Ark, that makes no sense!

What the heck kind of bugs do you have that will not smother under the oil?

Why are you waiting so far between treatments? You not breaking the cycle of mites waiting that long between treatments.

Under optimal conditions ,approximately 80 degrees, the spider mites can hatch in as little as 3 days, and become sexually mature in as little as 5 days. One female can lay up to 20 eggs per day and can live for 2 to 4 weeks, laying hundreds of eggs. A single mature female can spawn a population of a million mites in a month or less.

I would treat a lot more frequently and make sure you are adding just the right oil. I would also use a natural soap so the oil actually breaks up and sticks to the leaves.

I hope this helps

Mike

Hello Ark. Spider Mites aren't too difficult ridding. An application of 2 drops dish soap diluted in water, sprayed every other week, or 'more often,' will kill them.
Daily spraying w/plain water, raising humidity, and an airy room should eradicate mites.

Ridding Leaf Miners is a lot more difficult.

I always thought LM'ers attacked plants grown in warm climates, but after researching I discovered they can be found anywhere. Especially if a plant is imported from a warm climate state, like FL.

About 8-yrs ago, people said LM's cannot be controlled or killed.
Since, theories have changed.

I found two websites that could help you.
They're ideas are drastic, but worth the effort controlling/killing LM's.

Some parasitic wasps eat LM's, 'which is one reason not to spray bee pesticides,' but I don't know where parasitic wasp live. lol

Another reason not to spray..LM'ers live inside leaves so it's unlikely sprays will afffect them.

Here's the drastic part. Remove and destroy affected leaves, which could possibly mean, every leaf on your Gardenia.
It'd be a hard thing to do, but worth doing if it means saving your Gardenia.

Oh, just found the name of the wasp. Diglyphus isaea. These wasps are commercially available. They eat LM larva.
It's also advised using Yellow Sticky Traps to catch egg-laying adults.

You might not want to bother w/wasps, lol, but removing leaves will hopefully save your plant.

Good luck, Toni

Here are the LM sites.

planetnatural.com

http://www.chemical-ecology.net/insects/leafmine.htm