duration of yellow nutsedge competitiveness after treatment with various herbicides
DESCRIPTION
Duration of yellow nutsedge competitiveness after treatment with various herbicides. J. A. Ferrell*, H. J. Earl, W. K. Vencill University of Georgia. CYPER Competition. C4 perennial that reproduces vegetatively Higher photosynthetic rate than most crop species. - PowerPoint PPT PresentationTRANSCRIPT
Duration of yellow nutsedge competitiveness after treatment
with various herbicides
J. A. Ferrell*, H. J. Earl, W. K. Vencill
University of Georgia
CYPER Competition
• C4 perennial that reproduces vegetatively• Higher photosynthetic rate than most crop
species.
• Yield reductions between 59 and 87% for corn, rice, and soybeans.
• Alternate host for pathogens.
Objectives
• Determine time required for glyphosate, bentazon, imazapic and halosulfuron to render SORHA
physiologically noncompetitive
Physiologically non-competitive
• 50% reduction in net carbon assimilation (AN)
Biomass accumulation most common parameter to describe competitiveness
Biomass accumulation directly linked with AN
50% reduction in AN was a comparative indicator of competitiveness
Materials and Methods
• CYPER grown in greenhouse for 20 wk
• Herbicide Treatments Glyphosate 840 g ai ha-1
Halosulfuron 140 g ai ha-1 + NIS Imazapic 70 g ai ha-1+ NIS MSMA 2200 g ai ha-1+ NIS Bentazon 840 g ai ha-1+ COC
• Plants treated at ~25 cm
CYPER plants before treatment
Materials and Methods
• Photosynthesis and Stomatal Cond. Li-Cor 6400
PPFD = 1200 µmol m-2 s-1 CO2 concentration (sample side)
= 360 µmol mol-1
Materials and Methods
• Experiment conducted twice
• Randomized Complete Block Design with 5 replications
• All data normalized to the control
• The data were pooled across runs
Effect of Herbicide on AN
020406080
100120140
0 2 4 6 8 10 12
days
AN (
% o
f c
on
tro
l)
glyphosate
imazapic
halosulfuron
Error bars = LSD(0.05)
Effect of Herbicide on AN
-10
10
30
50
70
90
110
130
0 2 4 6 8 10 12
days
AN (
% o
f c
on
tro
l)
MSMA
bentazon
Error bars = LSD(0.05)
AN50 Values
Herbicide
Rate
(g ai ha-1)
AN50
(days)
Glyphosate 840 3.2 b
Halosulfuron 70 1.6 a
Imazapic 70 2.1 a
MSMA 2200 3.3 b
Bentazon 840 --
Regrowth Biomass
Herbicide
Rate
(g ai ha-1)
AN50
(days)
Regrowth
(g)
Glyphosate 840 3.2 b 2 a
Halosulfuron 70 1.6 a 0 a
Imazapic 70 2.1 a 0 a
MSMA 2200 3.3 b 5 a
Bentazon 840 -- 44 b
Bentazon recovery
• Label suggests bentazon should be applied sequentially (7-10d) for CYPER control.
• Pattern of AN decline and recovery 5 DAT has been observed in rice. Recovery was attributed to metabolism 85% metabolism observed 4 DAT
Effect of Herbicide on gs
020406080
100120140
0 2 4 6 8 10 12
days
gs
(% o
f c
on
tro
l)
MSMA
glyphosate
halosulfuron
imazapic
Error bars = LSD(0.05)
MSMA and gs
• MSMA possibly inhibits the malic enzyme in C4 plants (Knowles and Benson 1983).
• Accumulation of malic acid may lead to photooxidative damage (Devine et al. 1993).
Hypothesis• Cellular leakage, leading to guard cell
dysfunction, resulted in unregulated water losses via stomata.
• Compromised cuticular integrity caused water loss from epidermal cells.
Conclusions
• Halosulfuron and imazapic renders CYPES physiologically non-competitive more quickly than glyphosate, MSMA, or bentazon.
• A single application of bentazon did not control CYPES
• gs highly correlated with AN, except for MSMA
Any Questions?