Why do nutrient deficiencies make plants more vulnerable to pathogens?

In the field of plant pathology, nutrient deficiencies are considered noninfectious causal agents that disrupt a plant's normal physiological and biochemical processes. When a plant experiences a deficiency or an imbalance of essential mineral nutrients, its normal growth and function are impaired, which often renders the plant more susceptible to infection by pathogens.1

Environmental disturbances, including nutrient imbalances, alter the plant's normal physiology and its host-pathogen interactions. Because plants require specific minerals to develop and mature in a healthy state, a lack of these elements can lead to symptoms such as stunting, leaf malformation, and dieback. These weakened states create conditions where the plant is less capable of defending itself, making it more vulnerable to both primary pathogens and secondary invaders.21

Essentially, when a plant's essential systems are compromised by poor nutrition, it loses the robustness needed to resist environmental stressors and biological threats, effectively lowering its threshold for disease development.1