2014-15 Rapid Ag: Insecticide Resistance Management in MN Soybean

December 5, 2014

Principal Leader

Robert Koch

Department

Entomology

Funding Awarded

2014 Fiscal Year: $64,884

2015 Fiscal Year: $62,579

The Problem

Pesticide resistance management is critical to the sustainable management of pests and preservation of key crop protection chemicals as tools for integrated pest management (IPM). The threat of development of resistance of aphids, mites and stink bugs in soybean to limited effective and labeled insecticide classes creates an urgent need for both new research and an educational (Extension) response. Research is needed to determine efficacy and regional patterns of susceptibility and to develop a resistance management plan for soybean arthropods incorporating recent observation on resistance and Extension efforts are needed to communicate this plan.

Background

The soybean aphid, Aphis glycines (hereinafter referred to as aphid), is the most significant arthropod pest of soybean in the U.S. causing up to 40% yield loss. The invasion of this aphid has resulted in increased use of insecticides in soybean. Over a ten-year period, insecticide use in soybean increased 130 fold.

Advances have been made in integrated pest management (IPM) for aphids in soybean (e.g., sampling plans, economic thresholds, host plant resistance and biological control). However, suppression of aphid outbreaks still depends on the use of a limited number of broad-spectrum insecticide classes (modes of action), (i.e., organophosphates, pyrethroids and neonicotinoids). The repetitive and sometimes inappropriate use of these insecticides creates a situation ripe for development of insecticide resistance in aphids and secondary pests, such as the two-spotted spider mite, Tetranychus urticae (hereinafter referred to as mite).

Resistance is currently developing in Minnesota. Drought conditions in 2012 prompted outbreaks of mites in soybean producing areas across the state. Currently, compounds recommended for mite control in soybean are limited to two organophosphates and one pyrethroid, bifenthrin.

Development of resistance in these two pests is not unexpected given the recent history of pesticide use in soybean and the demonstrated ability of pests within these taxa to develop resistance to insecticides. The propensity for this mite to develop resistance is well documented and it is difficult to manage in many systems because of the limited number of effective miticides. Resistance of soybean aphid to insecticides has not been documented in North America; although, there have been anecdotal reports of decreasing efficacy of pyrethroid insecticides in suppressing this species. 

The development of resistance is also a potential problem with a new invasive insect pest of soybean, the brown marmorated stink bug, Halyomorpha halys (hereinafter referred to as stink bug), that was first detected in Minnesota in 2010. This stink bug is causing greater than 50% yield loss in some soybean fields in eastern states. This insect rapidly repopulates sprayed areas and multiple applications are necessary for adequate control. Additionally, there is some evidence to suggest this species is developing resistance to pyrethroid insecticides.

Objectives

  1. Assess relative rates of resistance to insecticides of aphid, mite, and stink bug populations from throughout Minnesota. Regional populations will be sampled and bioassayed under controlled laboratory conditions for resistance to pyrethroid and organophosphate insecticides.
  2. Compare efficacy of available and potential insecticides/miticides against aphids and mites under diverse field conditions.
  3. Develop insectide/miticide recommendations that are both effective and economically sustainable.
  4. Disseminate regionally appropriate, IRM recommendations and information on pest susceptibility via print and electronic media and presentations.

Robert Koch in a soybean field.

Robert Koch explores pest management options for soybean production systems including the increasing insecticide resistance of several key pests. 

Spider mite.

photo credit: John Obermeyer

Resistance to the insecticide chlorpyrifos was confirmed in a two-spotted spider mite population from southwestern Minnesota in 2012.