Avocado Heat Advisory Temperatures are forecast to be in the triple digit range throughout much of the southern California avocado growing region beginning Sunday June 19 and extending into Tuesday June 21. The National Weather Service (NWS) is predicting maximum temperatures between 100 and 110 degrees with similar heat index readings away from the immediate coast for Ventura and Los Angeles Counties. In Riverside, San Diego and Orange Counties, NWS predictions are for 95 to 105 degrees in the valleys, and 105 to 113 degrees in the inland empire and high desert.
To ensure that California avocados maintain their superior quality it is imperative that growers manage their trees and harvest their fruit according to the best management practices as outlined below.
IRRIGATION Growers should be irrigating their trees now, in advance of the heat, to ensure that their trees are fully hydrated. An additional 50% of the budgeted amount of water is recommended to be applied the day before a heat wave. For extended heat waves, daily pulses of irrigation are recommended to maintain the trees' water status. A well-watered tree will tolerate the stress of a heat wave much better than a tree that is suffering from water stress. Signs of heat damage to trees include fruit drop, shoot damage, leaf burn and in severe cases leaf drop.
HARVESTING Every attempt should be made to harvest fruit when temperatures are below 90 °F, and no harvesting should take place when temperatures exceed 95 °F. Temperature in the shade should be monitored during harvesting and, when possible, harvesting crews should be moved to the coolest, least exposed areas of the grove.
Field bins should be placed under the trees while being filled to protect the harvested fruit from sunburn. Once filled, bins should be moved to a shade structure (open-sided roofed building), or covered with bin covers or light-colored tarps if they cannot be immediately transported to the packinghouse. Never leave filled bins exposed to the direct sun. The surface layer of fruit can easily heat up to more than 15 °F above ambient temperature when exposed to direct sun. Acute sunburn will only show on fruit after it is packed and is a major quality detractor.
To avoid water loss and decreased fruit quality do not hold fruit too long after harvest. Transport fruit to the packinghouse at least once per day, if not twice daily. Bins should not be left in the grove for more than 8 hours after harvest. Cover bins during transport to avoid sunburn and to reduce water loss.
Photos: Leaf sunburn, fruit sunburn
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