There are several factors that need considered when making a proper spray application, such as; pesticide selection targeting the hardest to control pest in the field, using the correct nozzle for the target pest, applying adequate carrier volume to ensure coverage, boom height matched to your nozzles requirements, utilizing the correct adjuvants as required by the pesticide.
One of the most critical factors in a quality spray job is the spray nozzle. It is important to note that not all nozzles are created equal and there are several factors to consider when choosing a nozzle.
The first question to ask is, "what am I spraying"? This question is really two fold. What is the target of application and which chemistry are you going to use? The answer to these questions will greatly determine the nozzle you need to run. But before we delve deeper, lets identify two critical factors.
Systemic versus Contact
- Systemic chemistries are those that absorb into plant material and then translocate into different parts of the plant through the vascular system. They either move into the Phloem or the Xylem. Fancy words, but important to note that the Xylem moves "up the plant" and the Phloem moves "from the leaves" up and down the plant. Either way, a pesticide enters the plant and moves to somewhere else within the plant.
- Contact chemistries are just that, contact. They generally do not move within the plant and bind to a localized area from where the spray droplet is deposited.
Why this matters
Contact herbicides require a great deal of coverage to work. Literally, we must deliver a final spray solution to every possible part of the target plant. That means higher spray volumes and smaller droplets.
Whereas, systemic herbicides can "get by" with lower spray volumes and bigger droplets. This does not mean that we can sacrifice volume significantly.
With the advent of Dicamba and 2,4-D tolerant crops, there are some special requirements that must be satisfied in regards to nozzle selection. Consult the product label, Monsanto Application Requirements, BASF or DOW for a list of "approved" nozzles.
Generally, these nozzles all produce very course to ultra course droplets as the main concern is physical drift. EPA regulations dictate the usage of these nozzles and other adjuvants because of off target drift potential. These nozzles help reduce the smaller droplets that can move with wind. Lets take a moment to look at a couple of distinctions about "off target" applications.
Physical versus Volatilization
Physical drift occurs when the actual spray solution is moved off target. This can happen by wind or temperature inversions.
Volatilization happens when the liquid chemistry turns to gas vapor (fog) and moves off target. Certain chemistries are susceptible to "gas off" when temperatures are above 85 degrees and humidity is relatively high. This process can happen several days after application. Classic examples of type of chemistries are DMA salt of dicamba and 2,4-D ester's.
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- Contact chemistries generally need 15-20 gallons of final spray solution
- Systemic chemistries generally need 10-12 gallons of final spray solution
- Heavier canopies need more volume regardless of chemistry.
Adjuvants are things that we add to our spray solution to increase its effectiveness. Understanding the role they play in producing a quality application are key. Common adjuvants used include: Non Ionic Surfactants (NIS), Crop Oil Concentrates (COC), High Surfactant Crop Oil Concentrates (HSCOC), Metholated Seed Oil (MSO) and Water Conditioners like Ammonium Sulfate (AMS).
It is important to note that not all adjuvants are created equal as regulations are much different with adjuvants than pesticides. Look for adjuvants that have been certified by Council of Producers and Distributors of Agrotechnology (CPDA).
Please check out the following links for more information on Adjuvants and CPDA certificiation
Application boom height is commonly overlooked but extremely important. Depending on the spacing of your nozzles, 15 inch or 20 inch, will greatly determine the boom height that you will need to run. There is a certain degree of overlap required to ensure that the spray solution is even distributed over the target. Make sure your booms are parallel to the ground where ever possible. Consult your nozzle manufacture for information on how high your booms should be. A good rule of thumb is 24-28 inches above your target.
It is also important to note that boom height has a direct correlation to the distance of physical drift potential. Generally, the closer the nozzle is to the ground, the less distance the droplet can travel resulting in the reduction of physical off target drift potential. Remember that spraying with the booms up in the air in the classic "V" formation is not a good strategy for managing off target drift.
If you need more detailed information pertaining to Sprayers, Nozzles and/or Adjuvants , please let us know.