Take A Measured Approach To Crop Protection
April 1, 2011 As a pesticide applicator, it is your responsibility to apply the correct amount of pesticide to the target site. If an applicator applies either too little or too much, pest control problems can begin to arise. As an applicator, it is always wise to take the time to establish how much pesticide needs to be applied to the target and then apply the accurate quantity correctly.
There are two common mistakes pesticide applicators make when controlling pests. The first is underdosing. By underdosing, too little pesticide is used and the target may not be fully controlled. As a result, follow up applications may be warranted. The additional time, product and labor put into follow up applications can be extremely costly for the applicator.
Overdosing is equally expensive. As an applicator you do not want to apply more pesticide than the amounts listed in the “Directions for Use” section of the pesticide label. Overusing the recommended amounts listed on the label will not contribute to better control of pests; in fact overusing can help contribute to pesticide resistance. When applying pesticides always remember to follow label directions as the adage says “The Label is the Law”, and by over dosing you can cause environmental and personal injury which can lead to fines and liability for damages.
So how does one decide on how much pesticide to apply? The answer is by studying the “Directions for Use” section of the pesticide label. Under this section you will find information on storage and disposal of the pesticide as well as mixing and application rates. A good rule of thumb to follow is; if the label lists a range of possible amounts, you want to use the least amount of pesticide recommended to achieve desired control of the pest.
The label will also express the amount of pesticide to use. Application rates are most commonly expressed in terms of how much pesticide formulation should be applied. A formulation is a pesticide mixture which is prepared by the manufacturer. The mixture or formulation will include all contents inside the container including the active ingredient plus inert ingredients. Some of the advantages of using a formulated pesticide include ease of application, improved pesticide performance, stability of product and safety. With pesticide formulations, small amounts may be mixed with a larger quantity of carrier such as water so that the pesticide can be applied more efficiently to a large area. Instructions on the label will tell you how much of the pesticide formulation to use and at what rate.
One of the most important precautions you must take when mixing pesticides is to prevent the pesticides from being back-siphoned from the sprayer tank into the well and, subsequently, the ground water. Therefore, the first step is to keep the end of the fill hose well above the water level in the spray tank.
Another safeguard one can take is to locate the mixing/loading site as close to your pesticide storage building as possible. Both the building and the mixing/loading site should be located at least 300 feet from any well or surface water. When mixing the use of an impervious chemical rinse pad or moveable plastic pad is a good idea. With both these pads you can prevent unintentional pesticide spills from contaminating soil or entering ground or surface water.
The use of proper personal protective equipment is also important when mixing pesticides. Be sure to protect yourself from contact to pesticides when mixing. If you are pouring a pesticide from its container, be sure to keep the container below face level. This prevents the pesticide from getting on your face or into your eyes and mouth.
Because mix/loaders work with the product concentrate, and because of the handling activities involved in mixing and loading pesticides, mixer/loaders are subject to more stringent PPE requirements than applicators. Often times this difference will be the addition of eye or full face protection, longer gloves, and a waterproof or chemical-resistant apron
Prior to mixing/loading of pesticides your equipment must be correctly calibrated. Calibrating is a fundamental first step when trying to achieve spray pattern uniformity. Without uniformity, misapplication can take place leading to efficacy concerns, application errors and additional input costs. To calibrate accurately, you must be familiar with the operation of your machinery. Study the manufacture’s directions which should explain how to calibrate the equipment correctly. The instructions should also provide suggestions about the appropriate rate of travel, the range of most efficient pump pressures, approximate settings for achieving various delivery rates, and types of nozzles that can be used.
Let’s look at how to calibrate by using a boom sprayer as an example. Your first step when starting the actual calibration of a boom sprayer is to take time to examine the sprayer, making sure it’s empty and mechanically sound. In this instance you want to examine both the boom and all nozzles and that their tip screens are clean. At this point, you should also note that all nozzle tips on the boom are the same type and size.
After the boom examination is completed, the next step is to put at least 15 gallons of clean water in the spray tank. While typically the amount of spay captured during the calibration procedure works out to be less than one quart per nozzle, you still want enough water to comfortably complete the entire calibration. This also is a good time to check nozzles for leaks.
The calibration tools you will need include a clipboard, paper and pencil, along with a watch with a second hand or a stopwatch. You also will need a hand-held container that holds at least 60 fluid ounces and is marked with U.S. measurement lines.
Start by constructing a data sheet. Include places on the sheet for the equipment, the date, and the pump pressure used during the test. You should also note the type and size of nozzle tip being used and the total number of nozzles. You will also need to note each nozzle’s location on the boom. To do this, begin at the left end of the boom and in order assign a number to each nozzle until all nozzles have been identified. You may want to draw a rough diagram on your data sheet identifying the nozzle order and assigning a number to each one. You will also want to note the amount of time each nozzle is tested (Typically 15 seconds per nozzle) and the amount of water (in fluid ounces) captured from each nozzle.
In a wide open area, start the engine, engage the Power Take-Off (PTO) and run the sprayer pump. Check for any leaks and correct any problems if found. Adjust the regulator until it supplies the same pressure (for instance 30 psi) as will be used in the field. Record that pressure on your data sheet and let the boom continue to spray water.
Measuring Nozzle Tip Performance
Take the clipboard, pencil, watch and catch container to nozzle 1 remembering to start at the left end of the spray boom. Making sure the catch container is empty, place the mouth of the container under the first nozzle and note the time. Hold the container under the first nozzle for exactly 15 seconds. Remove the container from beneath the nozzle tip and note the amount of water in fluid ounces in the container. After recording on your data sheet the amount of spray delivered by nozzle number 1, move to the next nozzle repeating each step exactly the same way until all nozzles have been tested making sure you recorded each individual nozzle output. After you finish measuring each nozzle, be sure to close the boom down and power off the sprayer.
From here you will need to calculate the average nozzle output by using the information you gathered on your nozzle data sheet. The average nozzle output is a benchmark figure.
To arrive at this benchmark figure, add together the total fluid ounces caught from each individual nozzle. After recording this figure on your data sheet, divide the number of nozzles you tested into the total number of fluid ounces recorded. The number you arrive at is the average nozzle output. This is the number you use as your benchmark.
It is not accurate or reasonable to believe that each individual nozzle along a sprayer boom will exactly match the benchmark number, after all no two things are alike. So the question arises how similar should the individual nozzle rates be compared to the benchmark figure.
The answer is the variation between an individual test nozzle’s performance value and the bench mark value should not differ by plus or minus 10%. In other words, if the individual nozzles you tested are not greater or less than the bench mark figure by 10%, the nozzles on your spray boom will not need to be replaced.
Calibrating Example
After adding the output of 6 nozzles, each tested at a 15 second period, it is determined the total nozzle output is 130 ounces. Given an upper and lower 10% variance rate which of the six nozzles will have to be replaced?
Nozzle 1: 25 fluid ounces
Nozzle 2: 20 fluid ounces
Nozzle 3: 21 fluid ounces
Nozzle 4: 18 fluid ounces
Nozzle 5: 24 fluid ounces
Nozzle 6: 22 fluid ounces
Total fluid ounces: 130
Step 1. Establish your bench mark: 130 (total fluid ounces) divided by 6 (total number of nozzles tested) = 21.66 (bench mark)
Step 2. Determine a tolerance value: 21.66 (bench mark) x 10% (variance rate) = 2.16 (tolerance value)
Step 3. Establish an upper limit range: 21.66 (bench mark) + 2.16 (tolerance value) = 23.82 (upper limit of the tolerance range).
Step 4. Establish a lower limit range 21.66 (bench mark) – 2.16 (tolerance value) = 19.50 (lower limit of the tolerance range).
So now we know that the upper tolerance range is 23.82 and the lower tolerance range is 19.50. The final step is to compare the 6 nozzles that were tested to see if they fall within that range. If they do there is no need to replace them. If they fall outside the range, either lower or higher, then you should replace them.
Nozzle 1: 25 fluid ounces (Higher)
Nozzle 2: 20 fluid ounces (Good)
Nozzle 3: 21 fluid ounces (Good)
Nozzle 4: 18 fluid ounces (Lower)
Nozzle 5: 24 fluid ounces (Higher)
Nozzle 6: 22 fluid ounces (Good)
With a systematic approach to analyzing nozzle performance a number of conclusions can be drawn. If a nozzle falls below the lower tolerance range, you can conclude the nozzle is under applying which may signal a clogged nozzle tip. Conversely if a nozzle exceeds the upper tolerance range the nozzle tip may be worn and in need of replacement. The third conclusion is that some nozzles are within the tolerance range and no replacement is needed. Whatever the results indicate, by taking the time to systematically test each nozzle there is a better chance of sprayer uniformity than if no approach was taken at all.
Other sources for calibrating equipment include your local extension agent or informative websites such as http://solutionsforyourlife.ufl.edu/.
No matter what type of equipment you use or the approach to your calibration method, your objective is to measure how much pesticide is to be applied to a certain area. A few simple steps in the calibration process can assure you of accuracy. One step is to check calibration often, never assuming that it will keep on delivering the same rates during upcoming applications. If you are using a dry formula use a scale to weigh out the exact weight you need. Use measuring spoons or a tip and pour measuring devise to measure teaspoons or tablespoons. If you are going to measure from ¼ cup to 1 pint, use a graduated device such as a measuring cup. To measure from 1 pint to 5 gallons use a graduated jug or pail for amounts, above 5 gallons a flow meter should be used.
Applying the correct amount of pesticides to a targeted area is a step-by-step approach which can assure the applicator of ongoing success. By abiding to label instructions, the applicator can prevent either over or under dosing, preventing additional expenses and potential pest resistance. Mixing and loading and calibration are also important applicator considerations. Proper mixing can prevent personal injury, while careful calibration will provide for the pesticide applications to accurately be applied to the target site.
It is the applicators responsibility to combine correct product use information, and safe mix/load procedures with equipment that is in good operating condition and properly calibrated. When the applicator has pieced together these important elements, proper steps have been taken towards assuring the success of a effective pest control program.
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