To get rid of white aphids - get a clove of garlic, blend with a cup full of water until very fine. Put the garlic water into a spray and spray the affeted parts. Do this twice a week until no more aphids remain.
Bicarbonate of soda is also good for getting rid of red spiders and other pests. Spray on the leaves of affected plants once a week.
White aphids which are actually live pests look like clotted powdered milk and stick to the stems and leaves of plants, killing them slowly. Most of my beautiful hibiscus have to be destroyed because of this pest. And cutting the affected parts is better than leaving them because the aphids will fly to other plants and infect them too. Once you have cut them, put them in plastic trash bags and either throw them or burn them. Since its the hot season now here in Malaysia (well Malacca anyway), we don't burn our rubbish. We don't anyway - usually the thrash is put in the biodegradable bags and the thrash man will take them away. Aphids love the hot season which is why there are so many just now.
My roses however are doing wonderfully. Most are in bloom though I can never get them to bloom as flourishingly as I always see them in the UK or US. Especially if you are there in summer - at Hyde park or the Regency Gardens.
I dare not use chemical pesticides because Chi Chi and Ginger love to eat the grass outside and Toi the tortoise eats the hibiscus flowers too. So no chemical pesticides for me. Our poor tortoise though have to hide under the bamboo leaves nowadays because of the heat. I have put a tray of water for it to splash in but maybe its too shy to come out. After all Repin likes to take it and put it out on the grass whenever it tries to come out at all. In fact at the beginning of the hot season, sometime in January I thought Toi the tortoise had gone away. He was no where to be seen for a few weeks at least. But about two weeks ago I caught sight of him hiding under a pile of dead leaves under the bamboo trees. Maybe its cooler there. What a relief! The Chinese believe that if a tortoise comes into your garden it is good feng shui. Our Toi has been around for almost 2 years now - since the big flood in 2006 when we were away doing our Haj. It must have been carried into the garden by the flood waters and decided to stay on for good. I hope for good anyway.