Another picture of the spores

Hi Mai, I am no expert but those look like hard armored SCALES, you can remove them with rubbing alchol 70% and spray with a systemic chemical, I use malathion, the plant will absorb it and make it non palitable. Bt alcohol always does it for me. Examine your plants every day and keep removing them just use the alcohol to wet a piece of cloth and wipe them off. I hope someone else chimes in. Velleta.

You have scale (hard shell or armored) insects. There are many different remedies, ranging from soapy water or alcohol through to the range of chemicals. Scale is not difficult to control, but you must be persistent.
Hard scale is a bit tougher than the soft (boisduval) type.
Address it quickly because scale can multiply and move from plant to plant incredibly fast.
Regards - Nancy

It's not the adults that you need to worry about. They are easy to see and to squash. However they laid eggs which will hatch into very vulnerable young scale. Spray the entire plant and the substrate with whatever you choose, Neem oil or whatever at weekly interval 3 times after eliminating all the adults you can see. Also look under the old bracts at the base of the pbulbs if that applies. If in one month there are no more scale, you were successful.

Nick

Thank you all for the advices. I'll probably start with soapy water, as it is the easiest one. Is there any kind of specific soap I need to get, or water + dish detergent (like Palmolive) will do? Can I soak the whole plant in soapy water, or is that too harmful to the plant?

Soapy water is good but remember it does not touch the adults. You need to get rid of them first and then use the soapy water to prevent recurrence.

Nick

Thank you, Nick. I'll do that.

I keep old spray-bottles handy with a mix of alcohol and Dawn and spray all my plants when different 'nasties' appear.....sally

Hi Sally,
What ratio of alcohol / Dawn / water? do you use for your spray?

I use 1/1/8 ratio

Nick