Spraying summer weeds safely and effectively
Summer weeds can rob crops of moisture and nutrients, and reduce crop emergence. Effective weed control will make sowing easier and lead to increases in crop yield and quality, but reckless pesticide use wastes money, can damage sensitive crops and poses health risks.
If you are spraying, there are some simple steps you can take to make sure you’re doing it right.
Preparing for summer spraying
Well before spraying, identify sensitive crops and areas (waterways, livestock paddocks or public spaces) near where you plan to use pesticide. Where possible, create a buffer zone, to protect areas at risk of spray drift.
Pesticide is more effective when weeds are healthy and actively growing, rather than under stress. Research has shown spraying ten days after significant rain is ideal. You don’t want to be scrambling to prepare in the wake of wet weather. Check your sprayer’s performance well before you use it. The Grains Research and Development Council (GRDC) has a helpful factsheet with pre-season sprayer checks and calibration tips.
Tips for safe spraying
- Make sure the person spraying has the necessary and up-to-date certifications for using pesticides.
- Make sure the Safety Data Sheet that comes with the pesticides is read and understood as well as any specific emergency procedures required for that chemical.
- Follow all the relevant workplace health and safety guidelines, such as wearing PPE, when handling chemicals.
- Follow instructions on the agricultural chemical product label accurately. Pesticides may have specific spray drift management instructions.
- Use applicators and nozzles to minimise drift and maximise efficiency, and maintain the correct boom height for the nozzles you use. Coarser droplets are less likely to drift.
- Only spray when the prevailing weather conditions are suitable, to avoid drift and ensure the efficacy of the pesticide.
- Follow instructions on the storage and disposal of agricultural chemicals
Weather conditions and spraying
- Winds should be steady, between 3-15km/h and blowing away from susceptible crops.
- Avoid spraying in temperatures near or above 30°C and when humidity is low, as it reduces droplet size, increasing the risk of spray drift.
- Do not spray when there is surface temperature inversion. Visual indicators include fog, dew or frost, and smoke or dust hanging in the air.
- Delta T, calculated by subtracting the wet-bulb temperature from the dry-bulb temperature, should be between 2 and 8, and no greater than 10.
The importance of spray records
It is a legal obligation to keep detailed records of each spray application. If there are issues with pesticide use in your area, having accurate records will help prove you have sprayed responsibly.
Other benefits of accurate spray records include:
- You can analyse the effectiveness of treatments.
- It’s helpful when you design integrated pest management programs.
- You can calculate paddock cost of production for better financial insights.
- You can track paddock withholding periods.