Hi Malcolm,

I believe that the ratio is about 1 - 2% of limonene in water. I think that you would need to add something to dissolve or emulsify the limonene in the water as it's an oil and so doesn't mix too well with water. Probably some soap solution or something? Maybe someone else on GoY can correct me?

Have you considered using a natural predator during the warmer season like ladybirds to control the mealybug infestation?

thanks for your update on limonene Myron i will have to fish around on the web a little.i need not to make it too strong because its for tropical plants i grow and are verey sensetive thanks again mal

Personally, I don't think it will matter too much if you exceed a 2% ratio. It's a natural product and I don't think it will harm your plants even at 100%. I think that the stated dose is only for economy.... Why use more when a little will do the job just as well.

If you have only a few plants affected painting the bugs and their eggs with meths is quick, cheap and very effective. It does not harm cacti - can't speak for tropicals but worth a try.