High temperatures

High temperatures are a major abiotic factor that acts as a precursor to severe physiological disorders in crops. While not a biological pathogen in the traditional sense, heat stress serves as a primary stressor that disrupts cellular homeostasis, triggers metabolic failure, and creates favorable conditions for secondary colonization by opportunistic fungi and bacteria.

The primary diseases and disorders resulting from heat stress include fruit and leaf sunscald, physiological wilting, blossom drop, and stunted growth. Crops such as tomatoes, peppers, potatoes, and wheat are particularly susceptible during heatwaves, leading to significant physiological damage that mimics infectious disease symptoms.

Biologically, high temperatures cause protein denaturation and the degradation of chlorophyll, which halts photosynthesis and halts plant development. The cycle of stress usually begins when ambient temperatures exceed the optimal physiological threshold for a specific crop, leading to rapid transpiration and the depletion of cellular water reserves.

Conditions conducive to heat damage are characterized by prolonged exposure to high solar radiation, low soil moisture, and high vapor pressure deficit. Damage is often more severe in plants that are poorly irrigated or in those that lack canopy coverage, exposing inner tissues to direct thermal radiation and dehydration.

The economic impact of high temperature stress is reflected in reduced yield quantity, poor market quality, and decreased shelf life of produce. Effective control measures focus on mitigation strategies, including the use of heat-tolerant cultivars, precision irrigation scheduling, shade structures, and the application of chemical anti-transpirants or stress-relief biostimulants during critical growth stages.