Cat Grass Bugs: Are They a Danger and How to Get Rid of Them

cat and kitten eating grass

Eew! Bugs, flies, and other creepy crawlies on your cat grass? Try these proven solutions:

  1. Be super safe—Throw away the cat grass and start again.

  2. Use a forceful stream of water to clean the bugs off the blades.

  3. Do not overwater—overwatering causes decay: food for bugs.

  4. Keep changing the locations of the plant containers.

  5. For outside cat grass, introduce natural predators.

Your cat grass has bugs or flies.

This can be the case whether your cat grass is grown in a container inside or outside your home, or directly in the dirt outside.

Fortunately, my solutions can put an end to those creepy crawlers…or fliers.


Most people recommend not growing cat grass outside. 

If it is grown outside, pesticides or herbicides which are dangerous to cats could get onto your cat grass.  

Even if you don’t use chemicals dangerous to cats, your neighbor or garden service could— without you knowing.

Most people grow their cat grass inside just to be safe.

Also never use pesticides or herbicides to kill bugs in cat grass, as they will probably harm your cat.

1. Is it ok if my cat eats the bugs in the cat grass?

In general, the risk of cat health issues from eating bugs is small.

If there are any side effects, they are usually vomiting or diarrhea which should stop in a day or two.

Bugs in contact with pesticides

Usually, the bodies of these bugs contain a very low amount of toxin

As a result, you will most likely not see any negative side effects in your pet.   

Bugs with internal parasites

Again, the risk is very low and cases are “few and far between”.

Bugs to watch out for

There are a few common bugs which cats should not eat. However, these are usually not the ones in the  cat grass.



The chemical luciferin is part of the complex process that makes fireflies glow.

Some fireflies have a related toxin named lucibufagin. This chemical toxin can kill animals, including your cat.

Monarch caterpillars

monarch caterpillar

This pre-butterfly stage is poisonous to your cat. 

Left untreated, eating a monarch caterpillar could cause your cat to die.

Usually, cats don’t eat monarch caterpillars because they taste extremely bitter.

Cockroaches, beetles, crickets

These bugs can have parasites. So, eating one can give your cat stomach worms

In any case, concerned that your cat has eaten bugs in their grass which might be poisonous (or something else which might do them serious harm)?

The ASPCA Animal Poison Control Center (APCC) is on hand 24/7/365 for any poison-related emergency concerning an animal.

Their number is (888) 426-4435. 

You may have to pay a consultation fee.

2. How do I get rid of those green bugs in the cat grass?


The green bugs in the cat’s grass  are most probably aphids. Aphids can also be peach, black or red colored. 

The sticky residue that aphids leave while feeding is attractive to ants. So, soon, you may have two types of bugs in the grass, instead of just one.


Insecticidal soap is one option. However, it is not recommended as insecticides and kitties do not mix. 

A natural, cat-friendly solution is to wash them off the cat grass with a strong spray of water.

For outside cat grass bug problems, you can increase aphid-eating predators in your garden such as lady beetles (aka ladybird beetles or ladybugs).

3. It looks like I have flies in my cat grass. What should I do?

fungus gnat

They may look like flies but the bugs are most likely fungus gnats.

Fungus gnats like to eat rotting organic matter. When the top one inch (2.5 cm) of the cat grass soil is too wet too often, things rot, exactly what the fungus gnats like.

These bugs did not come in the grass seed or in its package.

Most likely, they were in the soil or potting medium you recycled from a different plant or took from the outside in.  


You need to be careful when using soil from outside, and make sure it doesn’t contain pesticides and herbicides as they are dangerous for cats.


Cut down on the water you are giving your cat grass. As the soil dries out and stays drier, the food will disappear, and so will the fungus gnats.

You may wish to throw away this container of cat grass and start again. 

If you begin again, make sure your soil is bug-free:

  • Use new soil or potting medium. 
  • Alternatively, bake recycled soil at 250F (120 C) for roughly an hour. 

To prevent damage to your metal roasting pan while baking soil, line it with aluminum foil. You can also use an unlined glass casserole dish.

4. My cat grass blades have holes in them.


Ah, that is the work of armyworms

Both the darker green adults (with a pink underneath and a light line along the side) and pale green larvae leave patterns of single holes or clumps of holes as they munch on the blades.

Skeletonized blades are another sign. 

Do you see cottony or fuzzy clumps? These are the armyworm egg clusters.


The best advice is to introduce their natural enemies.

Since these include several types of fungi, you may just want to throw away the cat grass container with these bugs and try again.

5. The blades of the cat grass are holey or gone, AND there are slimy trails on the dirt.


Your culprits are slugs.

Night and damp weather are the perfect feeding conditions for slugs.


Handpick the slugs off your cat grass.

Use a beer trap.

Here’s how I set up beer traps:  

Step 1:

I filled several empty beer bottles with several inches (cm) of beer.

Step 2:

Then I dug angled holes in the ground and laid the bottles on their sides in these holes so that just their tops were lying on the surface.

Step 3:

The next morning, I threw the slug-filled bottles away. You could also dump out the drowned slugs and leave them as a treat for the birds.

6. I see that white flies leave the cat grass whenever my cat moves the blades.


This description fits whitefly


Unfortunately, whitefly is best controlled with chemicals.

The Cooperative Extension Service in your state can advise you about which pesticides are allowed in your area and are the least problematic for your pet. Be very careful with this one to ensure you do not use a pesticide or herbicide that can hurt your cat.

Cooperative Extension Service

The Backstory

Farmers need lots of advice about a wide variety of agricultural and farming issues. 

The best advice would come from a local expert, someone who understood how their general knowledge worked best for the local area.

So, in 1914, the U.S. Department of Agriculture created a system of ‘extension’ services by asking designated land-grant universities across America to partner with them.  


At the moment, each state has an extension service whose job is to answer local questions about gardening and farming…including bugs in cat grass.

You can find the Cooperative Extension Service in your state here.

7. My bugs are actually worms and beetles.


Wireworms are ¼ – ¾ inch long worms when they are young (0.6 – 1.9 cm).

adult wireworm lifecycle beetle

The worms are yellow-brown and rather thin. Their skin is shiny.

Adult wireworms are long, red-brown, ⅓ inch long (0.84 cm) hard-shelled beetles known as click beetles.  


One method is to plant your cat grass in different locations each time. This makes it more difficult for these bugs to find it. 

The best thing though is to plant it in a separate pot in your home, away from any other plants you may be growing.

You can also ask for advice from your local Cooperative Extension Service.

8. There are crawling bugs, black soot on the leaves, and egg clusters.


Sounds like mealybugs


It is not recommended to use insecticides to control this pest.

One solution is a forcible stream of water with a high pressure (if possible). Spray it directly on the mealybugs.

If your cat grass is outside, try introducing more mealybug predators. These include spiders, lady beetles (ladybugs), minute pirate bugs, and green/brown lacewings.

Otherwise, throw away your buggy cat grass, and try again.

P.S.  …

My grandson has three (rapidly growing) lizards. Lizards eat most of the bugs that can be found in cat grass.

And they like to eat LOTS of those bugs at every meal.

(Don’t ask me how I know!)

So if you have a neighbor with lizards, you could offer to have them over to your ‘restaurant’ for a meal or two…

Writer: Lisa Aharon

lisa aharon