Colorado Wheat Entomology Newsletter

Darren Cockrell: Darren.Cockrell@colostate.edu, 630-649-4419

Dr. Punya Nachappa: Punya.Nachappa@colostate.edu, 785-383-4873

Introduction

Hello, this year we are starting a new Wheat Entomology Newsletter, led by Darren Cockrell, Research Associate and myself, Dr. Punya Nachappa, entomologist and Assistant Professor in the Department of Agricultural Biology (www.nachappalab.com). With the retirement of Dr. Frank Peairs, I am leading the wheat entomology research until we hire a replacement. In this newsletter, we will bring you updates about insect/mite issues and management tips.  If you suscept you have insects/mites, please don’t hesitate to reach out to us. I am also on Twitter @NachappaPunya

Russian Wheat Aphid

Wheat fields in the SE portion of the state (particularly near Walsh, CO) have been reported to have high numbers of Russian wheat aphids. The dry winter and spring will likely increase the infestations this year. Scout your fields regularly for the white or purple chlorotic streaking that the aphids cause (Figure 1).  We are testing the aphids to determine if it is a new biotype.

Figure 1: Russian wheat aphid damage in Walsh, CO. Photo from Kevin Larson.

 Wheat curl mites

USDA wheat plots with the variety Guardian in Lane County, KS are reporting very high population of wheat curl mites. We obtained leaf tissues and confirmed the presence of mites. Some reports in western Kansas that Byrd and Avery are showing high wheat streak mosaic symptoms suggesting that mites are adapting to the resistance gene. There are no effective miticides for wheat curl mites so growers cannot be lax with volunteer wheat control, which is the most effective management practice for the and the viruses it vectors.

According to an expert from Montana, when you first see yellowing of plants in spring, do not apply nitrogen because it will result in increased mite reproduction and spread of the virus. If you suspect you have mites, please send your samples to our laboratory for testing prior to applying nitrogen.

 Wheat Stem Sawfly Statewide Survey

The statewide survey of wheat stem sawfly in wheat fields will continue for the 10th consecutive year. Hot spots in 2020 were found in Weld, Morgan, Logan, Sedgwick, Washington, and Adams counties, however the severity of infestations in the southern counties has also continued to rise. We will inform you about the on-going survey in this newsletter.

 Wheat Stem Sawfly and Insecticide Control

Multi-year efficacy trials at CSU to control sawfly by using the common insecticides: Warrior II, Endigo ZCX, Lorsban Advanced, Cobalt Advanced, and the growth regulator Palisade, have all been found to be largely ineffective. Research conducted on Thimet 20G in Colorado has shown it to be intermediately effective, but being extremely susceptible to being washed out by rain before controlling the larvae.

Current research in controlling sawfly with insecticides is centered on foliar treatments of Endigo ZCX with penetrating products to aid in uptake. Some reduction in larval infestation has been found using precise application timings, however the results are preliminary. No insecticides are currently approved for controlling wheat stem sawfly.

Brown Wheat Mites

There are reports of brown wheat mite infestations near Walsh, CO. The hot and dry conditions may have led to above average populations. The economic threshold for this pest is not well defined, but during an outbreak spraying with insecticide is the only option.

 

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