Thrips on a Cannabis Plant

There are many bugs that can invade your grow room. Being able to identify which bug is eating your plants is crucial to treating the problem correctly. Thrips on a cannabis plant is common, maybe even more common than spider mites.

Prevention is better than cure in all pest and bug related issues. Before you treat any bug issues, you must find the source first. Find out where the bugs are coming from, stop them from entering again. Then treat the plants however you need to.

If you have found thrips on your cannabis plants, and you need help to get rid of them, then feel free to ask for help in our cannabis growers forum

What are Thrips?

Thrips are tiny insects, that are very hard to spot, especially when they are young. Like most bugs, it is always better to look for the symptoms of them being there, rather than looking for the bugs themselves.

signs of thrips on a cannabis plant

When thrips first get into your grow room, a female will tear slits in the leaves, and lay an egg into it. You need to look out for silver, dry spit looking patches. Along with these patches, if the thrips have had time to grow, you may find adults flying around the grow room, or crawling on the leaves of your plants.


Check the underside of your leaves for insects that look like this. The bigger black bug is an older thrips, that is able to “fly” around the room, and land on other plants, and lay more eggs in their leaves.

When the babies hatch, they will all start to bite into your plants leaves, and suck the sap from it. This will leave you with small dots that can be confused for spider mites. Check for the silvery patches on the leaves, it’s a sure sign of thrips on a cannabis plant.

How to Treat Thrips on a Cannabis Plant

Thrips will grow through different stages during their life cycles. Eggs will be laid in the leaves, and babies will hatch, and feed upon the leaves until strong enough to change into the next stage.

Life cycle of thrips

At stage 3 and 4, the thrips will live in your medium. When this stage is over they will come up from the medium as full grown adults, ready to lay more eggs on your crop.

Thrips will also bring with them a risk of your plants catching a virus! If you have diagnosed your plants and you have a thrips infestation, you can treat it in the following ways;

1: Let the Medium Dry Out

As you can see in the images above, the thrips will spend the last part of their development stage’s in the medium. They like a moist place to live, and if there isn’t enough moisture they will die.

This can be the first step you take to fighting thrips on your cannabis plant. Let the top couple of inches of your medium fully dry out. If necessary, try feeding your plant from the bottom for a few feeds. This will allow the top of the pot to dry out fully, killing most of the thrips in the medium.

2: Diatomaceous Earth

Another way you can prevent the adults rising from the medium is to cover it with an inch of diatomaceous earth. This stuff must be kept dry to work effectively.

When the adult thrips try to emerge from the medium, they will have to crawl through the diatomaceous earth. It is made up of sharp particles that will tear and shred the wings of the thrips, and prevent them from laying any more eggs, and getting out into your grow room.

Be careful when us use diatomaceous earth, there can be health and environmental problems caused by it. You must use it with extreme care, and always use a face mask to prevent breathing it in.

You can find out more about the potential damage diatomaceous earth can have in the article from Peststrategies

3: Use Pesticides

Using a neem oil pesticide mixed with horticultural soap is always a good way to treat pests on your cannabis plants. To best battle thrips, you should spray your plant once every three days, for three treatments. This will stop the thrips breeding and laying eggs. They will eventually die off after about a week to ten days.

Spray your plants on the upper and lower side of the leaves, and also spray the top of the medium. Using neem oil pesticides, and diatomaceous earth together should get rid of the thrips on your cannabis plants.

When using neem oil pesticides it is important to keep up the routine! It will not kill the bugs instantly, they will stop eating, breeding and functioning normally. Make sure you are strict, treat every 3 days! Or they will be back.

4: Predatory Bugs

Sometimes you might be unfortunate enough to find thrips on a cannabis plant during the flowering cycle. In which case, spraying the plant with anything is not preferred! Instead, you can use predatory insects that will eat the thrips, but not your plants. You can purchase these bugs online:

Ladybird,Β Assassin Bug,Β Green Lacewing,Β Minute Pirate Bug

Using predatory bugs to fight thrips on a cannabis plant is very effective if you’re growing organically. But, these insects will leave waste behind, on your flowers, and it might be a good idea to wash your buds at harvest time to remove these contaminants.

Preventing Thrips

You will hear it may times, prevention is better than cure. Thrips some how got into your grow room. You need to figure out where they came from. Check all intake vents, and make sure they are covered, or away from open windows, where bugs can be sucked in.

Also, prevent going into your grow room if you have recently been outside. You can carry many bugs into the grow room yourself, and most of the time, either you, a friend or a pet has bought them in.

Many insect problems can come from collecting things from a grow shop! A lot of growers will head straight there when finding bugs, and thing can easiy be contaminated.

Before introducing any new equipment, or medium to your grow room, it should be treated with neem oil, or cleaned thoroughly. Take these precautions, and you will massively reduce the risk of thrips and other bugs on your cannabis plants.

Get Help in our Cannabis Growers Forum

Thanks for reading! You can find more information on anything related to growing in our cannabis grow guides. All of our guides are written by experienced growers, and members of our cannabis growers forum. If you have any questions, sign up. It is free, and we are always happy to help!

4 thoughts on “Thrips on a Cannabis Plant”

  1. Posted by: cloudy_kitchen

    awesome content as always mate, very helpful

    Thanks mate, getting stuck for ideas, even though there is still lots to write about lol. Took a nice break from writing now eager to get some more done, if you have any ideas, let me know πŸ™‚

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