing resistance to Bt rootworm corn hybrids. Erin Hodgson, ISU Extension entomologist and associate professor of entomology, is a crops team leader and describes resistance as “the decreased susceptibility of a pest to a management strategy.” Often, resistance is associated with pesticides, but it could include cultural control (such as crop rotation) and host plant resistance (such as Bt traits for insects).

“When it comes to insects, they are always trying to evolve to be more competitive,” says Hodgson. “Eventually, insects will overcome our standard management tactics. Some, like western corn rootworm, just do it faster than most.”

Weed resistance problems

Weeds with resistance to herbicides were first found in the 1950s. Now that Palmer amaranth has arrived in five Iowa counties, along with its history of resistance in other states, herbicide resistant weeds are getting more attention.

Bob Hartzler, ISU agronomy professor and Extension weed scientist, says the solution to managing the situation is simple: Farmers must stop doing what they are doing and take different actions. Hartzler is referring to farmers spraying glyphosate year after year on fields planted with seeds that are genetically engineered to tolerate this herbicide. They need to use different weed control tactics.

“Start deploying more diverse weed management strategies that incorporate some combination of crop rotation, cover crops, manual tillage and a broader range of herbicides. Farmers need to become less dependent on glyphosate,” he says.

Diseases and IPM

Daren Mueller, ISU Extension soybean pathologist and coordinator of the Integrated Pest Management program at Iowa State, says pesticide resistance results from using the same pesticide repeatedly. When resistant weeds, insects and fungi are present, Mueller says a biotype of an organism has survived exposure to a pesticide that would normally kill an individual of that species. Resistance can be managed several ways so that pesticides remain a useful way of controlling pest organisms.

“Only apply pesticides when needed. Scout your fields to determine pest populations present and only use pesticides when the economic thresholds are met. And always follow label directions,” Mueller advises. “Rotate types of pesticides when you use them during the year and from year to year, too. And use alternative management options, such as production practices, natural enemies, crop resistance and crop rotation.”

Scouting and pest identification guides are available from the Extension Online Store at store.extension.iastate.edu/ProductList?Keyword=CSI.

Source: Iowa State University

This article published in the September, 2014 edition of WALLACES FARMER.

All rights reserved. Copyright Farm Progress Cos. 2014.

IPM

Pest Control

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