What are the control methods are related by Dr. Johnson?
Avoid the causal agent (quarantines, disease free stock, certifications etc.)
Reduce the population of the causal agent (sanitation, soil fumigation, rotation, etc.)
Protection (seed treatment, chemical control, irrigation management, row/plant spacing etc.)
Vector management (insecticides, nematacides, weed control)
Therapy (Heat treatment of seeds -loose smut- systemic fungicides)
Genetic resistance (R genes, partial or race specific)