Weed Biology and Management Curtis Rainbolt Extension Weed Scientist Everglades REC.
Curtis Rainbolt Everglades REC University of Florida
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Transcript of Curtis Rainbolt Everglades REC University of Florida
Evaluation of hexazinone and diuron combinations for
preemergence weed control in Florida sugarcane
Curtis RainboltEverglades REC
University of Florida
Introduction• Limited number of PRE herbicides registered
for use in FL sugarcane• Atrazine• Ametryn• Flumioxazin• Metribuzin• Diuron • Pendimethalin
• Combination of hexazinone/diuron was recently labeled for FL sugarcane
PRE Challenges
• A majority of FL sugarcane is grown on muck soils
• Typically have 70-85% organic matter• Requires high use rates and residual control is
typically short• Very high weed pressures• Grower reluctance to make true PRE
applications
Introduction
• Atrazine at 3-4 lb/A + ametryn at 0.25 -1 lb/A is the most common treatment
• Typically applied POST to cane and early POST to weeds
• Typically results in light to moderate phytotoxicity
• Higher rates of ametryn can be used when cane is growing slowly
DuPont™ K-4™• 60 WG product• Commercial premix of 13.2 % hexazinone and
46.8 % diuron• In plant and ratoon cane, can be applied PRE
at 3.75 to 4 lbs/A• Can be applied POST to ratoon cane less than
18 inches tall• Post application when daily temperatures
exceed 80 F may result in crop injury
Objectives
• Determine optimum rates and ratios of hexazinone + diuron for PRE control of significant weed species
• Evaluate the effect of rate on crop injury
Materials and Methods
• 4 trials were established in spring 2005
• Plots were 4 rows by 50 ft long
• Sprayed with tractor sprayer at 20 GPA
• Weed control and crop injury evaluated visually
Herbicide treatments• K4 at 4lb/A• K4 at 6 lb/A• K4 at 8 lb/A• K4 at 10 lb/A• K4 at 4 lb/A + Sencor at 1 lb/A• K4 at 6 lb/A + Prowl H2O at 3.5 qt/A• K4 at 4lb/A + Direx at 2.5 lbs/A• and K4 at 6 lb/A + Direx at 2.5 lbs/A• Prowl H2O at 2.6 qt/A + Aatrex at 3 qt/A + Evik at 1 lb/A
(Studies 1 and 2)• Prowl H2O at 3.5 qt/A + Aatrex at 4 qt/A + Evik at 0.25 lb/A
(Studies 3 and 4)
Site 1• Applied March 15, 2005; Cultivar: CP80-1743
2nd ratoon• 10 DAT Crop injury was 5 to 6% with K4 at
10 lb/A, K4 at 4 lb/A + Direx, and K4 at 6 lb/A + Direx
• By 34 DAT, injury was no longer visible• Control of alligatorweed was 18 to 48% 22
DAT and 15 to 33% 34 DAT with K4 treatments
• Common purslane was controlled 89 to 95% 50 DAT
Alligatorweed 22 DAT with 8 lb/A K4
Weed Control• Control of fall panicum was 91 to 96% with all
treatments 22 and 34 DAT
Fall panicum control 50 DAT
0102030405060708090
100
K4 @4 lb K4 @6 lb K4 @8 lb K4 @10 lb K4 +Sencor
K4 + ProwlH2O
K4 @4 lb +Direx
K4 @6 lb +Direx
Prowl H20+ Aatrex +
Eviktreatment
% c
ontr
ol
ed e
b c d
d e
aa ba
b c
c d e
a
Untreated Control
K4 at 4 lbs/A + Direx
Site 2
• Applied March 21, 2005• Cultivar: CP89-2143 1st ratoon• Control of Alexandergrass ranged from 94 to
99% 18 DAT • All treatments controlled common
lambsquarters 95 to 100% 18 and 32 DAT
Alexandergrass control at Site 2Treatmenta Product 32 47
rate/AK4 4 lb 53 43
K4 6 lb 50 40K4 8 lb 78 55
K4 10 lb 63 63
K4 + Sencor 4 lb + 1 lb 78 73K4 + Prowl H2O 6 lb + 3.5 qt 80 80
K4 + Direx 4 lb + 2.5 lb 64 48
K4 + Direx 6 lb + 2.5 lb 65 55Prowl H20 + Aatrex + Evik 2.6 qt + 3 qt + 1 lb 91 88
LSD (0.05) 18 10aAll treatments included a non-ionic surfactant at 0.25% v/v
Alexandergrass ControlDAT
---------------------------------------%----------------------------------------
untreated control 47 DAT K4 4lbs/A 47 DAT
K4 10 lbs/A 47 DAT K4 6lbs + Prowl H2O 3.5 qt/A 47 DAT
Crop injury at Site 2
Treatmenta Product 18 32 47rate/A
K4 4 lb 9 9 9
K4 6 lb 11 5 6
K4 8 lb 10 8 8
K4 10 lb 16 9 13
K4 + Sencor 4 lb + 1 lb 14 8 10
K4 + Prowl H2O 6 lb + 3.5 qt 13 10 10
K4 + Direx 4 lb + 2.5 lb 14 13 11
K4 + Direx 6 lb + 2.5 lb 15 10 11
Prowl H20 + Aatrex + Evik 2.6 qt + 3 qt + 1 lb 5 0 0
LSD (0.05) 3 4 4aAll treatments included a non-ionic surfactant at 0.25% v/v
Sugarcane Injury
-----------------%-----------------
DAT
Stunting from K4 treatments
Sites 3 and 4
• Both applied on April 11, 2005• Both CP80-1743 first ratoon• Site 3 was cultivated and Site 4 was no till• Crop injury was similar at both sites, ranging
from 3 to 10% 14 DAT
Weed Control at Site 3
• 14 DAT fall panicum and alexandergrass control was 90 to 99% with all treatments
• Purple and yellow nutsedge were suppressed 23 to 30% 14 DAT
Weed Control at Site 3
Treatmenta Product 25 DAT 39 DAT 25 DAT 39 DATrate/A
K4 4 lb 65 30 63 35
K4 6 lb 80 30 64 30
K4 8 lb 75 53 71 48
K4 10 lb 88 50 80 43
K4 + Sencor 4 lb + 1 lb 80 68 70 53
K4 + Prowl H2O 6 lb + 3.5 qt 83 33 78 38
K4 + Direx 4 lb + 2.5 lb 86 65 70 45
K4 + Direx 6 lb + 2.5 lb 85 60 73 55
Prowl H20 + Aatrex + Evik 3.5 qt + 4 qt + 0.25 lb 85 45 78 63
LSD (0.05) 8 18 ns 24aAll treatments included a non-ionic surfactant at 0.25% v/v
Weed controlFall panicum Alexandergrass
-----------------%--------------------------------------------------------%----------------------------------------
Untreated control 39 DAT K4 at 10 lb/A 39 DAT
Weed Control Site 4• 14 DAT fall panicum and giant bristlegrass were
controlled 89 to 96% by all treatments• Giant bristlegrass control was 93% or higher with all
treatments 39 DAT Fall panicum control 39 DAT
0
10
20
30
40
50
60
70
80
K4 @4 lb K4 @6 lb K4 @8 lb K4 @10 lb K4 +Sencor
K4 +ProwlH2O
K4 @4 lb+ Direx
K4 @6 lb+ Direx
Prowl H20+ Aatrex +
Evik
treatment
% c
ontr
ol
NS at P = 0.05
Conclusions• Crop injury occurred at all sites, but was at
acceptable levels in CP80-1743• Crop injury was excessive in CP89-2143 and
tended to increase with higher rates and additional Direx
• Fall panicum and alexandergrass control initially was similar with all treatments, but higher rates typically had longer duration
Future Research
• Determine effect of growth stage and cultivar on phytotoxicity
• Develop use rates for sugarcane grown on sandy soils
Acknowledgements
• Thanks to DuPont for supporting these trials• Thanks to Glades Sugar Farm for providing
field sites
Any questions?