Heat burn

In corn, heat burn frequently presents as bleaching along the margins of the leaf blade, which progressively moves toward the center. Under extreme temperatures, the leaves may curl into a tube shape to conserve moisture.

Unlike infectious diseases, heat burn symptoms appear abruptly across entire fields, specifically affecting plants exposed to intense sunlight or hot, dry winds.

During early stages, tissues may look water-soaked or wilted, eventually turning into papery, necrotic patches. In severe cases, premature senescence of lower leaves occurs.

During extreme heatwaves, damage to the growing point can lead to stem deformation and the failure of corn plants to produce healthy, filled ears.

Heat burn is not an infectious disease and is not caused by fungi, bacteria, or viruses. It is a physiological disorder resulting from environmental stress factors.

The main trigger is a combination of high ambient temperatures (typically above 35–40°C) and low soil and atmospheric humidity. The plant loses water through transpiration faster than it can absorb it from the soil.

This imbalance forces stomata to close to save water, leading to tissue overheating. Consequently, the internal metabolic and enzymatic systems of the plant cease to function correctly.

Within the plant cells, protein denaturation occurs, leading to cell death. This process of cellular collapse is what manifests visually as necrotic leaf spots.

High solar radiation acts as a catalyst, intensifying the overheating effect, especially during growth phases when the leaf surface area is at its peak.

The condition develops under prolonged drought and heat. Hot, dry winds (desiccating winds) are particularly dangerous as they rapidly increase the moisture deficit.

Crops are most vulnerable during active growth stages and reproductive phases. For corn, the period of silking and pollination is particularly critical for yield potential.

Soil type plays a significant role: sandy soils lose moisture faster, causing plants to hit the wilting threshold much sooner during heatwaves.

Poor agricultural practices, such as high planting density, increase competition for water, leaving plants more susceptible to thermal injury when resources become scarce.

Excessive fertilizer application can sometimes lead to an oversized leaf canopy, which becomes a burden to the root system when the plant is unable to sustain high transpiration rates.

The primary damage is a drastic reduction in the photosynthetic area, which slows down biomass accumulation and significantly reduces overall yield.

In corn, thermal stress during flowering causes a lack of synchrony between pollen shedding and silk emergence, often resulting in poor kernel set and empty cobs.

Plants weakened by heat are highly susceptible to secondary infections, as necrotic tissues provide easy access for opportunistic pathogens like fungi and bacteria.

The disruption of nutrient translocation from leaves to the grain negatively affects kernel weight and quality, leading to reduced market value.

Prolonged heat stress depletes the plant's adaptive reserves, leaving it more sensitive to other environmental stresses for the remainder of the growing season.

Effective management begins with irrigation in critical growth stages to maintain plant turgor and reduce the localized air temperature within the crop canopy.

The use of anti-transpirants and growth regulators containing amino acids can help plants stabilize metabolic processes and maintain integrity under thermal stress.

• Optimizing planting density to reduce water competition between plants.
• Implementing crop rotation to maintain soil structure and moisture-holding capacity.
• Applying balanced potassium fertilizers to strengthen cell walls and improve drought tolerance.
• Selecting heat-tolerant corn hybrids specifically bred for hot climate conditions.

Soil mulching techniques can significantly reduce surface evaporation, helping to protect the root zone from excessive heating.

Regular weather monitoring allows for proactive management, such as applying foliar micronutrients to bolster the plant's natural defense systems before a heatwave strikes.