Top 10 tips for better spraying

By Erdal Ozkan Professor and Extension State Specialist, The Ohio State University

Applying pesticides requires a high level of skill and knowledge. Over the years, sprayers’ increasing size and complexity have necessitated even more attention to efficiency, efficacy, and safety when spraying pesticides. Although each crop requires a slightly different approach to pesticide application, some general principles apply to nearly all spraying situations. Here are my top 10 recommendations (not in any particular order) that will make spraying efficient and effective, resulting in a higher level of biological efficacy expected from pesticides applied:

1. Select the best nozzle type and size for the job. Although each component of the sprayer plays a role in achieving success in pesticide application, nozzles have the most significant impact. Nozzles are available in various types and sizes, each designed for a specific target and application. Most manufacturers’ catalogs and websites feature charts showing which nozzle type is best for a particular job. Any of the following factors may be decisive when selecting the most appropriate nozzle: sprayer operation parameters (application rate, spray pressure, ground speed); the type of chemicals applied (herbicide, insecticide, fungicide, fertilizers); the mode of action of the chemical (systemic or contact) for spray coverage requirements; application type (broadcast, band, directed, air-assisted); risk of spray drift; and specific nozzle or droplet size requirements noted on the product label. Once you determine the best nozzle for a particular spraying situation, you need to identify the appropriate size of that nozzle to provide the application rates (gal/acre) prescribed by product labels under various operating conditions (spray pressures and travel speeds). More information on selecting nozzle type and size is outlined in Ohio State University (OSU) Extension publication FABE-528, “Selecting the Best Nozzle for the Job“.

2. Carefully read and follow the specific recommendations provided in sprayer operators’ manuals and on the labels of applied pesticides. Remember, what is required on a label is the law. For example, the labels of 2,4-D or Dicamba herbicides include specific requirements for nozzles and operating pressure ranges. If you use a different type or size of nozzle and operate outside the pressure range specified by the pesticide manufacturers, you are violating the pesticide label, and thus the law. Remember, the label is the law!

3. Keep spray drift in mind when spraying. Although complete elimination of spray drift is impossible, problems can be significantly reduced by being aware of the significant factors that cause drift and taking precautions to minimize their influence on the off-target movement of droplets. The nozzle you select and the weather conditions at the time of spraying are the two most influential factors affecting the generation and reduction of spray drift. Keep nozzles as close to the target as possible while still producing a uniform distribution of spray on the target. If weather conditions (wind speed and direction, humidity, temperature, inversions) are unfavorable, and there is concern about spray that might result in drift, wait until that element of doubt is resolved. Extensive information related to factors influencing spray drift is available in OSU Extension publication FABE-525. “Effect of Major Variables on Drift Distances of Spray Droplets.“

4. Maximize pesticide deposit and coverage on the target, which may vary across different parts of the crop canopy. For example, when applying a fungicide to manage Fusarium head blight or “head scab” on small grains, the target is the head, not the leaves. Conversely, when spraying for soybean sclerotinia stem rot (white mold), the most critical area requiring treatment with fungicides is where flowering occurs. Nozzle selection greatly influences whether the droplets reach the specific target location in the canopy. For instance, twin-pattern nozzles or a single flat-fan nozzle tilted at a forward angle of 30 to 45 degrees down from the horizontal are ideally suited for applying fungicides for wheat head scab. However, it is the least effective setup for soybean insects and diseases, such as aphids and white mold.

5. Slow down when spraying. Spray coverage is usually better at slower speeds. The higher the travel speed, the greater the likelihood of spray drift.

6. Calibrate the sprayer. A sprayer can only be effective, efficient, and safe if it is properly checked and calibrated well before it is taken to the field and periodically during the spraying season. Some may argue that most sprayers are now equipped with sophisticated rate controllers and ground speed sensors, making calibration unnecessary. Unfortunately, not all electronic controllers can detect flow rate changes on each nozzle on the boom, and none can detect changes in the spray pattern. The primary goal of calibration is to determine the actual application rate in gallons per acre and then make adjustments if the difference between the actual rate and the intended rate is greater or less than 5% of the intended rate. There are several ways to calibrate a sprayer. One easy method is explained in the OSU Extension publication FABE-520, “Calibrating Boom Sprayers.” Be safe. Wear protective clothing, goggles, rubber gloves, and respirators, if required, on the label when calibrating the sprayer, spraying, and cleaning the equipment.

7. Check for uniformity of application. The uniformity of chemical deposition on the target is as important as the amount applied. Maintain consistent deposition of spray material across the entire width of the target area. Non-uniform coverage results from misaligned or clogged nozzles, nozzles with varying fan angles, or uneven nozzle height along the boom. These common issues lead to streaks, untreated areas, or over-application of chemicals.

8. Understand how to calculate the amount of chemical product to mix in the tank. Even if your sprayer is in good condition and calibrated regularly, using the incorrect amount of chemical in the tank can lead to unsatisfactory pest control. Detailed information on how to calculate the proper amount of chemical to add to the spray tank is provided in the OSU Extension publication FABE-530, “How Much Chemical Product Do I Need to Add to my Sprayer Tank?”

9. Take advantage of technological advancements in spray technology, such as GPS, automatic guidance systems, and independent control of nozzles using PWM (Pulse Width Modulation). Update and upgrade your sprayer with these technologies, which can be easily integrated into your existing sprayer.

10. Consider using a sprayer with an air-assisted boom when coverage in the lower parts of the canopy is crucial for controlling certain insects and diseases, particularly in full, dense canopy conditions, like soybeans sprayed in the late season.

For more information on this topic, please read the OSU Extension publication FABE-532, “Best Practices for Effective and Efficient Pesticide Application.” Don’t hesitate to contact me if you have a specific question that was not addressed in this article or any of the other OSU Extension publications I mentioned in this article.

Happy spraying!

Erdal Ozkan, Professor and Extension ag engineer, can be reached at ozkan.2@osu.edu. This column is provided by the OSU Department of Food, Agricultural and Biological Engineering, OSU Extension, and the College of Food, Agricultural and Environmental Sciences.

This is part one of a two-part series from Erdal Ozkan. Part two can be found here.