Whiteflies on Cannabis Plants: How to Prevent and Destroy!

Whiteflies those sap-sucking annoying insects that can ruin your outdoor grow. 

Most growers located in the Southern Coastal states know that these flies last all year long, and they are a common pest to the outdoor cannabis grower. 

Not only do they affect your overall yield, the leaves get all sticky and sometimes black mold can grow which is really bad.

In this post you learn most of all how to kill whiteflies also what to look out for, what causes them.

We also give you a some insight of actually what they are so you can prevent your marijuana garden being destroyed by these tiny moths

Signs of Whiteflies

Here are some of the signs you can is plants may have some white flies. 

Stunted growth you notice your plants not growing as tall as they should be

Yellow leaves, you know your nutrients are o point check under those leaves!

Sticky Coating on leaves ( honeydew from the flies)

Black sooty mold on the leaves of your marijuana plants

White dots in a circular spots on the underside of leaves ( these are eggs and larvae)

Clusters of white dots found underneath cannabis leaves 

Greenhouses are a known hang out.

Underneath the leaf hiding!

What causes whiteflies

Some of the main things that contribute to a whitefly outbreak are:

  • Common houseplants can have some hanging around.
  • Soil purchased in bags can also be infested.
  • Outside Plants when you bring plants in from outside. 
  • Other plants in the area of grow have the infestation when growing outdoors.

What are whiteflies 

Whiteflies are related to aphids and mealybugs and they are sap sucking insects.

Just like with aphids,  whiteflies also secrete honeydew so leaves may be sticky to the touch, or even covered in a black soot mold.

They are around 1/16 inch big and look like tiny moths and are found in clusters under leaves.

These types of flies are active during the day, unlike other insects, which is good so you can see them in action and eliminate them. 

Whiteflies young nymphs can last winter and in the spring lay up to 200- 300 eggs on the underside of leaves.

Once the eggs hatch in 5-10 days it can resemble mealybugs on leaves.

The total time for the evolution of the white fly is 25 days from egg to adults. The adults can live about another 1- 2 months .

Normally growing cannabis you don’t leave plants out in winter. But there are other plants in your area that can possibly harbor the elusive whiteflies.

So if your growing outdoor be careful of your surroundings and check plants around your grow so they do not decide to migrate over to your plants

How to Prevent 

Here are some simple ways to prevent white flies form invading your cannabis garden:


Check plants surrounding grow when growing outdoors


Look under your leaves on your plants to make sure none are hiding.


Spray a preventative during the veg stage.


Have yellow sticky tape around plants.


Have screens on greenhouse windows if possible.

Whiteflies during flowering

Any type of insects or bugs that you have during the flowering cycle.

When your cannabis plants are in the phase of growing buds or have established colas, it’s really hard to get rid of them.

Spraying your plants in flower is a risky bet because you could have possible mold growing afterwards.

This will happen if the plants do not get enough airflow for them to dry properly especially with colas.

You will also risk your trichome development on your cannabis plants .

Here are some solutions that may help but it’s not guaranteed use with caution.

Know there’s always a risk and this advice is not responsible for anything that happens afterwards. 

Spraying your cannabis plants with insecticidal soap a diluted amount or with neem oil. 

Do not spray in two consecutive days allow for the soap or oil to work on the eggs and nymphs.

If the flies are gone from what you can tell then, 

During Harvest you can wash your buds trimmed of big leaves still on the branch in a water bath with hydrogen peroxide.

Then rinse and hang dry your buds with ample airflow with the help of fans once dried to continue the drying and curing process .

Use 5 gallons of water for the bath with about 5-8 oz of hydrogen peroxide. (This will also remove powdery mildew and mold from your buds). Then have another bin full of clean rinse water.

Use the spray method with caution in flower.

White flies in a circular pattern.

How to Kill

Here are some of the best ways to kill white flies on cannabis plants all ways are natural:

Sticky yellow trap paper is a great first step in preventing whiteflies from infesting your garden.

Also they’re really great at trapping the females when they’re flying around trying to lay their eggs on your cannabis plants leaves.

White flies are attracted to the yellow color and this also works for other insects in the garden so it has a multi-purpose use. 

Ladybugs Love to eat whiteflies and they are easily available on Amazon.

It’s really inexpensive way for you can help eliminate not only white flies in the grow but many other pests as well.

You can also use ladybugs indoors if you have a closed grow room or grow tent that is closed off as well but be careful not to let them out into other areas of your house or grow area. 

Ladybugs are also great for outdoors you can actually just place them on your plants and they’ll just hang out there for a while and Munch away. 

Dragonflies are a natural predator to the white fly and if it the season they should be around your plants if you have any pests.

If you notice take a second look to see if there are any whitelies on your outdoor marijuana plants.

Insecticidal Soap is a great way to get rid of whiteflies on your cannabis plants.

Made with al natural ingredient of potassium salts a fatty acids from plants this natural insecticide will kill on contact .

Works on other insects as well always great to have in your arsenal against almost any invader in your cannabis garden.

Spray on the underside of your eaves to kill any whiteflies you may have without harming your plant.

Neem Oil is another multi-purpose use solution that can get rid of whiteflies and other pests in your garden.

This concentrate is made from the seed of a neem tree.

There are many different types of neem oil out there some are ready to go others you can buy the concentrate.

It’s usually always organic and mix about 1 oz per gallon of water .

Neem oil will not harm  pets or beneficial bacteria in your soil. It;s also safe for all fruits and vegetables.

Safer Soap Is another type of insecticidal soap also made from the fatty acids from plants and potassium sulfate.

This may come in a concentrated form and you can use it by ( mixing 2.5 ounces per gallon ).

Then spray on the underside of your plants leaves for best results you may need to apply it twice. 

Botanigard is the Cadillac in insect control, works on a lot of pests including the whiteflies. 

This product is approved by Health Canada for the licence producers to be used on their medical cannabis crops and commercial grown as well.

Botanigard is expensive but it does the job. This is insecticide contains powerful combination of pyrethrins along with Beauveria bassiana Strain GHA.

You are able to use Botanigard with other insecticides and fungicides without issue.

Final thoughts

Whiteflies can be a nuisance to your cannabis garden.

If you can spot them soon enough and take some preventive measures such as using a yellow sticky tape and spraying with insecticidal soap during the vegetative cycle.

Then your plants will not suffer a reduced yield at harvest. 

If you have an infestation of white flies that it’s getting out of control and impacting many other plants.

I recommend using botanigard it is expensive but it does work.  

Remember to always check the underside of your leaves for any white dots and use a portable microscope to see what those spots are if it’s a mold or whitefly.

Have you had whiteflies infest your grow?

What did you do to prevent them?

Let me know in the comments

Keep growing my friend

Photo Credits: Flickr: gbohne, Katja Schulz

1 thought on “Whiteflies on Cannabis Plants: How to Prevent and Destroy!”

  1. I wish I had read this earlier, but now knowing how to prevent them next season is good knowledge .
    I will try Botanigard , maybe save my crop. I’m in mid flower now.


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