By Erdal Ozkan
This is the time of the year you must complete shopping for nozzles because the spraying season is just around the corner. Although nozzles are some of the least expensive components of a sprayer, they hold a high value in their ability to influence sprayer performance. Nozzles help determine the gallon per acre. They also influence the droplet size, which plays a significant role in achieving improved penetration into crop canopy and better coverage on the target pest, both affect the efficacy we expect from pesticides applied.
When I get a question like, “What is the best nozzle I can buy?” my answer is: it depends on the job on hand. One nozzle may be best for a given application situation, but it may be the worst nozzle to use for another situation. Sometimes, the choice of nozzle may be determined by the requirements given on the pesticide label.
Selecting the best nozzle requires careful consideration of many important factors including: sprayer operation parameters (such as application rate, spray pressure, travel speed); type of chemical sprayed (herbicides, insecticides, fungicides); mode of action of chemicals (systemic, contact); application type (broadcast, band, directed, air assisted); target crop (field crops, vegetables, vineyard, shrubs and trees, etc.); and spray drift risk. I will briefly cover some of these topics in this article. For detailed information on nozzle selection, I strongly recommend you read a new Ohio State University Extension Publication titled “Selecting the Best Nozzle for the Job.” In this publication, you will see step-by-step guidelines for selecting the most appropriate spray nozzle for a given application situation. The publication is available online at: http://ohioline.osu.edu/factsheet/fabe-528.
Each nozzle type is designed for a specific type of target and application. For example, a nozzle designed for broadcast spraying is not good for spraying pesticides over a narrow band. While one nozzle may be best for a given situation, it may be worst choice for another. Ohio State University has conducted field experiments to determine which nozzles to choose for two different application situations: soybean diseases such as rust and white mold, and wheat diseases such as head scab and stem rust. We included six to eight different nozzles in the experiments. We found out that while a twin-fan pattern nozzle was best for controlling wheat head scab, the same nozzle turned out to be the worst choice to protect soybeans against rust and white mold when the soybean canopy is tall and dense. So, before buying the nozzles and putting them on the boom, check the nozzle manufacturers’ catalogs which have charts showing which nozzle type will be best for a specific job. Check the websites of nozzle manufacturers to reach their catalogs.
Once you determine the type of a nozzle you need to buy, you also must buy the right size of that nozzle which will satisfy the application rate (gallons per acre or gpa) you wish to use as you do your spraying at different travel speeds. Nozzle catalogs are filled with tables and charts showing application rates, given a nozzle’s flow rate (gallons per minute or gpm) delivered at various pressures (psi) and travel speeds (mph). However, the charts are only for a limited number of travel speed and nozzle spacing situations. Most nozzle manufacturers have developed Apps for smart phones that provide you the exact nozzle flow rate required for any given set of application parameters, and identify a specific set of nozzle recommendations for the given application parameters. To find these Apps, simply visit the App Store in your smart phone or tablet and do a search under “Spray Nozzle Calculator” or some other key words related to nozzle size selection.
Keep several types of nozzles on the boom
Remember that one specific type of nozzle will not be best for all applications. For this reason, it is best to have several types and sizes of nozzles on the boom so that you can switch to the “best” nozzle choice for a given spraying job. There are various types of sprayer components and setups you can buy to configure your boom so the new set up allows you to easily switch from one nozzle to another instantly.
Keep spray drift in mind when selecting nozzles
Spray drift (movement of pesticides by wind from the application site to an off- target site) is a serious problem for many reasons. Extensive information related to factors influencing creation of spray drift, is provided in the Ohio State University Extension publication FABE-525 (http://ohioline.osu.edu/factsheet/fabe-525). After wind speed and other weather-related conditions, choice of nozzles is the second most influential factor affecting drift. Research conducted at The Ohio State University and elsewhere clearly indicate that nozzles labeled as “low-drift” significantly reduce spray drift. If drift is, or becomes a concern, it may be best to switch from a conventional nozzle to a “low-drift” version of the same type nozzle with the same flow rate. This is another good reason to have more than one type of a nozzle on the boom.
Give special attention to choice of nozzles when applying pesticides containing 2,4-D and Dicamba
The labels of 2,4-D or Dicamba herbicides include specific requirements on which nozzle or nozzles must be used when spraying these products. The requirements also include a range of operating pressures for each one of these nozzles. These strict requirements are put on the labels to avoid off-target movement (drift) of spray droplets. Simple interpretation of these requirements is: you would be violating the pesticide label, therefore the law, if you use any other type and size of nozzle and operate these nozzles outside the pressure ranges. Remember, the label is the law! So, it is your responsibility to comply with the requirements on pesticide labels. You can reach a list of currently approved nozzles and their operating pressure ranges on labels of the several commonly used 2,4-D and Dicamba products at this web site: https://pested.osu.edu/sites/pested/files/imce/ApprovedNozzles.pdf.
The table at this site is provided mostly for information purposes and may not be up to date. So, check the manufacturers’ websites, and read the product label for the most current information. Do not assume that you do not have to worry about checking the label because you had applied the same product in a previous year. A nozzle required for the same product last year may not be on the label this year, or the operating pressures might have been changed.
Some final thoughts
Nozzles are typically the least costly items on a sprayer, but they play a key role in the final outcome from a spraying job: achieving maximum efficacy from the pesticide applied while reducing the off-target (drift) movement of pesticides to minimum. Pesticides work well if the rates on labels are achieved during application. This can be achieved only if the right nozzle type and the proper size of the nozzles are on the sprayer, and the sprayer is operated properly.
Erdal Ozkan, Professor and Extension ag engineer, can be reached at 614-292-3006, or firstname.lastname@example.org. This column is provided by the OSU Department of Food, Agricultural and Biological Engineering, OSU Extension, Ohio Agricultural Research & Development Center, and the College of Food, Agricultural and Environmental Sciences.