i need help with disease or fungus
 

i have been growing orchids for 15 years but am not a "pro". i have been disease free for all that time but now i have something spreading from orchid to orchid. started with the phals and has spread to the dendrobiums. i have used physan 20 and an orenex systemic. it seems to have slowed it. the leaves have light spots underneath and then they start to show on the top of the leaf. it spreads and the leaf turns a mottled yellow. it is really hot here and hard to cool. i am afraid it is a fungus. any ideas. i am at work or i would post a photo.

carol:scratchhead:

You may be experiencing an outbreak of virus or fungus. You should move the plants away from one another to keep the foliage from touching. plants that are afflicted should be removed from the greenhouse or growing area to a shady spot beneath a tree or to another room in the house. treat them with a drenching of Physan and allow them to dry. If the leaves begin to blacken it may be fungal but if they are only discolored and the plant is still growing it is most likely viral and you will need to destroy the affected plants. Also use a solution of bleach to washdown the growing area. treat the unaffected plants with physan as well to prevent any further spread. When its heat stress an entire plants should yellow not just ptches on a leaf.

Try this link and see if it matches any of the symptoms that you are observing on your plants.
It is possible that the plants are just overheating, or suffering some form of mineral deficiency.


Diagnosing Orchid Problems