Extreme temperatures can have a variety of impacts to agricultural crops. Our own human needs for additional water and sun protection translates similarly into what plants experience when they are out in a hot sunny field.
Plants can experience sunscald, resulting in damaged plant cells that form discolored areas on leaf or fruit surfaces. Sunscald is exhibited when climatic conditions are excessively hot and often coupled with intense sun exposure. Typically resulting in first a yellow or white discoloration on fruits or vegetables, sunscald can come on following the loss of plant leaves due to storms or other pest damage, or in cases where plant leaf growth is distorted because of nutritional imbalances or other plant damage.
Leaf scorch is another symptom that can be seen during hot and dry periods. This disorder results when the plant’s vascular system doesn’t have enough moisture to balance demands for cooling the plant’s leaf surfaces, through a process known as evapotranspiration. Patterns of damage with leaf scorch first appear on the leaf edges, but will eventually spread if no steps are taken. With both sunscald and leaf scorch, the damage observed on the affected parts of the plant will persist, however the remaining plant tissues can recover, and the plant can continue to survive and thrive.
Wilting of plants can also be a common symptom of plants exhibiting heat and moisture stress. Ensuring that adequate water is being delivered to plants, and water conservation practices like mulching and drip irrigation are employed as first steps to avoiding heat impacts to gardens and fields. Black plastic mulches and landscape fabrics can increase a plant’s water needs on intensely hot days, and it’s always a good idea to test the soil with your own observations to rule out an irrigation line problem if plants consistently look wilted.
Whenever plants are stressed, action needs to be taken in order to prevent the loss of the plant, or crops, in the field. Many plant diseases can cause leaf discoloration or wilting, so it’s important to differentiate among the plant symptoms you see. Plant samples sent to specialized labs, such as the NCDA’s Agronomic Division or the NC State Plant Disease and Insect Clinic can help determine if nutritional imbalances or pathogens are responsible, and nothing compares to the regular and attentive eye of the grower in the field. Field observations over time can clue you into growing problems BEFORE they take down an entire row of crops, and remember that N.C. Cooperative Extension Agents often can help grower’s assess and diagnose plant symptoms.
