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?