There not allways is happiness and joy with your orchids. There unfortunately are diseases, and pests which can attack your plant. It's good to know them, so you can do something against. I have listed some of the most important ones.
Greenfly
The greenfly can enter through open windows in the house or settle down when you keep your orchids outdoor. They prefer young leaves ,buds or young shoots and suck there the sap. This comes to a damage of the orchid. The best is to get rid of them under running water or get them of by a soft brush. If it's even worse you can use a pesticide but read carefully the instructions. There are some orchids which doesn't like pesticide which contains oil. You also can mix your own mix with soft soap. The plant should be isolated until all the greenflies are gone otherwise they settled over to other plants. You should control the plant after the treatment. Make sure that no other greenflies have hatched out from eggs.
Spider mite
The spider mites are quite small and settle down on the bottom of a leaf. There they suck the cell sap from the plant. If one notice this too late, it's possible that the leaf alread is dry and fall of. The spider mites prefer dry air, so you often have them during heating period. To get rid of them: give more humidity in the air or put the plant in a plastic bag. This moist condition kills the spider mites. There are also some sprays to kill them or you buy some killer mites.
Meal bug
It's not hard to recognize mealy bugs. They look like many-legged blobs that have been rolled in flour. You'll see them creeping slowly along stems and the undersides of leaves, and find their eggs suspended in cottony sacks. Some also attack roots.
I take the bugs carefully off from the plant, using a soft brush. I mix water with soap and alcohol. You must do the whole procedure up to 3 times because there are still some hidden eggs and young animals could continue the circle of life
