Fungicide Application – When should fungicide be applied in Lawn?

A fungi-infested lawn isn’t a beautiful sight to behold. The affected parts are brown, leaving unsightly patches on the green field. When you manicure and tidy your lawn, you can reduce the likelihood of fungal invasion. 

Even if the inevitable happens, you should always arm yourself with antifungals as a last resort. Sprays, powders, and granules are among the most common forms of fungicides, which can be either systemic or contact types. 

Trimming to not less than a third of the length of the grass blades, increasing the depth of watering and decreasing its frequency, and ensuring nutrient sufficiency boost the plant’s immunity against fungal infections. 

While fungicides eliminate the cause, the symptoms prevail.  Maintaining a healthy lawn is an enormous task that many homeowners may not be able to allocate adequate time for. 

The easiest and most obvious alternative is to shop for an effective fungicides for lawns, but this isn’t always the most feasible option as we are going to find out. Stay tuned as we take you through the nuggets of valuable tips to care for your lawn.

Do You Water After Applying Fungicide?

While fungicides come in different forms, they loosely belong to two groups: contact and systemic types. Your choice of either group determines whether you should water after applying it. 

Contact Residues

When a spore or a hypha comes into contact with the contact substances on the surface, it dies. If you choose contact fungicide, wait for between a few days and a week after applying the type to water your lawn. 

Then, you can reapply it and wait for the time interval. If you water your lawn immediately after applying the contact fungicide, you’ll wash off the protective antifungal layer on the leaves. Make sure you reapply contact fungicides after rain to replace the leached materials. 

Systemic Substances

On the other hand, systemic fungicides work like translocated herbicides. The roots absorb the active compounds and they translocate across the whole plant through phloem and xylem because of water action. 

When the active compounds encounter a hypha or a spore that has penetrated the plant’s interior, they eliminate it. Thus, you need to water your lawn before, during or after applying systemic fungicides. 

Contact and systemic residues that remain on the surface are more susceptible to leaching than systemic materials that the plant has absorbed and redistributed within its body.

How Long Does Fungicide Need to Be on Before Rain?

The answer to this question boils down to three things: adsorption, weathering agents (sunlight, microbes, temperature, and water or moisture) and redistribution. 


Rain washes off the active materials on the plant’s or leaf’s surface. The active residues adsorb on the plant’s surface, or the plant absorbs and redistributes them across its entire system.

But adsorption power (the strength with which the residues stick on the surface) differ between fungicides. The greater the adsorption power, the less the susceptibility to leaching.

Adequate evidence indicates that fungicide residues differ in the resistance to removal by rainfall on the plant’s surface. 

Herbicides that take less time to get adsorbed on the surface or get absorbed into the system are readier to rainfall than those that take longer to infiltrate the plant. 

Weathering Agents

Besides, ultraviolet radiation from sunlight, a microbe, or heat contributes to the degradation of the active residues over time, reducing their effectiveness against the malicious spores or hyphae. 

Therefore, newer fungicide residues are more robust than their older counterparts. Morning dew, rainfall, or irrigants redistribute the active substances over the surface, decreasing the effectiveness, although the redistribution rates differ between the fungicides. 


Redistribution isn’t a bad thing in and on itself. However, when rainfall amounts exceed two inches immediately after you apply the fungicide, or exceed one-inch after a week of application, you should reapply the protective layer of residues.

When Can I Mow After Applying Fungicide?

You need to strike the right balance between mowing and fungicide application. If you get mowing right, you can prevent fungal disease infestation and fungicide application in the first place. For many homeowners, it’s a massive challenge to keep your lawn neat and healthy all the time. 

And so, most resort to the easiest option: fungicide application. There isn’t much time to juggle between work, leisure and lawn care, fungi and other scourges will have invaded your turf the next time you take care of your lawn or garden. The best practice is to cut your lawn grass to a third of its height (not less than three inches). 

But it doesn’t just stop at that. Avoid depending on fungicides to eliminate your nemesis because when they evolve to be resistant, no amount of anti-fungal chemical will work against them. When push comes to shove, you may need to switch between types that differ in their actions. 

Avoid frequent application as much as you can. Experts recommend applying the chemical every fortnight or two. But in case you are unsure, you can rely on local forecasting systems to determine the right frequency for your region, weather, or soil type. 


As they say, prevention is better than cure. However, because of busy lifestyles that involve juggling between work, leisure, and lawn care, fungi, weeds, pests, and other troublemakers capitalize on the period when you are focused on doing things other than caring for your lawn. 

And so, for many, it can be hectic to think about regularly maintaining the health and tidiness of the members of your yard. The surging popularity of fungicides and herbicides isn’t a surprise given this trend. Yet, you should approach the use of chemicals with a grain of salt. 

Fungi can develop resistance, and that can spell disaster for your lawn. The key takeaway is to rotate fungicide use. Know the best frequency to apply fungicide. If you are passionate homeowner, why not hire someone to regularly maintain your lawn? The benefits may outweigh the costs.

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