1. Curtis Rainbolt Everglades REC University of Florida
Evaluation of hexazinone and diuron combinations for preemergence weed control in Florida sugarcane
Curtis Rainbolt
Everglades REC
University of Florida

2. 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

3. 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

4. Introduction
Atrazine at 3-4 lb/A + ametryn at 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

5. 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

7. Objectives
Determine optimum rates and ratios of hexazinone + diuron for PRE control of significant weed species
Evaluate the effect of rate on crop injury

8. 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

9. Herbicide treatments K4 at 4lb/A K4 at 6 lb/A K4 at 8 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)

10. 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

11. Alligatorweed 22 DAT with 8 lb/A K4

12. Weed Control
Control of fall panicum was 91 to 96% with all treatments 22 and 34 DAT

13. K4 at 4 lbs/A + Direx
Untreated Control

15. 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

16. Alexandergrass control at Site 2

17. 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

18. Crop injury at Site 2

19. Stunting from K4 treatments

20. Sites 3 and 4 Both applied on April 11, 2005
Both CP 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

21. 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

22. Weed Control at Site 3

23. Untreated control 39 DAT
K4 at 10 lb/A 39 DAT

24. 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

25. Conclusions
Crop injury occurred at all sites, but was at acceptable levels in CP
Crop injury was excessive in CP 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

26. Future Research
Determine effect of growth stage and cultivar on phytotoxicity
Develop use rates for sugarcane grown on sandy soils

27. Acknowledgements Thanks to DuPont for supporting these trials
Thanks to Glades Sugar Farm for providing field sites

28. Any questions?