Question
i leave in a tropical island,and have a number of roses in pots as my soil is a rock ground. its hot from June to November,and cool from December to may
when is the moment of pruning?
they are flowering all the time but are sick now with black spots and have red spider what should i do?
i don't use chemical insecticide because of the birds

i inherited those plants from my sister who used to live in the mountain where it cool all year. and i live down where it hotter.. thanks in advance for your answer
Marie

Answer
You are going to have quite a challenge to grow roses without any problems in your area. One of the problems you are facing, which is also causing the insect one too, is that roses will go under stress in high heat and shut down their roots to stay alive. That means they don't take up any nutrients and not much water.They are under more stress  because they are planted in pots and that gives them warm roots which roses dislike. Roses really only need about 6 hours of full sun so I would place the pots in an area that gets the sun in the morning but not in the heat of the afternoon. I would then place something around the base of the pots that looks attractive, to try and keep the roots cool.
The black spots are a fungal infection called Black Spot and many roses are prone to it if conditions are right. There are sprays to help cure it, but if you are not wanting to use them, then try spraying them with baking soda and water. 1 tablespoon to 1 quart of water. To discourage spider mites you try and keep the leaves wet as they hate dampness or water. Take the hose and wash the roses down daily until they are gone. After that start your spraying with the baking soda. If this doesn't work, you can also use garden sulphur as it is a natural substance and won't hurt the birds at all.
Roses usually like a resting period and the best time is when the weather is the coolest. That is also the best time to prune the roses back. Because you have a bad case of Black Spot and also because the roses are in pots and the roots crowded, cut the rose bushes right back to 12 inches. The reason is that the roots can't sustain a large rose bush if the rose is planted in a pot. Ideally the pots should be at least 24 inches across. Hope this helps.