. . . . .  Additional County Reporting Today (July 22) . . . . . Lincoln County (Gary Nelson reporting) . . . . . Jerauld and Aurora counties (Thanks Russ Lutter) . . . . . Most Soybeans in SD Now at early R3 (beginning pod) . . . . . Union County (Thanks April Borders) . . . . . Hutchinson County (Thanks Roger Barrick) . . . . . Bon Homme County (Thanks Steve Sutera) . . . . Davison County (Thanks Blake) . . . . . Codington County (Thanks Buford) . . . . . Brown County (Thanks Tim Berndt and Gary "The Colonist" Erickson) . . . . . Minnehaha County (Craig Rosenberg Reporting) . . . . . Yankton County (Thanks to April Borders and Brad Ruden) . . . . . Soybean Aphids Detected at the SDSU Agronomy Farm in Brookings Wednesday June 22 on V3 Soybean (Thanks to Dr. Kelley Tilmon) . . . . .  Also in Brookings, Between 1 to 100 Soybean Aphids Per Plant Detected June 23 at the USDA ARS NGIRL (Thank You Dr. Louis Hesler) . . . . .  To the South, in Turner County on V4 Soybeans, Averaging 10 Aphids Per Plant (Thank You Brad Ruden and Connie Strunk)  . . . . .  SDSU Stage-Specific Economic Injury Levels Ready . . . . .

. . . . . Aphid Alert . . . . . Soybean Aphid Numbers Exploding With Dry Weather . . . . . Predominant Soybean Stage in SD is Now early R3 (Beginning Pod) . . . . . You Snooze, You Lose . . . . . Look For Newly-Born Nymphs on the Growing Points, Buford . . . . .

Last Updated on Friday July 22, 2005.

Nursery plants producing winged aphids 

Nursery soybean plants are plants (V3-R5) that have become overcrowded with soybean aphids
such that alates (fancy word for winged aphids) are now being produced by the colony to look for
resources (food and shelter) in uninfested or less infested soybean plants somewhere in the
soybean field.  These "winged ambassadors of ill-will" can also be carried by the wind to far away
soybean fields.

You heard it here first, the concept of nursery soybean plants on the field during the colonization
process of soybean fields by soybean aphids.  I have observed this same thing last season.

These nursery plants were initially infested by winged aphids coming from buckthorns.  Also, these
soybean plants are heavily defended by ants.  Natural enemies such as Asian lady beetles, minute
pirate bugs, syrphid flies, and nabid bugs have much less effect on the aphid population in these
plants, once again, because of the ants.

I am of the hypothesis that ants ("Go to the ant thou sluggard; Consider her ways and be wise") may
make it very hard for natural enemies to be useful in preventing economic loss due to aphids.


  Biocontrol enthusiasts must investigate both ants and nursery plants to ensure
   the utility of biocontrol agents as a practical tactic in integrated pest management.

Ant species that I have seen so far tending soybean aphids are Formica neogagates, Lasius
neoniger, Myrmica americana, and Formica obscuripes.  There are 77 species of ants in SD
and I do not know how many nest on soybean fields.

For all we know, ants, which are associated with different types of soil, may control the success or
failure of soybean aphids in colonizing fields.  That is, without ant, natural enemies may decimate
initial waves of aphid infestations, but, with ants present, depending on soil types on the field,
natural enemies become ineffective.

I wish I have the wherewithal to study ants again, and their distribution on the soybean field
depending on soil types.  I did this kind of work on open uncultivated rangelands from 1994-95
out there in Ludlow, SD and Amidon, ND.  It may be time to go to the ant again, eh Buford?

            Catangui, et al.  1996.  Abundance, diversity, and spatial distribution of ants (Hymenoptera: Formicidae) on
                               mixed-grass rangelands treated with diflubenzuron.  Environmental Entomology 25(4):  757-766. 

             Wheeler and Wheeler.  1963.  The ants of North Dakota.  University of North Dakota Press, Grand Forks.

             Wheeler and Wheeler.  1987.  A checklist of the ants of South Dakota.  Prairie Naturalist 19: 199-208.

Please click on the map below for more recent updates.  As of Friday July 22, 2005, a total
of 14 counties have reported soybean aphids.  On the average, the soybean plants in the state
at this time is early R3 (beginning pod stage).

On July 15, 2005, I stopped by a soybean field north of Crooks and saw many aphids.
I already notified Craig Rosenberg and gave him the coordinates of the field so that he can
then inform the grower.  Yes indeed, SDSU takes care of our soybean growers in the state.
As of yesterday (July 21), this field had already been sprayed with lambda-cyhalothrin.

A lot of the soybean aphids right now are newly-born nymphs on the growing points
of soybean plants.  Winged adults (from nursery plants on the field) are still flying all over
the place.  Scouting for the soybean aphids may be challenging at this time because
newborns are barely visible to the naked eye.  Time to whip out your trusty old magnifying
lens, or digital microscope.


Brand New! Stage specific economic injury levels for V5, R2, R4, and R5                  Ant Movie Clip

                                      

© Copyright 2010 by Mike Catangui. All Rights Reserved.
 

 Web Posted on Friday, July 1, 2005 by Mike Catangui.  Last Updated on Friday, July 22, 2005.