. . . . . Have a Safe and Bountiful Harvest! . . . . .

Clear difference between sprayed and unsprayed soybeans

I was in our soybean aphid research plots today to see how the plants and insects were doing.

There appears to be a clear difference between soybeans that were sprayed once on July 28
(20 gallons of finished mixture per acre) and the unsprayed plots.  I took many photos for our
winter meetings.  Not going to reveal to you yet exactly what treatments I have this year.

The unsprayed soybeans were about a foot shorter, the canopy not fully closed, and starting
to senesce compared with sprayed soybeans, in general:


                                                                               


You are welcome to visit my plots in the next 2 weeks if you wish.  Let me know and I could show
you either our Brookings or Beresfod plots.  Our soybeans are currently in the R5.5 stage.


Buggy Q of the Week: Do we kill more natural enemies when we spray early or late?
 
[Above update was posted by Mike Catangui on Wednesday August 27, 2009.]

Aphid doubling time may only be a day


Actual reports from the field indicate that the aphid doubling time may only be a day.  The formula
for calculating doubling time can be found at Wikipedia (http://en.wikipedia.org/wiki/Generation_time).

                                            

A famous scientist reported on a conference call that he saw aphids increase from 30% of plants
infested with about 20 aphids per plant (about 6 aphids per plant) to 100% of plants with about 500
aphids per plant in 7 days (from July 18 to July 25, 2008).

If my calculations were correct, using the above formula, the doubling time is only a single day using
the above open-field, un-caged, with-all-the-glorious-natural-enemies, rain-shine-hail scenario.

What - a - diff'rence - a - day - make? . . . 24 little hours . . . . Here today, double tomorrow . . . That
reminds me, Buford, what will 250 be in 48 little hours?  Forty - eight - little - hours . . .

[Above update was posted by Mike Catangui on Friday, August 15, 2008.]

Soybean aphid numbers very high in areas     

Reports from coops around the state indicate that the soybean aphid is in high numbers in most
soybean growing areas.  This afternoon, I heard from area agronomists that almost all of the
soybean acres in Yankton and Clay counties have been or will be sprayed for soybean aphids.
That will be an estimated total of 161,000 acres between the two counties.

Heavy spraying also is being reported in Minnehaha, Turner, and Lincoln counties; there has been
a logjam or delay in timely spraying because of muddy fields in some areas.  I will have an estimate
of sprayed acres later.

An airplane crop sprayer from Vermillion reported very high numbers of winged aphids up in the air.

I have never seen this high number of soybean aphids this early here in our Brookings and Beresford
research plots; I sprayed our plots (at R2 stage) on July 28, 2008.  We sprayed our Beresford plots
from August 6-8.

Make sure to use the correct research-based economic thresholds (Commentary) especially if spraying
will be delayed by more than three days - use our Soybean Aphid Stage-Specific EIL.

You can also find a new list of soybean aphid insecticides from my Web site at:

http://plantsci.sdstate.edu/ent/entpubs/sa_insecticides.htm                             

Call or e-mail me for any questions.


New! Continuing Education: Impact of Aphids on Soybean Yield Components
 

Bean leaf beetles increasing up north   

I also spoke with a crop consultant in Brown County tonight; he indicated that bean leaf beetles
are showing up in R2 (full bloom) soybean right now in the area.

He reported an average of 8 beetles per sweep in southern Brown County and 3-4 per sweep
around Aberdeen.  According to him, with the current market value of soybean, almost all soybean
acres in Brown County will be sprayed.  Over 200,000 acres of soybean is grown in Brown County.

The economic threshold is 2 bean leaf beetles per sweep (at $12 per bushel soybean, $10 per acre
control cost, and 45 bushel per acre yield potential.

Find information on managing the bean leaf beetle in my Web site:

http://plantsci.sdstate.edu/ent/entpubs/blb_mgmt_sd.htm

New! Bean Leaf Beetle Insecticides for 2008

© Copyright 2008 by South Dakota State University.  All Rights Reserved.

 Web Posted on Friday, August 1, 2008 by Mike Catangui. Last Updated on Monday, September 8, 2008.