Northeast Region Certified Crop Adviser (NRCCA) Study Resources

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In This Section

• PO 46 Spray Drift
• PO 47 Particle drift
• PO 48 Spray droplet size
• PO 49 Modes of entry
• PO 50 Chronic & acute poisoning
• PO 51 Acute pesticide poisoning symptoms
• PO 52 Chronic effects of pesticide poisoning
• PO 53 Pesticide contact procedures
• PO 54 Material Safety Data Sheets
• PO 55 Protective gear
• PO 56 Cleanup procedures
• PO 57 Disposal methods
• PO 58 Safe storage
• PO 59 Spill procedures

Competency Area 8: Protecting Humans from Pesticide Exposure

PO 48. Know factors that affect spray droplet size:

A. Spray pressure
B. Nozzle size
C. Spray rate (gallons per acre)
D. Drift control agents (foams, invert emulsions, spray additive stabilizers, etc.)

Droplet size is the most important factor affecting the potential for particle drift and that smaller droplets drift farther than large droplets. Spray droplets less than 150 microns in diameter are more prone to drift and droplets less than 50 microns being highly susceptible to drift. (For reference, 50 microns is about the diameter of a human hair.) There will always be a range of droplet sizes in any spray pattern. You cannot eliminate small droplets but you can reduce the proportion of them in the spray once you know what affects droplet size.

A. Spray pressure
Increased spray pressure increases the number of small droplets produced. Keep the pressure as low as possible within the range for the nozzle and product you are using.
B. Nozzle size
Nozzles with larger openings or narrower spray angles will produce fewer fine droplets. Using wider spray angles may allow you to bring the nozzles closer to the target surface. Doing so more than compensates for the finer spray. Some nozzles (such as a turbo flat-fan or air induction nozzle) are specifically designed to produce fewer fine droplets.
C. Spray rate (gallons per acre)
Higher spray rates (gallons of spray mix per acre) let you use nozzles with larger openings. Thus, if you need to increase spray rates, use larger nozzles rather than increasing spray pressure.
D. Drift control agents (foams, invert emulsions, spray additive stabilizers, etc.)
Drift reduction adjuvants such as foams, invert emulsions, or stabilizers reduce the number of small spray droplets but they will also reduce coverage of the plant surface. Be sure to use adjuvants according to the directions on the pesticide label to avoid problems. A pesticide label may require the use of drift-reduction agents under certain conditions, such as low application rates.