Do not use iodine to treat blue disease

I lost a lot of money in treating blue disease with iodine. For example, 3 white orchid plants were purchased in 1994, and the petiole could not be cut off because of black spots. After planting, take iodine wine and smear the affected area with a brush, twice a day for 5 days. The disease was immediately controlled, but all died a few months later. Four plants of Dharma were purchased in 1996, of which 2 plants had black spots on their petioles and were treated with iodine to die. Two Jinhe plants bought in 1997 also died of iodine. For orchids with black spots on medium-and low-grade petioles, iodine is never used and grows well, which is enough to prove that orchids that die of iodine have the same symptoms. First brittle in the coating place, a touch will break, then the false corm rot, the whole plant withered, even clump strong grass, although not coated, but also shed the whole leaf. The reason is that although iodine has strong bactericidal power, it also has strong penetration and reaches the pseudocorm directly through the tissue. People die of alcohol poisoning, not to mention bluegrass? (old iron)