How to spray your lawn. When you buy a product to treat your lawn either for weeds, pest or disease the labels can be confusing. Often, the label tells you to apply a concentrate rate of product within a range which can vary significantly. For example, it could be 200ml to 400ml. It will then say to cover 100m². Sometimes it will just say to cover a certain area only, or, it may also say in an amount of water which may also vary between 10L to 20L water.
The question is, how do you decipher this often-confusing information. Before you start, there are a number of things to understand about Pesticide controls and how they work on application.
Age and size of the Weeds – you need to consider the size of the weeds. Are they just germinating, if so, you can use the lesser rate unless it stipulates a set rate so refer to label. If the rate has a min and max use the higher rate for more mature weeds.
Species of Insects – It is important to understand the insect you are wanting to treat. Are they below the ground, such as black beetle or above the surface like Army Worm. This is important because some products work on contact at the surface, while others need to be watered into the soil and thatch where the pest is doing damage, Additionally, some may be systemic, which means the plant needs to absorb the product so when the pest chews or sucks on the roots or leaves it then ingests the product and dies. Finally, do you need to repeat the process in 7-10 days to break up the lifecycle of the pest.
Disease – Most fungicides need to be applied with a heavy rate of water to saturate the spores. Often there is the addition of a wetting agent and the requirement to water the product in. This is because most fungus are in the soil, so wetting agent helps to penetrate our hydrophobic soil and the water flushes it through.
So, once you have read the label and know what rate of concentrate you need and understood the Pest you are treating, it is time to work out how much water and product you need to treat an area, for example 100m².
Basically, they are providing you with a rate of concentrate to be effective. The question of how much water to apply is a valid question, but realise the amount of water required depends on your method of application, as the water is only a carrier to help get the concentrate over a given area. It would be almost impossible to apply a concentrate of 400ml over 100m², so here’s what you do.
- Fill up your sprayer with water. We are going to use as an example the standard 5 ltr sprayer
2. Now go to your driveway and measure out an area of 10m². Spray that area with clean water, you will see how accurate you are by the water hitting your driveway. Use a repetitive, even motion.
3. Once you have covered the 10m² area, get a measuring jug and refill your spray bottle and record how much water you have used to cover 10m². Let’s say you used 800ml over 10m². All you do now is multiply 800ml x 10 (10x10m² = 100m²) which is 8000ml, or 8 litres.
4. So, to cover 100m² you will need to use 8 litres of water. Depending on the rate you want to use of concentrate you can simply divide per litre. Our example is 400ml of concentrate. You divide it in half (as you only have a 5ltr sprayer), so if you need 8 litres, I would put 200ml concentrate into 4 litres, spray half or 50m² and then repeat on the other half and job done, completely accurate.
Example 1. Nutgrass has a very shiny, slippery leaf and stem and the product needs to be absorbed through the leaf, not the roots. This particular pest requires the addition of a sticking agent, generally a wetting agent works very well and the amount is often stated on the label. Being mindful of the slippery leaf then tells us not to use too much water as the carrier as it will cause the product to run off the leaf so you should use the minimum amount of water and apply it in a fine mist.
Example 2 -With a fungus such as “Brown Patch” you want to apply a heavy rate to gain good coverage and saturate the soil to treat all spores, then water in. It will state on the label how much irrigation to apply to get the product to percolate to where it needs to be. Generally to get products into the soil you want to use the maximum amount of water with heavier droplets.