Food Grade Diatomaceous Earth
 

I've been having good results using a sprinkling of DE to kill mealybugs.

Advantages
- chemical free and people friendly
- lasts indefinitely, does not have to be reapplied providing care taken
- kills all orchid- related pests, even scale
- no impact on treated plants
- can be easily washed off/away
- apply with fingertip to undersides of leaves

Disadvantages
- application not hassle free
- appearance on plant leaves could put people off
- deactivated if wet/watered.

Background
Diatomaceous Earth (food grade): Bug Killer You Can Eat!

I believe this is so effective because mealybugs are so active at night.

Extreme application.
This delenatii was driving me crazy as I could not
completely eliminate a mealybug infestation. Even after weekly applications, like 7 times.
This DE application - about 7 weeks ago - has completely eliminated the mealybugs. None.... anywhere. Of course this is extreme and I will probably wash it away in a month or 2. The appearance of the plant does not upset me at all!

I've never heard of using DE for mealies. Worth a try.


Judi

That paph is hilarious!

Are you SURE it's killing the mealy bugs and not just giving them camouflage?

I wish I had heard about DE back before I lost my GH. I was fighting mealy bugs back then and seemed to have no success. I had them on a Miltonia and could not eradicate them. I used an insecticide which seem to work only to have the bugs come back a few weeks later.

I did find that the bugs did not attack Cattleya's. It must have been their tough leaves that deterred them.

Right now, my orchid collection (all of 6 plants) is insect free and I am hoping to keep them that way.

I've only heard of diatomaceous earth being used for slugs in the garden, never for insects. And why does it need to be food grade? It can be found in any good garden center. It is also used in aquarium filters to filter out diseases.

Must be food grade because that's not harmful to people/pets. Non food grade apparently has a higher concentrate of silica and is dangerous in dust form. It's not that expensive online so food grade is "better safe than sorry" in my opinion. You can research the differences and come to your own conclusions

Diatom skeletons are 100% silica, no matter what the grade. I think the primary difference between food grade and filter grade is the reduced levels of heavy metal contaminants in the former and that the SiO2 tends to be amorphous rather that crystalline, but I'm not certain about that part.

However, that has nothing to do with the selection for use as a pesticide. That is because the filter grade stuff has been exposed to additional processing and the particles are more rounded and less "spiked", so do less damage to the bugs.