In general, plants can undergo stress condition which may either biotic or abiotic. Biotic stress factors mostly includes pest and diseases. It directly affects plant growth or has an indirect effects on photosynthesis. Pest affects plant physiology by influencing its water balance, sucking of plant sap from phloem elements, altering the sink demand and has autotoxic effects. Mostly sucking pest such as aphids, plant bugs affects the plant physiology more compared to other pest. Similar to pest pathogen also influence plant physiology to a greater extent. They has detrimental effects on photosynthesis, translocation of water and nutrients, upward movement of water, increase in leaf temperature due to reduced transpiration rate, clogging of phloem elements by pathogen particles which results in improper transport of water and wilting. Although biotic stress affects plant physiology, there are certain adaptive mechanisms that help in plants mitigating such stress. It includes signalling mechanism, systemic acquired resistance (SAR), role of plant growth regulators like salicylic acid, jasmonic acid and judicial application of mineral nutrients in the form of fertilizers.