More than 7 thousands of fungi species are responsible for this disease. A tell-tale sign of this problem is pustules of yellow, orange, and brown powdery pustules that can be found on leaves, fruits, and shoots. Even visually, the rust on the plants is kind of similar to the regular one. Rust rarely kills the plant but reduces its growth and affects its look. Mild and moist conditions are the most favorable for this fungal disease. That’s why rust disease spreads after watering because wet surfaces are generally suitable for fungi. Air is another way of spreading this disease because it is transferred by spores it has.