Spraying insecticides or fungicides upwards with a knapsack sprayer

This video will show you how to spray pesticide upward but using water to practice with.

You will need:

• your pesticide label,
• your knapsack sprayer,
• clean water

and 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, your
• your nozzle flow rate and the
• knapsack sprayer pressure or pumping rate.

In this demonstration, the label advises us to use 75 ml of contact insecticide in 400 L of water to the hectare of treated area or 400 ml to every 10 square meters of treated area, to control White fly in tomatoes.

The label advises the use of a hollow cone nozzle to spray ‘Fine’ 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 sprayer will be pressurised to 1.6 bar.

The foliage of this section of the tomato row is 10 meters long and 1 meter wide, which is a total of 10 square meters.

To apply 400 ml to this area, we have calculated that the operator will need to spray for 40 seconds, and so should spray each side of the row for 20 seconds each.

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.

The operator will be spraying upwards and laterally with the nozzle 50cm from the foliage. It is really important that you wear the correct PPE when spraying upwards.

This is because in order to spray the tops of taller trees, you will need to angle the spray projection steeply upwards. Whilst some spray will be projected safely upwards for up to a metre, some drops will fall back down.

Wear a coverall with a hood and make sure that the hood is pulled up and over the head.

The sleeves of your gloves should be on the outside of your coverall sleeves or you could use tape to close the gap between sleeve and glove.

When practicing to spray upwards and laterally with water, start at the top of the foliage and move the nozzle down……, then move the nozzle across half a metre and spray up, ……... then move the nozzle across half a metre and spray down. For higher foliage you may need to fix an extension to your lance. Extensions enable the nozzle to be positioned closer to the spray targets in the highest points of the canopy.

Keep the nozzle about 50 cms away from the outer leaves of the canopy to achieve the full width of the swath - in this case half a metre.

The intensity of small, fine sized drops generated by hollow cone nozzles and the angles of their projection

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

Monitor your spraying pressure and keep your spraying speed constant. Constantly check that your nozzle is producing the right spray pattern and drop size.

Be careful neither to spray the ground nor to spray over the top of the row as this will waste your pesticide and be a risk to the environment or anyone near you.

Where you are spraying crops in a rows, like these, spray first one side of the crop in the row and then go to the other side of the row and continue spraying.

Check that each leaf is sprayed and has a cover of drops.Check that spray is reaching all the leaves within the canopy; those that are lower down as well as those at the top; those on the outer sides as well as those within.

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 insecticide needs to 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 where spraying must re-start with the next load.

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