No Observable Effect Levels were determined for four commonly used forestry herbicides on glasshouse grown tomatoes. For metsulfuron and glyphosate, NOELs based on visual symptoms were lower than those for dry weight production (ED5). For triclopyr the values were similar. The rates used for clopyralid/picloram mixtures allowed for a visual NOEL to be determined but were too high for the determination based on dry weight. The value of the NOEL varies with the method used to determine it.
Spray Safe Manager (SSM) is a computer-based aerial application model, which unlike previous models, has a simple user interface. SSM not only predicts spray deposition but also integrates this data with herbicide-plant dose-response curves. This latter facility allows the operator to predict the size of buffer zone required to avoid damage to sensitive plants outside the spray area and the degree of weed control within the spray block. Validation trials showed that, for a helicopter applied spray, the model tended to overpredict spray deposition on stainless steel plates close to the spray block and underpredict deposition in the region 32-80 m from the centre of the spray release line and on isolated plants. The accuracy of model prediction was greater when the spray was applied using D8-45 nozzles orientated at 90°, than for spray applied using D6 nozzles orientated at 0°. The reasons for this are discussed. The model can also be used to predict possible work rates, hectares sprayed per hour, and potentially as a training tool.
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