Spray equipment calibration and water volume
Accurate water volume calibration ensures uniform chemical distribution without under-dosing or foliar runoff.
- Calibrate with Clean Water: Measure water output across a measured test area before adding any chemical to determine precise sprayer output per acre.
- High-Volume Spraying (Knapsack): Typically requires 150 to 200 liters of water per acre for field crops and 300 to 500 liters for orchards.
- Low-Volume Spraying (Power Sprayers): Requires 60 to 100 liters of water per acre; uses concentrated fine mist.
- Avoid Under-Dosing: Under-dosing exposes insects to sub-lethal concentrations, accelerating chemical resistance development.
Nozzle selection and droplet size management
Matching nozzle design to target pest locations ensures chemical reaches hidden insects.
- Hollow Cone Nozzles: Produce fine circular mist droplets (100 to 250 microns); best for insecticides and fungicides requiring complete leaf wetting.
- Droplet Size: Extremely fine droplets drift away in wind; excessively large droplets bounce off leaves and waste chemical onto soil.
- Canopy Penetration: Direct nozzles to hit both upper and lower leaf surfaces, particularly for sucking pests like aphids, thrips, and whiteflies.
- Clean Nozzles: Use a soft nylon toothbrush or water jet to clean clogged tips; never use metal pins that distort orifice symmetry.
Weather conditions and personal protective equipment
Environmental factors and operator safety determine spray efficiency and health safety.
- Weather Timing: Spray during early morning (6:00 to 9:00 AM) or late afternoon (4:00 to 6:30 PM); avoid spraying during strong winds, midday heat, or imminent rain.
- Mandatory PPE: Wear chemical-resistant rubber gloves, safety goggles, face respirator or mask, rubber boots, and long-sleeved clothing.
- Never Spray Against Wind: Always spray with the wind at your back to prevent chemical mist from blowing onto your body.
- Triple-Rinse Containers: Rinse empty chemical containers three times, pour washings into the spray tank, puncture containers, and dispose of them safely.
Official source
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Central Insecticides Board & Registration Committee (CIBRC) ↗Related on KisanPe
Common questions
Which nozzle is best for spraying insecticides on field crops?
A hollow cone nozzle is the best choice for insecticides because it produces fine droplets that penetrate the canopy and coat both upper and lower leaf surfaces.
Why should farmers avoid spraying insecticides during midday heat?
Midday heat causes rapid evaporation of spray droplets, increases thermal air updrafts that blow chemicals away, and can cause leaf scorching (phytotoxicity).
What is the pre-harvest interval (PHI) for an insecticide spray?
The pre-harvest interval is the mandatory minimum number of days that must elapse between the last chemical spray and harvesting produce to ensure safe residue limits.
General guidance, not personal advice. For your farm, ask your local Krishi Vigyan Kendra or agriculture officer.
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