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Alabama Tree Crops-Current Low Chill Hour Accumulation a Concern


This year fruit growers may be experiencing the second warmest winter in over 60 years according to temperature data logged at the Chilton Research and Extension Center (CREC) since 1956.

Fruits have specific requirements for dormancy or “rest” which occurs during the cooler temperatures of winter, between 32° and 55° F. When varieties receive inadequate chilling they may experience slowness to break dormancy, with long (protracted) bloom period, slow leaf emergence and poor or varied fruit size development. This can be problematic for fruit varieties with high chill requirements.

As of Feb. 1, 2017, we will have logged 587 hours below 45° F at the CREC in Thorsby, compared to our 10 year average of 799 hrs, and our 59 year average of 997 hrs by Feb.1.

The Modified 45 Model for estimating chilling accumulation, which negates early, low quality chilling will only indicate 471 hours accumulated by Feb. 1, 2017. Current chill hour accumulations around AL can be viewed at: http://www.aces.edu/dept/peaches/peachipm/mesonet/ .

Management Strategies in Orchards with Inadequate Chilling

The following are management strategies to consider for some peach and other fruit varieties with high chill requirements and inadequate chilling. Fruit varieties with lower chill requirements may not require special management this year.

Consider spraying rest breaking compounds. Prune as late as possible. Do not prune all of the short shoots on high chill varieties since these have lower chill requirement buds. If flower buds on high chill varieties are not swelling or have aborted, do not prune until vegetative budbreak occurs to assure shoots for this year. If flowers have good stigmas, add bees to orchard with or without pollen inserts to overcome poor pollen availability.

Do not thin high chill (or marginally chilled) varieties until fruit have set and are growing (i.e., no bloom thinning). Fruit thinning should be done more carefully, over multiple occasions as fruit size differences become apparent.

Source: Alabama Cooperative Extension Service

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