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Spraying insecticides or fungicides laterally with a knapsack sprayer


This video will show you how to laterally spray a pesticide, using water. Click the play button to view the video now or click on the script tab to view the storyboard. To view the video off-line, click the link from the 'download' tab.


This video will show you how to spray pesticide laterally to the side of a target bush or tree but using water to practice with.






You will need:

  • a small area of dry concrete
  • your pesticide label
  • a knapsack sprayer and its nozzle
  • clean water
  • canes or sticks



and the personal protective equipment as directed by your pesticide label.






From the pesticide label you will also know:

  • the amount of pesticide to be applied
  • the water volume rate to use and
  • the type of nozzle advised.



You will have used some of this information to find out the size of nozzle you need and so will now also know your:

  • row or swath width or the width of the canopy that you will be spraying
  • your comfortable spraying speed
  • the nozzle flow rate and the
  • pressure of the knapsack sprayer.



In this demonstration, the label advises us to use 75 ml of a contact insecticide in 800 litres of water to the hectare, or 80 ml for every square metre, of treated area, to control our example pest in coffee.





These coffee trees cover 2 square metres of ground so each tree will need to be treated with 160 ml of spray; 80 ml being applied from each side of the row.





We have elected to use a hollow cone nozzle to spray medium sized drops.





We have calculated that the nozzle size we need has a flow rate of 0.6 litres/minute [or 10 ml/second].





The swath width produced by the nozzle is 0.5 metres and the knapsack pressure will be 1.6 bar. Our operator will be spraying laterally with the nozzle 50 cm from the foliage and





the knapsack pressure will 1.6 bar.





Our operator will be spraying laterally with the nozzle 50 cm from the foliage.





When practicing spraying, only use clean water.





And wear your PPE so that you get used to wearing it and can adjust it so that you are comfortable. Some pesticide labels will permit the use of long sleeved shirt and trousers as dedicated PPE; a better option is to wear a coverall. (Always wash PPE separately).





This knapsack has already been cleaned, checked, and calibrated.. If you are not familiar with how to do this, please have a look at our separate videos.





When practicing spraying bushes using water, start at the top of the bush and move the nozzle carefully from one side to the other. Keep the nozzle about 50 cm away from the outer leaves of the canopy to achieve the full width of the swath - in this case half a meter.





The size of these drops and the angles of their projection ensure that





the leaves at the front of the canopy, the concealed leaves within and the stems are all sprayed.





When you have sprayed the full width of the bush, move the nozzle down the width of the swath spray back across the bush. Be careful neither to spray the ground nor to spray over the top of the bush as this will waste your product and be a risk to the environment or anyone near you.





When you have sprayed the one side of all the crop in a row, go to the other side of the row and continue spraying. Monitor your spraying pressure and keep your spraying speed constant. Constantly check that your nozzle is producing the right spray pattern and drop size.





From time to time stop and check to see if the drops have been evenly applied by looking at the leaves at the top and bottom of the bush, at the sides and inside the leaf canopy.





If some of the leaves have received too much pesticide – like this one where the drops have accumulated and dripped off onto the ground, then the nozzle was being moved too slowly.





Practice again until you have the best deposits on the leaves. This contact acting insecticides should be sprayed using smaller drops to produce an almost complete cover of drops over every leaf. All contact pesticides will only control the pest where the sprayed drop has made direct contact with the pest, so check that every leaf and stem has a cover of small drops over the entire target surface.





When air is coming out of the nozzle and the spray liquid is all used, place a stick at this point to mark the point where spraying must start again with the next load.





Leave a small unsprayed area to be sprayed later with the water used to clean the inside of the sprayer.