In humans, good hygiene reduces spread: washing hands, covering the mouth when coughing and preparing food safely. Isolating infected people keeps pathogens away from healthy people. Vaccination protects people against pathogens. Killing vectors, for example with insecticides, reduces diseases such as malaria. Condoms reduce the spread of sexually transmitted infections.
In plants, infected plants are removed and destroyed. Crop rotation means growing a different crop each year, so pathogens in the soil build up less. Plants brought in from abroad can be kept apart and checked, which is called quarantine. Farmers also use chemicals that kill insect vectors, and grow disease-resistant varieties.
Quick detection helps control spread. Visual identification uses symptoms such as spots, galls or white patches. A test can detect an antigen, a molecule on the pathogen. DNA testing identifies the pathogen from its DNA, even from a small sample.