fungus infection?
 

I have a dendrobium with this brown spots, not sure if is fungus or something eating them like mites. but new growths shown in picture 2 are very healthy. should I cut that leaves?

Hmm... could be fungal ...
Hopefully some other members will chime in!

Do not cut the leaves. The spots do not have yellow rings= it means the plant is not fighting infestation. This was probably caused by flying insects sucking on the leaf causing just a mechanical damage. The leaf can still produce food for the plant.

I am also want to know how can i remove fungus plants from my garden .Many time i have remove fungus plants but these plants grow automatically and effect others also. I have see related topic and decided to become a part of it because i want to know a proper way to remove fungus.Professional experienced company

fungus plants....do you mean mushrooms? If it is coexisting with other plants then its not a problem. It is when it becomes a problem that you can try to eradicate it physically with an electric hand mower or use a bolo knife and hack it all....