Should You Water Your Lawn After Applying Fungicide?

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A slight sign of lawn fungal infestation, whether highly visible slimes, rings, threads, spots, or even a tiny patch of brown dead-looking grass, is enough to have you rushing to get fungicide.

While this treatment is effective, it requires proper application bringing us to ask, should you water your lawn after applying fungicide?

You can water your lawn after applying systemic fungicide to prevent root rot. However, don’t water your lawn for a minimum of 24 hours if you apply contact fungicide to avoid washing away the treatment’s protective layer from the grass’ leaves.

It’s paramount to read the manufacturer’s instructions before using a fungicide to ensure you use it appropriately.

This post will cover using fungicide correctly to guarantee its effectiveness in killing fungi.

Should You Water Your Lawn After Applying Fungicide?

should you water your lawn after applying fungicide

Some fungicides need to be watered in, while others don’t, so the answer to this question will depend on whether you used systemic or contact fungicide on your lawn. Contact fungicides stay on the leaf surface to give a protective covering, thus keeping fungal infection at bay.

You shouldn’t water in contact fungicides because that will wash away the protective layer, rendering it useless.

On the other hand, systemic fungicides are absorbed into the stems, leaves, and roots to fight the fungal infection from the inside out.

Systemic fungicides should be watered in after application, but don’t overwater your lawn to avoid taking the chemical too deep into the soil where roots can’t access.

Read more: Does soapy water kill lawn fungus

Systemic Fungicides

These anti-fungal chemicals move internally in the grass after being absorbed into the roots, leaves, and stems. A systemic fungicide suppresses the fungal infection and facilitates new healthy growth.

They can work as a cure for an existing fungal infection or prevent fungal infections. In addition, they last longer than contact fungicides and need to be watered in to be effective.

Unlike contact fungicides, rainfall isn’t a big issue for systemic fungicides as it can help spread the chemicals. Therefore, you don’t need to reapply systemic fungicide if it rains, although too much rain can wash away the chemicals before being absorbed by the grass.

It’s best to apply systemic fungicides after a good rainfall.

Contact Fungicides

Unlike systemic fungicides, contact fungicides are not absorbed into the grass but rather create a protective layer on the surface. Since they form a protective barrier, these chemicals are excellent as a protective measure but less effective in curing fungal infections.

Watering your grass after applying contact fungicide is a no-no because the water will wash away the chemicals. Moreover, rain isn’t good for contact fungicides, and you will need to reapply if it rains after application.

In addition, you should limit your footprint on the lawn to avoid removing the fungicide. These fungicides don’t last long (a few days to a week), so you need to reapply often.

Contact fungicides are excellent for diseases like brown patch disease in Bermuda and St. Augustine grass, among other grasses.

Can You Apply Fungicide On Wet Grass?

You can apply certain fungicides on wet grass, including Fame Granular Fungicide. Dew or water improves these treatment’s contact action making them more effective.

Therefore, water the lawn lightly before application or do it after a light shower to ensure the chemicals stick on the blades’ surface. Your grass doesn’t have to be wet when applying systemic fungicides because they are sprayed.

However, remember wet grass offer a conducive environment for the spread and growth of fungus on your lawn.

Should You Water Lawn After Applying Scotts Fungicide?

You shouldn’t water your lawn for about 48 hours after applying Scotts Disease Ex to avoid washing away the chemical. This fungicide will start acting 24 hours after application and can control diseases for up to a month if used in a systematic manner.

It can be used in a curative and preventative way, making it a pretty useful product. It effectively fights lawn fungus, Pythium, yellow patch, Powdery Mildew, brown patch, red thread, stripe rust, Typhula & Southern Blight, Necrotic Ring Spot, and Pink Patch, among other lawn diseases.

To be effective, you need to know the correct procedure for using Scotts Disease EX.

How Long Does Fungicide Need To Be On Before Rain?

The issue of rain affecting the effectiveness of fungicide depends on the type of fungicide used and the rain intensity. Your contact fungicide will be rendered useless if it rains within an hour after application, and its effectiveness is reduced if it rains within a day following its application.

On the other hand, a majority of systemic fungicides become rainfast after a couple of hours. However, you will need to give some fungicides up to 24 hours to be fully absorbed by the grass.

Light rain can help systemic fungicide penetrate the soil, allowing the roots to absorb the chemicals. However, heavy rains can wash away the chemicals before absorption occurs.

Ideally, 24 hours without rain is sufficient for contact fungicide to protect your grass against fungal diseases, with its effectiveness increasing as the number of hours without rain increases. However, anything below 24 hours without rain makes contact fungicide less effective.

Consider using the highest recommended quantities of fungicide if you suspect rainfall. While some of the chemicals will wash away in the rain, some will also remain.

Reapply Fungicide After It Rains

You will need to reapply if it suddenly rains after applying contact fungicide or before the systematic fungicide is absorbed. This applies to rainfall that occurs within 24 hours after applying fungicide on your lawn.

The rain will wash away the chemicals in contact fungicide, preventing it from creating a protective layer against fungal diseases. You are better off applying fungicide after the rains.

Final Remarks

Finding fungus on your lawn is quite disappointing, but luckily, this is a problem you can solve using the right fungicide.

So, should you water your lawn after applying fungicide?

Don’t water your lawn for a minimum of 24 hours if you apply contact fungicide to avoid washing away the treatment’s protective layer from the grass’ leaves. However, you can water your lawn after applying systemic fungicide to prevent root rot. 

Whether you use contact or systemic fungicide, follow the manufacturer’s recommendations.


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