pyrethrum bomb during flowering

Pyrethrum Bomb During Flowering – Is It Good?

While cultivating cannabis, you may face spider mites and other bugs at some point.

Mites and bugs can be annoying and disastrous as well. A bad infestation of bugs will destroy all your hard work. 

Pyrethrum is a popular solution to keep the bugs off. However, you might ask, “Can I use a pyrethrum bomb during flowering?”

Yes, you can use pyrethrum bombs during flowering. You need to follow proper guidelines for that. Also, it is advised to use it during the late stages of flowering, around 4-6 weeks. However, it’s prohibited to use it within 3-4 weeks of harvest. Spraying the formula early in the morning is the ideal time. 

That will be the summary. I have discussed the whole topic in this article just for you.

Stick with me till the end to find out everything.

Let’s start.


  • Don’t use pyrethrum bombs in small spaces.
  • Be careful about using pyrethrum in the early stages of flowering.

Can I Use Pyrethrum Bombs During Flowering?

The simple answer to this question is “Yes”. You can use a pyrethrum bomb during the flowering phase. 

But there is a catch. You need to follow proper guidelines or your plants will be destroyed. 

In just a few hours, pyrethrum decomposes completely and has zero impact on reflecting surfaces. However, it is phytotoxic and will kill the plants if used in too small an area.

spraying pyrethrum on cannabis
Source: mygardenplant

Moreover, we do not recommend using them unless you are experiencing an infestation in the later stages of flowering (weeks 4–6). Use them only as a last resort. 

This is because using them creates generations of new mites that are immune to them. Because when mites smell it in the air, they frantically lay eggs before they die.

When Do I Need Pyrethrum Bombing?

The pyrethrum is generally used as the last resort to push out bugs from the plantation. These bugs might prevent the calyxes from swelling. Professionals don’t recommend it before the later stages of flowering. This time is around 4-6 weeks of flowering.

However, some growers do experiment with seedlings! Here’s one for example-

It’s effective for big regions and can reduce an overwhelming infestation to a more manageable level. 

You might have a question, Does pyrethrum kill aphids and thrips?

One of the most efficient weapons against thrips is the pyrethrum. This can be used alone or in conjunction with other compounds. Use a pyrethroid pesticide spray (resmethrin, permethrin, cyfluthrin, and others). The aphids and any predators will perish as a result.

An image of spider mites on cannabis
Source: growweedeasy

Everyone who tends a garden knows that insects lay eggs that won’t hatch for a few days or weeks. Hence, this method isn’t 100% effective all the time. 

The process will require multiple iterations. You will need to spray once a week with a patrol solution.

Is It Safe to Use Pyrethrum Bombs in a Small Indoor Growroom?

Don’t make the error of placing the insect bomb inside your grow tent and closing it up. This will not increase the effectiveness of the bomb. 

If you aren’t careful, you can end up killing your plants. The recommended treatment area for this fogger is 3,000 square feet.

The suggested usage multiplies by a factor of one hundred if you put it within a 5×5 grow tent. The leaves inside the grow tent will be coated with it and suffocate. 

The leaves will have a pale yellow/black color and eventually die. When using a bug bomb on a grow tent, the tent door must be left open. 

Also, the fogger must be activated outside the tent, at least two feet from the plants. Your tent may benefit from a breeze provided by a fan. 

While you’re treating the area, don’t forget to switch off the fan. To avoid going back into the room before the air is clean, try to schedule a fan. 

Also, you can schedule a carbon filter to turn on approximately an hour later. 

So, does pyrethrum harm plants?

Pyrethrum does not hurt plants if it is used solely in the field with targeted sprays. Furthermore, they have a short-lived impact on plants since they break down naturally or after cooking.

If you leave it out overnight, the expanding liquid will leak into other house areas. This will contaminate the air you breathe. No issue, this will treat a whole 10×10 or 15×20 room.

Pyrethrum Bomb Solution Preparation

You can prepare the solution in two ways: buy it or make a homemade one. Both of the solutions have the same effectiveness and usage.

I have tailored the solution preparation guide just for you.

Pyrethrum TR Fogger:

With Pyrethrum TR, grow operations may take advantage of the efficacy and convenience of a total-release fogger. This allows for rapid, comprehensive coverage; exceptional plant safety; reduced worker exposure; and quick re-entry times.

A bottle of pyrethrum concentration
Source: scintex

Additionally, micro foggers cut down on operational costs. Because there is no need for costly fogging equipment maintenance or repairs. As well as no need for chemical mixing or cleanup. 

There is a 3,000-square-foot coverage area for a 2-ounce can of Pyrethrum.

If you want to use the Pyrethrum TR spray, you will need to sanitize your plants first. You will need to turn on the total release action for maximum effectiveness. Similarly, you can check out BASF Pyrethrum TR Fogger as well.

Home-Made DIY Solution:

Making a pyrethrum bomb at home is pretty easy. You need to pick the Cinerariifolium flowers right after they blossom. Then dry the heads on newspaper in the sun. You’ll have the most pyrethrin content possible for your homemade spray or dust.

Once the flowers have dried, crush them up using a mortar and pestle. Do this to make a fine powder and then sprinkle it on your plants with a sturdy spray bottle

But do you know how to use pyrethrum bomb TR fogger?

For spraying, combine 1/2 cup of dried flower heads with 1 liter of boiling water. Let it cool (approximately three hours), filter, and then mix with 1 teaspoon of pure soap. 

The soap improves leaf cover and boosts productivity by a factor of four. This will give a good yield rate per foot of the plant. Prepare the spray accordingly. 

However, do keep in mind that you will need to use the spray right after the preparation. Storing it will nullify the effectiveness.

How to Use a Pyrethrum Pesticide on Plants?

Users must exercise caution while applying any insecticide. A handful of the best applications of pyrethrum for plants are detailed here.

How to Use a Pyrethrum Pesticide on Plants

Spraying Early in the Morning:

You can use a botanical pyrethrum insecticide to spray for flying insects before sunrise.

Apply pyrethrin pesticide directly to the afflicted plants using a hand sprayer. Do protect yourself with a respirator or self-contained breathing device. This level of visibility is essential for effective and widespread pest management.

Honeybees, ladybugs, and other beneficial insects can be shielded from pesticides. This can be done by covering treated plants with an old sheet or row cover. 


A minimum of 24 hours of plant coverage is recommended for the complete elimination of pests.

Soft Spraying: 

As the nymphs congregate in these “hot zones,” spraying there is an effective method of control. Vegetable and fruit crops under assault from whiteflies or other swarming insects should have spot treatments applied.

Liquid Solution:

The organic pyrethrin concentration, in liquid form, is recommended by many. Though it is widely available in dust form. To use, combine the pyrethrum powder with a soapy water or oil mixture (as recommended by the manufacturer).

The liquid version, however, is much more effective than the powdered one. This also gives protection against different types of pollinators. These include bees and butterflies.

To sum things up, I have prepared this quick table just for you.

Spray Time Early in the Morning 
Amount of Pyrethrum 2 oz./ 3000 sq. ft.
Usage Frequency Once Every Week
Additive3% Azatrol Solution

I hope this helps you with your project!

Frequently Asked Questions (FAQs):

Is Pyrethrum Spray Safe?

When applied topically in doses of less than 2 grams, pyrethrum may be safe. Side effects from pyrethrum include headaches, ringing in the ears, nausea, and tingling in the fingers and toes. This also includes breathing problems and other nervous system issues. However, the herb’s low toxicity at therapeutic levels.

Will Bug Bombs Hurt My Plants?

No, it will not hurt your plants. Insecticides and pesticides are common components of bug bombs used to rid your home of unwanted pests. You can buy them under a variety of labels. However, it is advised that you and your pets leave the home when used.

What Happens If I Use Too Many Bug Bombs?

When foggers are overworked, the resulting vapors become overwhelming. It only takes a spark from a pilot light, heater, thermostat, or water heater. Or any number of other sources to start a fire or explosion. Please read all of the label’s precautions before use.


That will be all on pyrethrum bomb during flowering. Hopefully, you have understood the process and can spray them on your plants. 

Whatever you do, make sure you use them as a last resort only. And do not use it before 4-6 weeks.

See you soon.

Leave a Comment

Your email address will not be published. Required fields are marked *