Crop and Pest Management Guidelines

7.11. Cleaning Sprayers

Sprayers must be thoroughly cleaned inside and out after use and before storage. Ideally, a sprayer should be cleaned at the end of each day and especially before switching to a different pesticide. Pesticide residues left on the outside of the sprayer can cause operator exposure. Residues on the inside of the tank or leftover pesticides trapped inside the sprayer plumbing system can contaminate the operator and possibly lead to crop damage. Growers should be concerned about this, especially if they are using one sprayer to apply different chemicals to different crops. In some cases, only a small amount of a pesticide remaining in the sprayer can cause significant crop damage or lead to unacceptable residues on a crop. Crop contamination can even occur several months after a sprayer has not been properly cleaned. Where a sprayer is used to spray different fruit crops, residue left in the tank can cross contaminate another fruit crop, potentially causing illegal or unwanted pesticide residues, making the crop unmarketable.

Sprayers can also retain tremendous amounts of pesticide solution. Depending on the size and design of the sprayer, there can be nearly 6 gallons of solution left in a sprayer's plumbing. As illustrated in Table 7.11.1, research conducted on boom sprayers has shown that, depending on the spray tank size, the total chemical solution retained in the sprayer ranged from just under 3 gallons to over 12 gallons. The parts that retained the most chemical solution are the chemical induction bowl, the booms, the tank and the pump and its related piping.

Tests have shown that triple rinsing the spray tank is better than using just one single rinse. For example, using 100 gallons of clean water in one single rinse to clean a 100-gallon sprayer tank reduced the concentration of the original spray solution from 100% to 5% both in the tank and at the nozzle. If triple rinsing was performed using 33 gallons of clean water per rinse, a concentration of 0.2% to 0.5% was gained. The aim is for maximum dilution with minimal use of water. Table 7.11.2 illustrates how triple rinsing reduces the pesticide concentration at the nozzle and the tank drain.

Before rinsing a sprayer, read the sprayer manufacturer's instructions for specific guidance on the best methods for cleaning your equipment. Also consult the pesticide label for any special cleaning instructions. When cleaning spray equipment, you should use the protective clothing listed on the pesticide label. Sprayer cleaning should be done so that rinse water does not enter any waterway, field drainage system, or well. Ideally, sprayer rinsate should be applied to a labeled crop at labeled rates. If rinsing needs to be done at the mixing/ loading site, it must be done on an impervious surface. All contaminated rinse water must be trapped and either used to mix another load of the same pesticide at the label recommended rates or disposed of at an approved pesticide waste handling facility.

7.11.1 Reducing Cleaning Problems

The need for cleaning can be reduced by good planning and equipment maintenance. The following are suggestions to help reduce cleaning needs:

• Carefully plan how much pesticide to mix so that all mixed pesticides are used up when you are finished with the field.
• Be sure that the sprayer is clean before you use it.
• Make sure all parts of the sprayer are in good condition. Corroded, cavitated or pitted surfaces are prime areas for pesticide residue to hide. Replace any worn parts.
• Mix the chemicals in the correct order. Some chemicals, when mixed in the wrong order, can actually become more difficult to remove from the equipment. Consult the pesticide label for the proper mixing order.
• Follow any label instructions for cleaning spray equipment.
• Be sure that cleaning solutions contact ALL equipment surfaces.
• Remove and clean filters, strainers and nozzle screens separately from the rest of the sprayer.

7.11.2 Sprayer Cleansers

Several sprayer cleansers are commercially available. These cleansers should be selected based on the pesticide formulation used. Specific recommendations can be found on the pesticide label, by contacting the pesticide manufacturer or through the label or manufacturer of the cleaning agent you wish to use. Some available cleansers are listed in Table 7.11.3. Household detergents, such as laundry soaps and household ammonia, can also be used, but they may not adequately deactivate and solubilize the pesticides for effective cleaning. Chlorine bleach solutions should not be used. Cleaning agents can be used to wash both the inside and outside of the sprayer. When using commercial cleansers, follow the product's instructions for the best results.

7.11.3 Tank Rinse Systems (Low-Volume Tank Rinsing)

Tank rinse systems consist of a clean water supply tank mounted to the sprayer and one or more rotating discs or nozzles mounted inside the main sprayer tank. Water is pumped from the clean water tank to the rinse nozzles where the water is sprayed around the inside of the spray tank. These systems are designed for in-field rinsing of the sprayer so that the tank washings can be applied to the field and reduce the amount of time spent traveling.

A tank rinse system can be purchased as an option on some sprayers or as an add-on kit. Rinse systems can also be made from readily available parts and installed on the sprayer. A sample rinse system layout is shown in Figure 7.1.1. A typical rinse system uses 360-degree tank wash nozzles mounted in the top of the tank. These nozzles are available in flow rates of 10 gallons of water per minute at 20 psi up to 20 GPM at 50 psi. If a spray tank has baffles, at least one rinse nozzle per compartment should be provided. In any case, a sufficient number of rinse nozzles should be installed to provide enough rinse water to contact the entire tank interior.

A clean water tank can be plumbed into the sprayer plumbing system to provide the clean rinse water. This tank should be permanently marked "Clean Water Only" so that only clean water is placed in the tank, reducing the chance for contamination of the rinse system. The tank should be mounted above the pump in order to aid in priming the pump. Ideally, the tank should be mounted on the sprayer.

When using tank rinse systems, you may want to check the pesticide label or with the chemical manufacturer to be sure that low-volume rinsing is suitable for the products you're using. Also, during the rinse process, be sure to open and close the pressure valve and other control valves on the sprayer to ensure that any chemical that may be trapped in the valve is rinsed out, further reducing the chance for contamination of future pesticide mixes. To obtain the best results, practice using the rinse system by placing spray marker dye or food coloring in the spray tank. Using the rinse system, run three rinse cycles, making sure the water discharged from the nozzles is completely clear by the end of the third rinse.

Figure 7.11.1. Sample layout of a sprayer rinse system

Figure 7.11.2. Two types of 360-degree tank rinse nozzles

7.11.4 Sprayer Cleaning and Maintenance

Sprayers must be decontaminated thoroughly, inside and outside, after use. Regular maintenance of spraying equipment will prolong its life and ensure accurate trouble-free operation, enabling spraying to be done with the minimum loss of time and taking full advantage of favorable weather conditions.

REMEMBER: Clean up so washings DO NOT enter public sewers, water bodies, fields that have underdrainage, and wells.

Try to keep the volume of tank washings produced to a minimum. Special low-volume washing systems are now available and should be used. Tank washings may be usable as a diluent when mixing a further batch of spray.

NOTE: Read the sprayer manufacturer's instructions before beginning to wash out a sprayer. Wear protective clothing as listed on the pesticide label.

To clean a rotary atomizer sprayer, rinse out the tank, drain all the unused spray from the system and run the atomizers empty for a short time. Wash out the sprayer with detergent and water or recommended cleansing fluid, making sure that all atomizers are thoroughly clean, and using a brush if necessary. Carefully clean off the outside of the sprayer, drying any electrical connections to prevent the penetration of damp. Oil where necessary.

With all types of sprayers, if frost is likely, thoroughly drain the spray system, paying particular attention to the pump casing and valve galleries, and ensure that all low points where liquid may be trapped are adequately drained. Filter caps and bodies may be stored in the filter basket, along with any drain plugs that have been removed.

In addition to the sprayer, the same care must go into cleaning the protective equipment you wear, associated equipment such as bowsers and mixers, the site where filling and mixing is done, the tractor and of course yourself and any other person involved. Wash reusable protective clothing and remove and store it where it can dry off. Follow any manufacturer's directions on cleaning as well. Shower and change into clean clothes. See inside the back cover of this publication for tips on cleaning pesticide-contaminated clothing.

There are two levels of sprayer cleaning to consider:

• When similar products or products compatible with the crop to be treated are to be used on successive occasions, within a period of spraying activity.
• When one type of product is changed for another, such as an herbicide to an insecticide, or when products are incompatible with the crop to be treated, or at the end of the season.

7.11.5 Cleaning when Similar Products are to be Used

Always wear the protective clothing on the label or if none listed, at least rubber gloves, coveralls, boots and a face shield.

• The last load in the spray tank should be just large enough for the area left to be sprayed. Before cleaning, correctly dispose of any leftover spray liquid. Spray liquid can be left to stand overnight provided cleaning is done early the next day, but note instructions for products containing solvents that may damage hoses, diaphragms etc. if left in the sprayer.
• Remove tank drain plugs or open drain cock.
• Hose down the tank, inside and out, including the underside of the tank top. Scrub where necessary or use a special low volume washing system.
• Replace drain plug.
• Remove suction, main and in-line filter elements; wash them thoroughly in clean water with a soft brush and replace.
• Remove nozzles, nozzle filters and nozzle bar end-caps if they are fitted. Soak them all in a bucket of water with the appropriate cleaning agent recommended by the manufacturer of the product that has been used.
• Partially fill the tank and pump out to flush all parts. Do this more than once if necessary.
• Refit nozzles, filters, and other parts.
• Hose down the outside of the sprayer and tractor, scrubbing if necessary.
• Wash down waterproof clothing, apron, boots and face shield. See inside back cover for tips on cleaning pesticide-contaminated clothing.
• Return unused product to the storage.
• Wash inside and outside of gloves with soap and water; rinse and dry them.
• Thoroughly wash hands, face, and neck with soap and water and complete record sheets.

7.11.6 Cleaning when Product Type is Changed

This procedure also should be followed at the end of a season or before machine maintenance. Always wear the protective clothing listed on the pesticide label or if non is listed, at least rubber gloves, coveralls, boots and a face shield.

• Correctly dispose of any spray liquid or contamination left in the tank.
• Remove tank drain plugs or open drain cock.
• Hose down the tank, inside and out, including the underside of the tank top. Scrub where necessary or use a special low-volume washing system.
• Replace drain plug.
• Remove suction, main and in-line filter elements; wash them thoroughly in clean water with a soft brush and replace.
• Remove nozzles, nozzle filters and nozzle bar end-caps if they are fitted. Soak them all in a bucket of water with appropriate cleaning agent recommended by the manufacturer of the product that has been used.
• Partially fill the tank and pump it out to flush all parts. Do this more than once if necessary.
• Refill the tank with clean water and pump it through the pipes and spray bars. Leave for as long as practicable, overnight if possible.
• Discharge at least one quarter of the contents of the tank through the system and spray bars. Drain off the rest.
• Check that no deposits remain in the tank or filters. Any that remain should be hosed down and scrubbed off.
• Repeat steps 8 to 10 using clean water with the appropriate cleaning agent recommended by the manufacturer of the product that has been used.
• If stubborn deposits still remain, possibly resulting from mixture incompatibility, repeat the washing using 2 lbs. washing soda plus 1.5 fl. oz. Agral per 25 gallons of water. Better results are obtained with warm or hot water.
• If changing from one type of product to another, refit nozzles, filters, etc.
• After seasonal cleanups, safely store nozzles and filters, and leave valves open and the tank lid loosely closed. If leaving the sprayer unattached, ensure that it is parked safely and securely in a stable position.
• Hose down the outside of the tractor and sprayer, scrubbing if necessary.
• Wash down waterproof protective clothing, apron, boots and face shield. See inside back cover for tips on cleaning pesticide-contaminated clothing.
• Wash inside and outside of gloves with soap and water; rinse and dry them.
• Thoroughly wash hands, face and neck with soap and water.

7.11.7 Disposal of Pesticide Waste

The safe disposal of pesticide waste is a serious responsibility for pesticide users. Therefore, it is important to keep the amount of waste generated to a minimum.

Pesticide waste is of four types:

• Concentrated products.
• Diluted pesticides, including washings.
• Empty containers.
• Contaminated clothing and other materials.

7.11.8 Storage of Sprayers

Store sprayers carefully after use. Follow the manufacturer's specific instructions. If none are available, use the following general guidelines:

• Thoroughly wash the sprayer inside and out with water, followed by a solution of detergent and water, followed by water. Drain thoroughly. Allow air access to all parts of the sprayer system. A more thorough decontamination routine is outlined earlier.
• Inspect filters, nozzles, hoses and all other components, and order all necessary spares.
• Pay particular attention to the pump. Inspect rollers or diaphragms and valves and order necessary spares.
• Check the soundness of all mechanical parts, particularly the booms and boom hinges, and wheels.
• Store sprayer under cover, taking care to prevent dirt and moisture affecting the tank or working parts.

CAUTION

All mounted sprayers tend to be unstable when removed from their tractors. Make sure sprayers are safely chocked before leaving them.

7.10 Going Spraying! Mixing Procedures

7.12 Spraying Small Vineyards