Pest includes

• Pathogens
• Insect pests or non-insect pests
• Parasites (including weeds)

Disease

• Disease is an abnormal condition in the plant produced by an organism.
• Diseases are produced by a variety of organisms from both plant and animal kingdoms, viz, fungi, bacteria, viruses, nematodes and insects.
• Diseases reduce total biomass production and economic yield up to 100% of the crop in one or more ways of Killing or damaging of leaf, branches, reproductive units or whole plant.

How disease develops?

• The development of any disease depends on a close interaction among three diverse factors: host, pathogen and environment

Up to when a cultivar remains resistant?

• Coevolution of pathogen and host natural evolution which develops resistance plants also being coevolution of pathogens
• A non-resistant variety may disappear.