Weed Management Considerations for 2019: Kevin Bradley, University of Missouri - learning from our past in order to prepare for our future ...
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Weed Management Considerations for 2019:
learning from our past in order to prepare for our future
Kevin Bradley,
University of Missouri
Kevin Bradley, University of Missouri
#1. Never underestimate waterhemp/Palmer amaranth.
Shergill et al. 2018. Weed Science 66:386-394.
#2. It is going to take more than just herbicides.
Harvest Weed Seed Management:
The next major emphasis area in the fight against resistant weed species.
Investigating Windrow Burning in Missouri
Source: Dr. Stephen Powles. Professor, University of Western Australia
Temperature Levels in Narrow Windrow During Burn
800
Temperature at which
700 weed seeds have not been
documented to survive
600
500
TEMPERATURE (C)
400
300 ~13 minutes of
200 temperatures >500° C
100
0
0
60
900
120
180
240
300
360
420
480
540
600
660
720
780
840
960
1020
1080
1140
1200
1260
1320
1380
1440
1500
1560
1620
1680
1740
1800
1860
1920
1980
2040
TIME (SECONDS)
Influence of Cereal Rye Combinations
on Palmer Amaranth Emergence
50
No Cover Crop
Palmer Amaranth Density (#/m2)
Cereal Rye
40
Cereal Rye + Vetch
Cereal Rye + Crimson Clover
30 Cereal Rye + Winter Pea
20
10
0
Early Season Late Season
Webster et al. 2013. Crop Protection 52:130-135.
#3. The era of simple, flexible, convenient, and quick is over.
#4. Use full use rates and combinations of pre-
emergence residual herbicides (Group 14, 15) as
close to planting as possible.
Influence of Pre-emergence Herbicide Treatments on Waterhemp Density at the Time
of the Post-emergence Herbicide Application (results combined across 5 years)
20
POST Application (#/m2)
Waterhemp Density at
15
Most 2- or 3-way PRE herbicides
10 perform very similarly and are
very good on waterhemp
5
0#5. Overlapping residuals is a program that
fits the pattern of waterhemp/Palmer
amaranth emergence.
Residual, Pre-emergence Herbicide
Contact + Residual Herbicide#6. Glufosinate, 2,4-D, and dicamba are sites of
action that can still work, but if we abuse them
we will break them.
Only with a pre-emergence herbicide
Only with timely POST applications
© Dr. Kevin Bradley, University of MissouriWhat to do in a world with so many choices?
Influence of Soybean Traits on
Waterhemp Control (Renick, MO)
100 a a
a
a
90
80
Waterhemp Control (%)
70
60
50
40
30
20 b
10
0
Glyphosate Dicamba Glufosinate 2,4-D w/ 2,4-D w/
Glyphosate Glufosinate
Bars followed by the same letter are not significantly different, P> 0.05
© Dr. Kevin Bradley, University of MissouriShould Liberty & Roundup be Mixed?
University of Arkansas Study
Palmer amaranth control 14 days after treatment, averaged
over three sizes and four locations (1 to 24” tall)
•Liberty was a better option
than Roundup for Palmer
amaranth control
•The addition of Liberty to
Roundup increased Palmer
amaranth control over
Roundup alone
•No reduced control with
Liberty + Roundup tank-mix
Norsworthy 2018Should Liberty & Roundup be Mixed? • Liberty + Roundup applications should be made to small weeds to avoid antagonism of glyphosate on grasses • If environmental conditions do not allow for timely applications you can get in trouble • Optimize your application parameters (GPA, etc.) for Liberty • Can be a good tank-mix for glyphosate- resistant weeds like waterhemp & Palmer
All Things Dicamba: New Requirements, New Research Results, and Not-so-new recommendations.
Dicamba update for 2019
• Registrations expire 12/20/2020
• At the time of this presentation some online label
resources have not updated the dicamba labels.
• If looking at a label online, be sure to check the label
expiration date.New Requirements
• Only certified applicators (same as MO last year)
• Applications allowed on soybean up to 45 days after
planting or R1 (last year cutoff dates)
©Kevin Bradley, University of Missouri• Soybeans 2 Over The Top (OTT)
– Up to 45 days after planting or R1 growth stage
(beginning flower), whichever comes first.
• Cotton Producers
– Cotton OTT reduced from 4 to 2
– Up to 60 days after plantingSoybean Planting Progress - Missouri
100
Portion of expected acreage planted (%)
90
80
70
60
50
40
30
20
10
0
4/7
97 4/14
104 4/21
111 4/28 5/5 5/12
118 125 132 5/19
139 5/26 6/2 160
146 153 6/9 6/16
167 6/23 6/30 188
174 181 7/7 7/14
195 202
2018 2017 2016 2015 2014 2013
Source: USDA/NASSSoybean Planting Progress - Missouri
100
Portion of expected acreage planted (%)
90
80
70
60
50
40
30
20
10
0
Apr
10414 Apr111
21 Apr118
28 May
1254 May 11 May
132 13918 May
14625 Jun
1531 Jun 8
160 Jun 15 Jun
167 22 Jun
174 29
181
5-yr average
Source: USDA/NASSNew Requirements
• Only certified applicators (same as MO last year)
• Applications allowed on soybean up to 45 days after
planting or R1 (last year cutoff dates)
• Applications will be allowed from 1 hr after sunrise
to 2 hrs before sunset (last year 7:30 to 5:30)
©Kevin Bradley, University of MissouriWhen Did Inversions Begin Forming?
June 2018
20:30 Eastern
20:00 Eastern
19:40
19:00
18:00
18:00 17:55
19:05 19:05 18:50
18:00 18:55
18:55 17:35
17:25 16:15When Did Inversions Begin Forming?
July 2018
20:50 Eastern
21:25 Eastern
20:15
19:20
18:40
18:50 18:15
19:30 19:30
19:15
18:05
18:40 19:35 18:05
18:30 15:50Topography TN and IN: 2 stations; each set up
Real Time Monitoring for Inversion-
like Conditions
mesonet.missouri.edu
Funding for this project made possible by the Missouri Soybean Merchandising CouncilNew Requirements
• Only certified applicators (same as MO last year)
• Applications allowed on soybean up to 45 days after
planting or R1 (last year cutoff dates)
• Applications will be allowed from 1 hr after sunrise
to 2 hrs before sunset (last year 7:30 to 5:30)
• 110-ft downwind buffer + 57-ft buffer on other sides
in counties where endangered species may exist (new)
©Kevin Bradley, University of MissouriMissouri Counties Affected by Endangered Species
Restrictions as it Pertains to Applications of the
Approved Dicamba Products on Xtend Soybean
Har-
rison *In addition to the 110 ft
downwind buffer, an additional 57
ft endangered species buffer must
be maintained on all other sides of
the field in the highlighted
Pike
counties
Lincoln
Saint Charles
Johnson Pettis
Henry
Vernon
Cape
Girardeau
Barton
Dade
Jasper
Law-
rence
Mississippi
Dunklin
© Dr. Kevin Bradley, University of MissouriEndangered Species Protection Bulletin- EPA • Can access up to 6 months before pesticide application • Enforceable if referenced on pesticide label
New Requirements
• Only certified applicators (same as MO last year)
• Applications allowed on soybean up to 45 days after
planting or R1 (last year cutoff dates)
• Applications will be allowed from 1 hr after sunrise
to 2 hrs before sunset (last year 7:30 to 5:30)
• 110-ft downwind buffer + 57-ft buffer on other sides
in counties where endangered species may exist (new)
• Recommended to test spray solution pH and add a
buffering agent if < 5 (new)
©Kevin Bradley, University of MissouriNew Requirements
• Annual training requirement provided by registrants
or MU Extension (provided by us only last year)
We have online training
available (for a fee). At
this time, we do not intend
to offer in-person training
in Missouri. Contact your
local Bayer, BASF or
Corteva representative.
©Kevin Bradley, University of MissouriSome “New” Research Results
Analysis of Environmental Factors that may Influence Off-target Movement Based on all an analysis of ~200 on-target vs. off- target (but not physical drift) dicamba applications, the model suggests the following factors will increase the likelihood of off-target dicamba movement: • lower soil pHs • increase in max wind speed the day after application • increase in max dew point temp the day of application • nearby larger bodies of waters
Soil pH: Testing the Model
• Soil collected from Bradford
Research Center in fall 2017
• pH’s were adjusted to 4.3, 5.3, 6.9,
7.7, and 8.3 using hydrolyzed lime
or aluminum sulfate.
Non-dicamba • Two flats of soil were treated with a
tolerant soybean dicamba formulation and then
placed on the ground, between 2
soybean rows for 72 hours.
• Soybean were rated for dicamba
injury 14 days after treatment
(Oseland et al. preliminary results)Influence of Soil pH on Soybean Injury
as a Result of Dicamba Volatility
30
25 A
% Visual Soybean Injury
20
15 B
C
C C
10
5
0
4.3 5.5 6.8 7.7 8.3
*Bars followed by the same letter are not different Soil pH Levels
**Non-Treated was excluded from dataInfluence of Soil pH and Dicamba Formulation
on Soybean Injury
4.3 5.5 6.8 7.7 8.3
35
% Soybean Injury 14 Days After Trtmt
a
30 a
a
25
20 b b
bc bc bc bc
bcd cd
15
de e
10 ef ef
fg
fgh
5 hi hi
i
0
DGA DGA+VaporGrip BAPMA Choline
*Bars followed by the same letter are not different Dicamba FormulationResults from 2 Seasons of Dicamba Air Sampling (Volatility) Research Both Xtendimax and Engenia have been detected up to 96 hours after application in every experiment we have conducted Highest dicamba concentrations have consistently been detected during the nigh following an application made in either the evening or afternoon Dicamba ”peaks” have also been detected in the afternoon following evening applications
Not-so-new Recommendations • I believe these approved dicamba products can be used effectively and with less risk of off-target movement in the pre-plant burndown (April- May) for marestail, ragweeds, etc. • Until we learn something new or perhaps have a different product, I (still) believe the risk of off-target dicamba movement is too great (for the agricultural industry) to spray these products in June and July.
Why are some university weed scientists so concerned?
Symptoms of Dicamba on Pin Oak,
112 Days After Treatment
Non-Treated 0.025 lb dicamba
(1/20X rate)1/20,000th of the 1x Use Rate (0.000025 lb ae/A dicamba) – 14 days after application
Can LL, RR, and conventional tesoybean co-exist in a world with Xtend?
Email: bradleyke@missouri.edu weedscience.missouri.edu
App: ID Weeds (free download)
Facebook: Mizzou Weed Science
Twitter: @ShowMeWeeds
App: Herbicide InjuryIDYou can also read
