Browsing by Author "Davis, AM"

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Combining weed efficacy, economics and environmental considerations for improved herbicide management in the Great Barrier Reef catchment area
(Science of the Total Environment, 2020) Fillols, E; Davis, AM; Lewis, SE; Ward, A
The current Australian sugarcane industry transition toward adoption of an ‘alternative’ herbicide strategy as part of improved environmental stewardship is increasingly complicated by recent farming system, regulatory and herbicidal product changes. This study quantified and compared the efficacy, economic costs and environmental risk profiles of a range of established, emerging, and recently registered pre-emergent herbicides across field trials in the Wet Tropics region of North Queensland. Several herbicides were effective on certain weed species, but lacked broad spectrum control. Better efficacy results from products with multiple active ingredients (i.e., imazapichexazinone) demonstrated the benefits of using mixtures of active ingredients to widen the spectrum of weed control efficacy. All tested pre-emergent herbicides behaved quite similarly in terms of their propensity for off-site movement in water (surface runoff losses generally N10% of active applied), with their losses largely driven by their application rate. Herbicides with lower application rates consistently contributed less to the total herbicide loads measured in surface runoff. Results demonstrated alternative choices from the more environmentally problematic herbicides (such as diuron) are available with effective alternative formulations providing between 4 and 29 times less risk than the traditional diuron-hexazinone ‘full rate’. However, considerable challenges still face canegrowers in making cost-effective decisions on sustainable herbicide selection. Additional research and effective grower extension are required to address information gaps in issues such as specific weed control efficacy of alternative herbicides and potential blending of some herbicides for more effective broad spectrum weed control, while also minimising environmental risks.
Efficacy and environmental runoff impact of alternative pre-emergent herbicides to diuron applied on trash blanketed ratoons
(ASSCT, 2018) Fillols, E; Davis, AM; Lewis, S
The efficacy of alternative pre-emergent herbicides to diuron applied just after harvest on green trash blanketed ratoons was investigated in three field trials in the wet tropics, Far North Queensland. The study also compared the losses of the tested pre-emergent herbicides in runoff using rainfall simulations. The commercially available pre-emergent herbicide Bobcat®i-MAXX (imazapic + hexazinone), was as efficient as Barrage (diuron + hexazinone), while other tested active ingredients like imazapic, isoxaflutole and amicarbazone were effective only on some weed species. All tested herbicides were found in runoff water at levels aligned with their application rate. Herbicides applied at lower application rates such as imazapic and isoxaflutole had minimal environmental runoff footprints when compared with diuron. All tested alternatives were proven more environmentally friendly than diuron.
Impact of application depth and slot closure on runoff losses of imidacloprid
(ASSCT, 2020) Fillols, E; Davis, AM
Imidacloprid represents the Australian sugar industry’s best canegrub-management tool, but it has been detected in many water bodies, including groundwater, creeks, rivers and marine environments, posing a potential risk to the health of the Great Barrier Reef. In ratoon cane, it is commonly applied in liquid form with coulters within the cane row. Imidacloprid product labels state that, when applied in ratoons, the product must be placed at 100–125 mm depth and the slot must be covered; however, it is not uncommon to observe application equipment that does not maintain the desired depth or fails to close the slot appropriately. To investigate the best application methods to reduce imidacloprid runoff, two rainfall-simulation trials were established in the Burdekin and in the Wet Tropics to assess the impact of depth and slot coverage on imidacloprid runoff when the liquid formulation is applied with a stool-splitter tine implement. An additional runoff trial under overhead irrigation was set up in the Wet Tropics to test the efficacy of the StoolZippa™ to close the slot and reduce imidacloprid runoff losses when the product is applied at the correct depth of 100 mm. Results from the rainfall-simulation trials showed higher imidacloprid concentration in runoff from a shallow application at 50 mm compared to the recommended minimum 100 mm application depth. A press wheel reduced the imidacloprid concentration to nil when the product was applied at the correct depth of 100 mm; however, it slightly increased the concentration in the case of the shallow application. In the overhead-irrigation trial, the StoolZippa™ increased the imidacloprid concentrations in runoff versus the slot left open, but these concentrations were still extremely low and not of environmental concern. These trials indicate that ensuring the product is consistently applied at 100 mm depth is the best way to reduce imidacloprid loss via runoff when the product is applied with a stool-splitter tine implement. As trials were only conducted in loam soils at two locations, further trials are recommended over a range of soil types and geographic locations.