How to Do a Soap Flush Test

Identifying an insect infestation in lawns can often become a time-consuming process. Because some of the most damaging pests rarely make an appearance above the soil, it can be challenging to detect an issue before your lawn experiences major symptoms. 

If you, like many homeowners, are seeking a method for identifying insects on your lawn, the soap flush test may be the best solution for detecting pests. Using this simple household item on your lawn, you can protect your turfgrass from the effects of many small yet harmful insects. 

Today, we’ll walk you through the basics of the soap flush test and how you can use it to identify insects in your yard.

What is a Soap Flush Test?

The soap flush test is a very simple yet effective method for spotting insects in lawns. As the name suggests, the soap flush test requires a mixture of dish detergent and water that can be used for monitoring both small and large areas of lawn. 

Once applied to grass, the soap will irritate any insects in the soil, forcing them to emerge to the surface. This method is effective for multiple types of insects ranging from chinch bugs to armyworms and mole crickets in the lawn.

How a Soap Flush Test Can Help You

Treating lawns for insects is often expensive, especially if you’re unsure whether or not pests are even in your lawn. Sometimes, damage from chinch bugs can closely resemble drought, for example. On top of that chinch bugs are really small, so they’re hard to see unless you’re actively looking for them in a specific area of the lawn.

A soap flush test will allow you to accurately conclude that there’s an infestation taking place instead of some other external stressor. Insect damage can also closely resemble damage from disease as well.

With the soap flush test, identifying insects is made possible before spending money on costly insecticides or other products.

Additionally, using the soap flush test can help you understand what type of insect you’ll be dealing with. This, in turn, allows you to buy the most effective insect control product for that particular infestation of insects on your lawn. 

“It’s one of my favorite tools and takes all the guesswork out.” – Gary Bradshaw, Homeowner

If you conduct a soap flush test, be sure to read our Insect Identification blog to help you identify which insects you might see. 

How to Do a Soap Flush Test

Performing the soap flush test is a fairly simple process that takes only 5–10 minutes. The most common techniques for applying the soap solution include using a watering can, a hose-end sprayer or a small container such as a bucket. 

The following steps include the instructions for preparation as well as the procedure for application.

Step 1: Prepare the Solution

Before preparing the solution, determine whether you’ll be monitoring a small or a large section of your lawn. For small areas (typically 1 sq. yd. of grass), add 2 ounces of liquid dish detergent to 1 gallon of water, then mix. Soaps such as Lemon Joy, Ultra Dawn and Ivory Clear are excellent options as they cause the least damage to turfgrass.

Homeowner Gary Bradshaw goes on to say, “Anything lemon-scented works better.”

If you plan on monitoring a large section of your lawn, prepare at least 1 gallon of a solution containing two parts water to one part liquid dish detergent. Note that soap solutions with higher rates than these can cause serious damage to turf. Applying the solution to a smaller area of the lawn allows the mixture to be more concentrated in that spot.

Step 2: Apply the Solution

After mixing the solution until soap suds appear, the next step is applying it to your lawn. As previously mentioned, you may use either a small container such as a watering can or a hose-end sprayer. Hose-end sprayers are the best option for covering a large area of lawn.

“I carry a piece of fine rope with me that’s pre-cut and a foot and a half across. Use the full gallon on that rope area, and then get on your hands and knees to look for them. Whatever is in there will come up. The insects need air and the soap mixture is an irritant. It may take minute or so. Wait on the bubbles,” says Bradshaw.

“Chinch bugs are really hard to see, so getting on your hands and knees will help you detect movement. Pour the solution around the border of the good grass. Don’t go back in the full brown grass that’s already damaged because insects won’t be as active in those areas.”

Once insects have damaged one area of the lawn, they generally move to other nearby areas to continue feeding on actively growing grass.

“Once the insects come up, they’ll stumble around and eventually die. It’s normal to see more than one type of insect. You may see beneficials as well. Pincher bugs/earwigs might come up too. They’re predators for chinch bugs. They don’t hurt the sod any.” 

Depending on the species and population, insects should emerge 5–10 minutes after application. Some insects, such as sod webworms, may not appear for 15 minutes. The following insects are the most common pests to identify with the soap flush test:

• Chinch bug 
• Mole cricket 
• Annual bluegrass weevil 
• Cutworm 
• Bluegrass billbug 
• Fall armyworm 
• Sod webworm 
• Grub worms

Pictured above from left to right: Chinch bugs, a mole cricket, a cutworm, a bluegrass billbug, a fall armyworm and a sod webworm.

How Do I Treat the Insects That Show Up After a Soap Flush?

Overall, this really depends on the type of insect that appears. Our Insect Identification Guide may be able to help you. You can also submit a specimen to your local university extension center for proper identification. Here are some of the best performing broad-spectrum insect control products.

In summary, the soap flush test is an effective method for homeowners looking to identify insects in their lawns. 

Whether you’re looking for Florida insect identification or pest identification in colder climates, this technique allows you to spot an insect infestation before it becomes a significant problem.