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Excessive Heat, High Winds and Fire Weather Warnings Issued in Southern CA

California Avocado Commission — The National Weather Service has issued warnings concerning an extended period of excessive heat, gusty winds and critical fire weather conditions beginning Monday, June 14 and lasting throughout the entire next week for the Los Angeles/Oxnard region.

Beginning Monday, the region will experience higher temperatures and gusty winds, peaking Tuesday through Friday, June 18. The combination of extended high temperatures — in the triple digits — warm overnight temperatures, low humidity, abnormally dry fuels and Sundowner winds will create critical fire conditions during this time period. The Sundowner winds in Santa Barbara County and north winds along the I-5 corridor and the canyons and hills of the Santa Ynez Range and Santa Clarita Valley could create gusts in the 30 – 50 mph range. Driving conditions also could become hazardous due to downed branches or power lines.

The highest temperatures will occur Tuesday through Friday with highs between 98˚F – 108˚F in the valleys and mountains. Overnight lows will be between 65˚F– 75˚F. Humidities will range from 8 – 15%.

These conditions will post a high risk for heat-related illnesses for those working outdoors.

For more information on how to avoid these risks, view “Reduce Heat Illness for Employees” on the California avocado growers’ website.

To ensure California avocados maintain their superior quality it is imperative growers manage their trees and harvest their fruit according to best management practices as outlined below.

IRRIGATION

Growers should be irrigating their trees now, in advance of the heat, to ensure their trees are fully hydrated. It is recommended that an additional 50% of the budgeted amount of water 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.

For more information about managing heat in avocado groves, growers can view the following articles on the California avocado growers’ website:

•    Managing Heat in California Avocado Groves
•    Managing Avocado Heat Damage
•    Best Practices for California Avocado Groves Impacted by Excessive Heat

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