Transcript Roundup tank partners - Iowa State Weed Science Online

Weed Shifts in RR Crops
 Two
types of shifts
– Tolerant species
» Nutsedge, waterhemp, velvetleaf
– Resistant biotypes
 Rate
that shifts occur will be
dependent on how the technology is
used
Shifts to tolerant weeds
 Several
common weed species can
survive label rates of Roundup
 These
species will increase in prevalence
with continued use of Roundup Ready
crops
Effect of Plant Tolerance on
Roundup Ultra Consistency
% of applications that provide acceptable control1
100
80
60
40
20
0
Foxtail
Sunflower
Tolerance
1Hypothetical
data. Hartzler. ISU.
Cocklebur
Waterhemp
Y. nutsedge
Effect of Plant Tolerance on Roundup
Ultra Consistency
% of applications that provide acceptable control1
100
80
60
40
20
0
Foxtail
Sunflower
Tolerance
1Hypothetical
data. Hartzler. ISU.
Cocklebur
Waterhemp
Y. nutsedge
Time of application
 Does
time of day effect control?
– Many cases in 1998 of reduced efficacy
with treatments after dusk
– No clear explanation of why
– May not be a consistent effect
 Does
dew have an effect?
– Light dew should not
– When to the point of “run-off” there may
be reduced efficacy
Temperature effects
 Herbicides
perform best when weeds
are actively growing
 Lower
temperatures = slower plant
processes = slower herbicide action
 Limited
ability to predict when
performance will begin to be affected
Waterhemp in RR Crops
 Two
mechanisms for escape
– Relatively high tolerance
– Late emergence
 Both
characteristics influenced
strongly by environment
– Problems will vary from year to year
Waterhemp Tolerance to Roundup
 Numerous
cases of control failures
– Everly, IA situation
» 3 applications - total of 108 oz/A (28, 32,
48)
» Everly biotype no more tolerant than
biotype from different field in greenhouse
 Factors
influencing tolerance
– Temperature, moisture, weed size, time
of day, spray coverage, etc.
Late emerging weeds
 Late
emergence allows weeds to
escape Roundup applications
 Initial emergence of waterhemp 1-3
weeks later than giant foxtail
 Late emergence places weeds at
competitive disadvantage
Waterhemp time of emergence study
 Four
Roundup application timings
– At planting, 2, 4 or 6 trifoliate stage
 Waterhemp
plants emerging within
one week of applic. flagged
 Waterhemp survival, growth and
seed production determined
 Soybean yields within 1 m radius
 Sponsored by ISPB
Influence of emergence date on
waterhemp survival and growth
120
3 lb
100
80
AP
2 Tri
4 Tri
6 Tri
60
40
20
0
Survival (%)
Hartzler and Battles. 1998. ISU.
Height (in)
Wt (% of AP)
Relationship between waterhemp
and soybean yields
4000
3500
3000
2500
2000
1500
1000
500
0
0
10
20
30
40
50
Soybean yield (bu/A)
60
70
80
Waterhemp time of emergence study
 Similar
studies conducted in 1997
 Waterhemp emerging after 2nd
trifoliate failed to survive
 May-June rainfall
– 1997
– 1998
7.1”
17.3”
Potential for resistance to Roundup
 Evidence
supports view that risk for
resistance is very low
– History of use without resistance
– Difficulty in developing RR crops
 However,
several examples of
selection of resistant biotypes
Resistance to Roundup
 Controlled
selection studies
– Perennial ryegrass - 5X increase in tolerance
– Birdsfoot trefoil - 3X increase in tolerance
 Rigid
ryegrass - Australia
– Resistance confirmed at two locations
– 7 to 11X resistance
Roundup tank partners
 Many
products promoted as partners
with Roundup
 If you can’t beat ‘em, join ‘em
 Strategy
– Better control of ‘tolerant’ species
– Provide residual for one pass program
Roundup tank partners for
residual control
 May
lengthen control period from a
single application
 Concerns
– applying during peak weed emergence
– rain is critical for optimum residual
effectiveness
– interception by foliage interferes with
distribution on soil surface
Development of weed
management programs
 Goals
of weed management
– full-season weed control
– protect yield potential
– economically feasible
 No
single tactic, regardless of
product(s), will consistently achieve
these goals
120
60
100
50
80
40
60
30
40
20
20
10
0
0
Roundup Roundup Roundup Roundup
PRE +
PRE +
PRE + Untreated
early
mid
late
early + late Roundup Roundup Roundup
check
early
mid
late
Foxtail control (%)
Waterhemp control (%)
Pringnitz and Hartzler, Kanawha, 1998.
Yield (bu/a)
Soybean yield (bu/a)
% control
Effect of application timing on
soybean yield and weed control
New Products for 1999
 Aim
- FMC
– Postemergence broadleaf control in corn
– Same family as Authority
– PPO inhibitor
– Fairly narrow spectrum of control
»Velvetleaf, lambsquarter, redroot pigweed,
morningglory, nightshade
Product Update
 Authority
– Now marketed solely by DuPont
» Authority 75% DG 4 - 5.3 oz/A
» Canopy XL 3.6 - 8.8 oz/A
– Injury problems in Missouri
» Associated with poorly drained soils
» Tank-mixes with Prowl caused greatest
problems
Product Update
 Axiom
- Bayer
– New amide herbicide + metribuzin
»54.4% FOE 5043 + 13.8% metribuzin
– 16 oz Axiom = 0.17 lb metribuzin
– Preemergence grass control
» corn: 13 to 23 oz/A
»soybean: 7 to 13 oz/A
New Products for 1999
 Balance
- Rhone Poulenc
– Preemergence broadleaf and woolly
cupgrass in corn
– Registered in 16 corn-belt states
»No label in MN or WI
– EPA concerns
»Groundwater and surface water
»Off-target injury
New Products for 1999
 Balance
– Good to excellent on most broadleaves
»Weaknesses - cocklebur, wild buckwheat
– Better on woolly cupgrass than amides
– Fair on foxtail
– Package mix with ai in Axiom is planned tradename of Epic
New Products for 1999
 Balance
– Bleaching herbicide
»Carotenoid inhibitor
»Different site of action than Command
– Crop injury potential
»Corn injury has been observed
»Normally short-term response
‘New’ Products for 1999
 DuPont
- BASF Marketing Project
– Celebrity
»0.5 pt Banvel + 0.67 oz Accent
– LeadOff
»2.33 lb Frontier + 2.67 lb atrazine/gal
»Same actives and ratio as Guardsman
‘New’ Products for 1999
 NorthStar
- Norvartis
– Post broadleaf control in corn
– Replacement for Exceed in Iowa
– Equivalent to:
0.5 oz Beacon + 0.23 pt Banvel
– 5 oz/A on 4 to 36” corn
New Products for 1999
 Distinct
- BASF
 Registration pending - February 1999?
 Premix of dicamba + diflufenzopyr
 New mode of action - antiauxin
 Good broadleaf control, provides some
suppression of grasses
 6 oz on 4 - 10” corn; 4 oz on10 - 24” corn
 6 oz = 0.188 lb ai dicamba per acre
Drift Retardants
 Several
products now available
 Reduce formation of small droplets
 Growth in RR has driven use
 Reduce drift potential, DO NOT
eliminate drift