How Spray Nozzles Affect Your Product Performance

Why spray nozzle type is important 

Selecting the improper nozzle type can reduce herbicide, fungicide, and/or insecticide performance and result in reduced product efficacy.

How droplet size has a dramatic effect on spray coverage

The small flower morning glory leaf pictured below shows the influence of doubling spray droplet size. Logic suggests that droplet numbers would be cut in half. In reality, when droplet size is doubled, droplet number decreases 8-fold.

Spray Nozzle Recommendation

Unless label requirements specify (over-the-top dicamba herbicides) it is recommended to avoid nozzles that produce droplet sizes ≥ 500 micron (µm). However, with addition of a nonionic surfactant (NIS) or other adjuvant containing spreader agents, coverage from 500 µm droplet size nozzles perform similar to 250 µm spray size.

Preemergence pesticide applications

Research suggests improper nozzle selection is more forgiving with preemergence applications. Researchers in Missouri and Mississippi showed droplet size did not influence preemergence herbicide efficacy when applied in 15 gallons per acre (GPA) spray volume. The only exception where weed control varied was on unsettled ground. In this instance twin-fan nozzle improved weed control.

Nozzle selection for preemergence applications should be chosen because they provide fully overlapped coverage.

Preemergence application

Regardless of nozzle selection, plan preemergence applications within 24 hours of a rainfall or irrigation event to ensure product activation. Consider using an adjuvant like Venturi® to enhance preemergence herbicide efficacy for problematic pest control.

Postemergence application

Postemergence applications are greatly influenced by nozzle selection. Whether applying an herbicide, insecticide, or fungicide, a balancing act between selecting a nozzle that will provide adequate coverage with minimal off target movement is key. Nozzle types that have a volume median diameter (VMD) of 300-450 µm are recommended regardless of spray application.

How to select nozzle type for application

The above figure should be helpful in selecting nozzles for different herbicide applications. Systemic products that move throughout the plant don’t require as much coverage when compared contact active products (whether an herbicide, insecticide, or fungicide).

However, greater coverage with systemic products is beneficial. Research has demonstrated that droplet size has less impact on efficacy of postemergence herbicides, so long as the VMD doesn’t exceed 700µm.

Are there application restrictions?

Dicamba or other label restricted applications Over-the-top (OTT) dicamba and 2,4-D applications require the use of certain nozzles and pressures. With OTT auxin herbicide applications, nozzle selection becomes more restrictive, but growers can still maximize product performance with other adjustments to spray applications.

Surface tension and spreading 

As referenced earlier, if applications require a nozzle that gives one droplet in the same area that could have had 64, optimal performance is paramount. Increasing the spreading and deposition capabilities through adjuvant selection are critical with larger spray droplets.

Breaking surface tension of larger spray droplets will increase coverage and help maintain product efficacy. With dicamba and/or 2,4-D applications, ensure that whatever adjuvant decided upon is labeled for use with that product.

The Takeaway

The correct nozzle and adjuvant pairing may increase success for pest problems. Please consult any of your local Agronomic Sales Enablement Team or your local Simplot Grower Solutions Crop Advisor to answer your application questions. 

Authors

Ben Lawrence, Bayou
Jeffrey Mansour, Midsouth
Justin McCoy, Southwest

Click to read more about the authors