Black spots on orchid flowers

Q: I placed a large flowering cattleya on a shaded, covered patio. Flowers last a long time but developed small black spots all over the blooms. What caused this? A: Petal blight, caused by a Boltrylis fungal species, is common during cool, damp weather where there is inadequate air circulation. Phalaenopsis and Catttleya-like flowers are most susceptible. Cut off and destroy all blooms showing infection. Spray with Physan 20 at the rate of 1/2 Tbsp/gallon water.