Agriculture: Alfalfa Pest Management Guidelines

Scald (Flooding and High Temperature Injury)

  • none (abiotic disorder)
  • Symptoms and Signs

    Symptoms of scald include an off-color of the foliage and wilting, even though the soil is wet. Roots may rot and have a putrid odor when removed from the soil. The water-conducting tissue of affected roots die and becomes brown.

    Scald is often confused with Phytophthora root rot because both occur in saturated soil conditions, but if temperatures have not exceeded 100°F, it is probably not scald.

    Comments on the Disease

    Scald is related to the combination of high soil temperatures and length of time soil is saturated with water. When air temperatures are in the range of 104 to 113°F, alfalfa is extremely susceptible to flooding injury. Scald is usually limited to hot desert valleys, such as the Imperial and Palo Verde Valleys, when soil is saturated for long periods after irrigation or rainfall. Affected plants may die within 3 or 4 days after irrigation.

    Fields that have been recently mowed are much more susceptible to scald than fields closer to harvest.

    Management

    The primary control measure is proper water management.

    • Irrigate at night, when temperatures are cooler, or during the day for relatively short periods (e.g., 4 hours) when temperatures are high to reduce the likelihood of scald. Some soils, however, remain saturated long after irrigation because of heavy texture, slope of the land, and length of the irrigation run. Avoid irrigation when temperatures are over 109°F. Drain excess irrigation water from fields as soon as possible to avoid water ponding during periods of high daytime temperatures.
    • Do not irrigate newly-mowed plants until enough regrowth occurs to prevent submersion of entire plants.
    Text Updated: 03/17