One size doesn’t fit all
Scotty’s Tips - One size doesn’t fit all!
By Scott Mathew, Senior Solutions Development Lead @knat71
A recent trip to the Goulburn Valley to present at an application workshop for stone fruit growers reminded me of the importance of understanding crop protection product and water application rates. It’s a clear case of ‘one size does not fit all’ and in the same way as our kids outgrow their clothing, water and crop protection product rates per hectare need to be adjusted as the season progresses to maintain good coverage.
Many product labels no longer have a rate per hectare. Instead you’ll see instructions similar to the example below.
Blossom Blight (Monilinia laxa),
Brown Rot (Monilinia fructicola)
Apply by dilute or concentrate spraying equipment.
Apply the same total amount of product to the target crop whether applying this product by dilute or concentrate spraying methods.
Dilute spraying is when the sprayer is set up to apply a volume of water to the point of run-off. The point of run-off is when enough water is applied to wet the plant so that some spray droplets join and run off the targeted area, whether that is the foliage or fruit (just because you have run-off on the outside of the canopy, that does not indicate a dilute application volume). Thorough canopy coverage is important, as is avoiding any excessive run-off. Once the dilute spraying water volume has been determined, add the amount of product specified in the Direction for Use table for each 100 L of water.
As the crop canopy grows you increase the water volume per hectare to maintain good point of run-off coverage. As a consequence, the product rate per hectare increases in proportion.
Concentrate spraying is any situation where you are spraying your crop with a water volume that is less than the ‘point of run-off’ or dilute spraying rate. If you choose to do this, you’ll need a sprayer that is well designed and set up for the purpose of concentrate spraying. To calculate your product rate, you will also need to know what the dilute spraying water volume is for your canopy. Remembering too, that the dilute spraying volume changes as the season progresses and the crop canopy grows.
The mixing rate for concentrate spraying can be calculated as follows:
- Dilute spray volume as determined by point of run-off. As an example, if you are spraying traditional open-vase trellis stone fruit in the Goulburn Valley, your dilute application rate may be 2000 L/ha.
- Your chosen concentrate spray volume is 1000 L/ha.
- The concentration factor in this case would be two (i.e. 2000 L ÷ 1000 L = 2).
- If the dilute label rate for CHORUS® for example is 40 g per 100 L, then the concentrate rate becomes 2 x 40 g, or 80 g per 100 L for concentrate spraying.
- The rate/ha of product applied would be: 80 g x 10 (as 1000 L is the concentrate water volume/ha) = 800 g/ha of CHORUS.
The key point is, regardless of which water volume method you choose, whether dilute or concentrate, you still apply the same product amount per hectare and the product rate per hectare may need to be changed as the crop grows. For further information on concentrate spraying, growers are advised to consult relevant industry guidelines or undertake appropriate competency training. Finally, always remember to seek professional advice for your specific situation.