Herbicide Drift, Sensitive Neighbours and Equipment Hygiene
A horticulture business maintains a 2 ha production nursery adjacent to a market garden growing leafy greens and a small vineyard. A worker plans to spot-spray glyphosate for weeds along a shared fence line and to apply a selective broadleaf herbicide on a lawn area near the nursery entrance. Wind is forecast at 12 km/h gusting to 20 km/h from the west; the market garden is west of the fence and the vineyard is east. The spray unit was last used with a residual herbicide three weeks ago and was rinsed once with water. Tomatoes in a nearby greenhouse show cupped, twisted new growth, though no spray has been applied there yet.
1. Assess the risks and decide whether to proceed, and under what conditions.
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Do not proceed as planned. Wind from the west at 12–20 km/h will carry spray toward the market garden, and the broadleaf herbicide near the entrance poses a drift risk to any sensitive crops downwind. Glyphosate along the fence also risks drift onto the market garden. The single water rinse after a residual herbicide is inadequate; residual herbicides can persist in tanks and hoses and cause exactly the kind of cupped, twisted growth seen in the greenhouse tomatoes, which suggests prior contamination or off-target movement. Before any spraying: check the label and local restrictions, confirm wind speed and direction at the site, and choose a low-drift nozzle and pressure. Consider wick wiping or hand removal along the fence instead of spraying. For the lawn, use a product and method appropriate to the site, or postpone until conditions are suitable. Investigate the tomato symptoms as a possible contamination incident before resuming.
2. Outline the equipment hygiene and record-keeping steps required before the spray unit is used again.
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Triple-rinse the tank, lines and nozzles with clean water, using a tank-cleaning agent if the label specifies one, and run the rinse through the pump and boom. Rinse the exterior and flush the hoses. Dedicate separate tanks or nozzles for residual herbicides if possible. Record every step: product, rate, date, tank rinse history, operator and weather. Before use, do a small test on a sensitive indicator plant if there is any doubt. Maintain a spray diary including wind speed and direction, temperature, target and buffer zones. Notify neighbours in advance where required by local rules, and keep buffer distances from the fence and vineyard. Review the incident with the greenhouse tomatoes, document findings, and adjust procedures so a rinse-once practice is never repeated.