Heat canker

Heat canker, also known as stem girdling, is a physiological disorder that affects young seedlings due to excessive surface soil temperatures. Unlike biological infections, this disease is caused purely by environmental stress, where the heat intensity causes the tissues of the succulent stem to collapse at the soil line.

This condition frequently impacts a variety of crops, with soybeans being particularly susceptible during the early stages of growth. Because the stem of a young seedling is tender and lacks the tough outer bark of a mature plant, it cannot withstand prolonged exposure to soil surface temperatures that often exceed 50 degrees Celsius.

The primary symptom is the presence of a dry, constricted, or discolored band at the soil surface level. This constriction effectively girdles the plant, cutting off the transport of water and nutrients between the roots and leaves. Consequently, the seedling wilts and collapses, often appearing as if it has been pinched by an invisible force.

The development of heat canker is strictly tied to specific environmental conditions: bright, clear, and sunny days combined with dry soil surfaces. Soils with poor thermal conductivity or low moisture content are more prone to reaching the temperatures necessary to induce this injury. Furthermore, small seedlings that do not provide enough shade for the ground around them are at the highest risk.

Mitigation strategies primarily revolve around cultural practices. Agronomists recommend planting at times when extreme heat waves are unlikely during the emergence phase. Additionally, ensuring good ground cover, optimizing plant spacing, and utilizing appropriate irrigation techniques can significantly cool the soil surface and protect young plants from heat damage during vulnerable growth stages.