For some reason the last part of the message was cut off.

The root mealybugs STILL continued to appear again and harass my plants. Why? How?

Because it appears you have done all that you should your plants are being reinfected from some source. What is your soil source? Have you sterilized the soil before planting in it?
Bleach is a good disinfectant but would not do much to help with root mealybug.

Here is a link that might be useful: About root mealybug

I sterilized the soil with hot water, but I guess that's not good enough. I wanted to bake my soil, but my family wouldn't allow it since they have no clue what kind of smell it'll produce.

The soil source came from my own compost. The problem traced back to my very first plant 10 years ago, but I didn't realise it's a pest until the last 3-4 years.

I hear DE doesn't work when it's wet. It'll be nice to get a confirmation on this issue.

My main concern right now is the fate of my three uninfected pots, or at least they appear to be uninfected. It's a rosemary, a pair of bird's eye chili and a lilac tassleflower.

The soil source came from my own compost.

==>> soil is mother earth..

it is not really engineered for using in pots ...

one uses media in pots ...

sterilize your media .. when the family is NOT there.. lol .. i used a very large tin foil pan .. covered with aluminum foil.. with a few holes poked in it ... and there is very little smell ... other than damp earthiness.. which i like ... who cares about the family ...

i have also done smaller batches in the microwave ....

see link

if possible.. i would suggest you try to get some actual potting media ... if that is possible in Malaysia ... take some new cuttings .. and start from scratch ... and if you need to save old plants.. they need to be completely isolated from the new stock ...

i am presuming this is an outdoor project ... correct????

ken

Here is a link that might be useful: link

They are mainly potting material, plus compost and some bit of soil from a long time back. Changing the potting won't help if they lurk somewhere in the corner...

Pouring hot water over soils, commercial potting soils or your own mix, seldom will raise the temperature of that soil high enough, long enough, to kill any insect pests. Boiling water poured over soil less then 2 inches thick might be, but the temperature of the soil needs to get over 160 degrees.

i guess i am suggesting that they are IN YOUR COMPOST ...

so even if you are using a sterilized media.. you keep adding the problem back in by adding homegrown.. non-sterilized compost ...

why does your media need compost... this isnt along the lines.. of.. my children need to be fed .. so i am adding compost??? .. if so.. then you might be killing them with too much love ...

either use media ... or use compost.. but if you are repeatedly getting the same problem.. well.. you cant do w/o media.. so get rid of the compost ... it seems to be the only thing.. that you repeat.. which is leading to repeating the problem ...

the same holds true about what kim said as to temps .. as to whether your compost pile.. is actually properly composting whatever you throw in it.. composting.. is not just about stuff rotting.. there are attendant temperatures that need to be achieved .. for a compost pile to properly compost the material ...

ken