Spraying with results:
June 21, 2005
7 tips for best fungicide coverage
Thorough spray coverage is one of the keys to good weed and disease control, says Vern Hofman, NDSU extension agricultural engineer.
He offers the following tips on improving coverage, based on a recent report from Ohio State University.
1. Use low-drift nozzles, such as flat-fan pattern, and spray pressures (60-70 psi) that will produce 200-300 micron droplets in a controlled pattern.
2. Adjust boom height for the nozzle fan angle. The spray should overlap 50%. If the boom is too high, the spray has farther to travel before it reaches the crop canopy and is subject to drift.
3. Use air-assisted sprayer when possible. In OSU tests, these produced the best coverage.
4. If air assist sprayer isn't an option, use fine to medium flat fan spray nozzle in a directed, or drop nozzle pattern.
5. Don't use cone pattern nozzles. They produce a higher portion of extremely small (less than 100 micron) droplets than flat-fan nozzles.
6. Use adequate water. Preliminary studies have shown that 10 gpa and a single fan nozzle can provide adequate canopy coverage as long as proper droplet size and pressure are used. As the crop grows higher spray volumes will be needed.
7. Watch the weather. Applications made when temperatures exceed 90 °F and/or when humidity is low may result in excessive evaporation of smaller droplets. Spraying during windy conditions should be avoided due to drift. Foliage should be dry at the time fungicides are applied. Moisture on foliage (dew) could reduce product efficacy due to dilution or runoff.