Soybean aphid infestations and reports of failures of pyrethroid insecticides to control soybean aphid

Robert Koch (Extension Entomologist), Ian MacRae (Extension Entomologist), Bruce Potter (Extension IPM Specialist), and Phil Glogoza (Extension Educator – Crops)

By now you should be scouting your soybean fields for soybean aphid on a regular basis.  Soybean aphid can be found in most fields throughout the state and populations have reached economic threshold (250 aphids per plant) in some fields in northwest Minnesota and have require insecticide application to protect soybean yield.  In northwest Minnesota (especially around Norman County), applications of pyrethroid insecticides are failing to adequately control aphid populations in some, but not all, fields.  

The Dicamba Dilemma: Facts and speculations

Used with permission by Aaron Hager, University of Illinois

Dicamba injury to soybeans in a southwestern Minnesota field. Photo: Stephan Melson

Dicamba injury to non-target crops has dominated Extension discussions this week. Non-tolerant soybeans are extremely sensitive to this chemical and damage has been reported in a number of fields throughout the state. The following article by Dr. Aaron Hager at the University of Illinois echoes observations we have been making in Minnesota and summarizes injury symptoms on soybean, possible routes of exposure, and potential yield effects. His article is reprinted in its entirety:

Herbicide Mode of Action and Crop Injury Symptoms at the University of Minnesota Field School for Ag Professionals

by Dave Nicolai, IAP Program Coordinator

This year at the Field School, participants will have two opportunities to learn, re-learn or fine-tune their skills in linking visual symptomology to the common herbicide modes of action commonly used in corn and soybean and gain in-depth knowledge of growth regulator herbicide movement and symptomology in soybean.

Weed management has changed dramatically in recent years. The large number of herbicide options—new products, old products with new names, new formulations of old products, premixes, and generics—can make weed control appear to be a difficult and confusing task. Knowing and understanding each herbicide’s mode of action is an important step in simplifying and selecting the proper herbicide for each crop, diagnosing herbicide injury, and designing a successful and durable weed management program for a farmer’s production system.

Lunch and Learn Webinar: Managing Ash Content in Hay

Krishona Martinson - University of Minnesota

On Wednesday, August 23, 2017 from 12:00 to 1:00 pm (central time), the University of Minnesota will host a free webinar titled “Managing Ash Content in Hay”. Dr. Marvin Hall, Professor of Forage Management from Penn State University, and Abby Neu, Extension Educator from the University of Minnesota Extension, will present the webinar.

Hay Rake Impacts Ash Content in Alfalfa Hay

Abby Neu, Craig Sheaffer, Scotty Wells and Krishona Martinson, University of Minnesota; Marvin Hall and Dan Kniffen, Pennsylvania State University; and Dan Undersander, University of Wisconsin.

Summary: Using a hay merger or sidebar rake to combine swaths resulted in less ash content compared to a wheel rake; however, rake-type rarely resulted in differences in forage nutritive value. In addition to wide swaths, cutting heights ≥2 inches, and flat mower knives, the use of a hay merger or sidebar rake can be added to the list of best management practices to reduce ash content in alfalfa hay.

Pre-harvest Management of Small Grains

To save time and money most of you prefer to straight cut your wheat, barley, rye or oats.  The allow for straight cutting the crop has be evenly ripe across the field and the straw and grain has to be dry enough that it will feed through the combine.

Waiting for a whole field to dry down poses a risk for the portion of the field that is already harvest ripe, including sprout damage, straw breakage and lodging. To even out dry-down and/or speed up dry-down you have two basic options. Swathing or windrowing, at one time, was the default operation that signaled the beginning of harvest.  A second preharvest option is an application of glyphosate at the hard dough stage.

Glyphosate is labeled as a harvest aid to control late emerged weeds that may interfere with harvest. The RoundUp PowerMax II  label doesn't define it as a desiccant. Research has shown that glyphosate applied with or without ammonium sulfate may hasten drydown of the wheat crop if conditions for drydown are adverse. With a preharvest interval of 7 days, a couple of days, at the most, may be gained. Previous Minnesota Crop News post provide details about swathing and preharvest glyphosate.

White Heads

Jochum Wiersma, Ian MacRae, and Madeleine Smith

Is not the reincarnation of the Detroit rock due the White Stripes but a phenomenon that often can be seen this time of year in wheat fields are they are starting to ripen.  The causes of these premature ripened heads are varied and a diagnostic key can be found here.

People of commented that especially the wheat stem maggot is more prevalent this year and my travels to the different field trials across the state confirm this. The seemingly high numbers of wheat stem maggot may be related to the mild winter conditions.  Several insect pests that overwinter in Minnesota have had comparatively high and early populations this year.

Incidence will generally be worse along field edges and taper off as you walk further into the field.