Improper or inadequate cleaning of sprayers following the application of Group 2 herbicides can cause significant damage to canola and other susceptible crops. If not cleaned out thoroughly, residue can hang around in the sprayer tank, nozzles or screens.

Tom Wolf, a research scientist at Agriculture and Agri-Food Canada at Saskatoon, Sask., has done extensive research into sprayer cleanout procedures, and says that it’s not only important to be thorough when cleaning out the sprayer, but it’s also important to know when it’s necessary to be especially careful. “You need to know what’s in the tank,” says Wolf. “And you need to know what kinds of products may cause you problems and which ones won’t.”

There are hundreds of herbicides on the market, says Wolf, and because of the proliferation of different brand names containing the same active ingredients, it’s not always easy for farmers to know what the active ingredient is. With tank mixing now deregulated by the Pest Management Regulatory Agency applicators could also encounter some incompatible mixes. “Producers have to educate themselves and know when to be careful,” says Wolf. “Once you have identified a possible problem then you have to take the appropriate action.”  Not all products are going to

cause problems in subsequent spray operations, even if some residue remains. “I think most farmers know that there are some products are not an issue, where a tank clean out problem has never been reported,” says Wolf. “Like glyphosate — it’s water-soluble, it washes out very readily with plain water and it tends to lose its effectiveness when diluted a reasonable amount. So even if you have some residue, and it gets diluted, it will be at a concentration where its effect is not noticeable.”  Other products, like Group 2s can be more problematic because they are highly effective at very low doses. “You can apply them at one thousandth of the recommended rate and they can cause damage to a very susceptible crop,” says Wolf. Group 2s are also absorbed by plants through the leaves and the soil, so they may have some degree of persistence in soil. “The persistence may be just days or weeks but if you get an inopportune rainfall you get essentially a double whammy in terms of the exposure of the crop,” says Wolf, “so that contributes to the potency.”

 RINSE IN THE FIELD FIRST 

Accurately measuring the amount of product necessary for the spray operation and accurately dispensing it in the field is important to minimize leftover spray solution. Once spraying is done, spray any remaining product out in the field. Over- spraying what has just been sprayed is fine because the registration process requires that the active ingredient in the herbicide be safe at twice the label rate, so it’s designed to accommodate overlap. Wolf suggests speeding up a little bit so as to under-apply the remaining product if there is any concern. Have clean water available in the field and add 10 times the sump’s remnant of clean water to the sprayer, circulate it and then spray that out (also in the field). Then repeat the process again. Having a clean water tank on the sprayer and a wash-down nozzle makes this job easier. You have now completed the first rinse operation before you fold up the booms and head back to wherever you plan to do a more thorough cleaning.

 CHECK THE SCREENS 

Now, take all the screens out of the sprayer and inspect them. If there is residue on them clean them thoroughly. There are screens in the nozzle bodies and this is often where residues accumulate and can reintroduce themselves into the spray liquid. There is also a main boom screen and various screens throughout the plumbing system of the sprayer all of these screens should be opened and observed and cleaned if there is any residue on them. Many of these screens are frequently overlooked. A wash bucket and scrubbing brush with clean water is handy for cleaning and rinsing screens. Check the spray boom end caps as well.

 USE THE APPROPRIATE CLEANING SOLUTION 

A good example of Group 2 injury of canola — multiple branching at the base of the plant.

When decontaminating after use of an oily (EC) formulation, the use of a wetting agent such as AgSurf will assist in removing oily residue that may trap SU herbicide on tank and hose material. Commercial tank cleaning products that contain ingredients for removing persistent deposits are available.

 WASH DOWN THE TANK WALLS 

Wash down the walls of the sprayer tank with a pressurized spray containing the ammonia solution and watch for any caking on the sprayer tank, and remove it using a direct, pressurized spray. Make sure that all parts of the

wall have been in contact with clean water. Use a wash-down nozzle to provide complete and vigorous coverage

of the interior tank surface. Afterwards spray the ammonia solution out also and dispose of it in a safe place.

The most effective use of any given volume of rinse water is to divide it equally across several repeat washes. Assuming a 10-gallon sump remainder, a single 600-gallon wash is as effective as two washes with 70 gallons each, and three with 30 gallons each. More wash cycles allow for less water in total.

 DON’T FORGET THE PUMPS AND PLUMBING 

Empty the sump as completely as possible by spraying it out. Any spray liquid or herbicide concentrate remaining in the sump area will be recirculated in the sprayer. The only way to remove any remaining herbicide is through dilution by repeatedly adding water, and each time draining the sump as much as possible.

Plumbing can also be a significant reservoir of herbicide residue. Pump clean water through the boom while ensuring that all return and agitation lines also receive clean water and all residue is flushed out. This may require opening and closing various valves several times and repeating the process with new batches of clean water.

 BE THOROUGH 

“It’s not as complicated as people may think,” says Wolf, “but you have to have your eyes open, you have to clean the right things and you have to make sure you observe if there is any residue left. If you are thorough you won’t have a problem.”

Angela Lovell writes from Manitou, Man.

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 Not all products cause problems, but some can even in tiny amounts 

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 DuPont Reformulates Its Group 2 Herbicides 

In 2006 DuPont re-formulated its line of Group 2 sulfonylurea (SU) herbicides with a proprietary soluble granule (SG) technology branded as Solumax soluble granules, which has, according to the company, improved plant uptake of the product as well as made life a little easier for farmers.

Original Dupont SU herbicides were dry flowable (DF) formulations using a clay-based carrier that, when mixed with water, didn’t entirely dissolve, instead forming a suspension in the sprayer tank. As a result, constant agitation was required to keep the product in suspension. Residue in the sprayer tank, nozzles, screens or other plumbing parts required more aggressive tank clean out procedures before moving into subsequent crops.

“Solumax as a carrier dissolves completely into a full solution, which makes clean out of the sprayer much easier. Solumax works similar to stirring a spoonful of sugar in a glass of water,” says Jon Gough, product manager for cereals at DuPont Canada. “When you stir it up and pick up that glass and look at it, you’ll see it’s completely transparent because it has gone into a complete solution.”

The new Solumax formulation is found in DuPont Barricade as well as Refine, Triton, Express®, Harmony and PrecisionPac brand herbicides. Du- Pont is the only company currently offering this technology in SU herbicides, and Gough says it provides additional benefits to farmers. “Weed control is more consistent because it gets into the plant quicker, which improves rain-fastness,” says Gough. “And equally important to growers is easier, more efficient sprayer tank clean out, so it really saves them time in the field.”

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 For more information on sprayer cleanout visit: 

University Of Missouri Extension Services. This link also has clean up recommendations for specific herbicide types. http://extension. missouri.edu/p/G4852

MAFRI Guide to Crop Protection –Page 14