2013 Peach Review & Upcoming ChallengesDr. Mercy Olmstead, UF/IFAS Extension

2013 Winter Pruning Workshop

2013 Weather

Warm…then cold!

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Citra, FL

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Lake Alfred, FL

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Fort Pierce, FL

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How Do We Accumulate Chill?

Different varieties require different amounts of chill

Flower buds need less cold weather than the vegetative buds

Vegetative buds are necessary for good fruit quality, so this is often what contributes to poor sugar accumulation and flavor development in low-chill accumulation years.

Carbohydrates produced via photosynthesis = sugars for fruit

Ecodormancy

Buds on the fruit or nut tree/bush/vine are dormant due to environment.

Water stress

Cold temperatures

Shortening of the daylength (photoperiod)Photoperiod – length of light and dark periods affect plant processes

Endodormancy

Buds are dormant due to internal physiological blocks

Despite ideal environmental conditions

Chilling conditions above freezing end physiological block

Advantages:

Keeps plants dormant during fluctuating temperatures

Subtropical climate and frequency of entering this stage?

Chilling requirements

Measured based on different models

Standard method – chill hourAnything less than 7.2°C = chill unit accumulation

Utah chill model (Richardson et al., 1987)Temperatures between 1.6-12.5°C promote chill accumulation

7°C is ideal (1 hr. @ 7°C = 1 chill unit)

Dynamic method – chill portione.g. 1 portion = 28 hours at 6°C

More recent, used with chemical rest-breaking agents such as hydrogen cyanamide (cherries in California)

Utah Chill Model

Allows for addition and subtraction of chill units accumulated over winter

Temperature Chill Unit

< 34.5°F 0.0

34.7 – 36.5°F 0.5

36.6 – 48.4°F 1.0

48.5 – 54.3°F 0.5

54.5 – 60.6°F 0.0

60.8 – 64.4°F -0.5

> 64.5°F -1.0

Frost Events

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Citra, FL

February 12, 2013 = 27 degrees February 13, 2013 = 22 degrees

Precipitation and FloodingJune 1 – August 1, 2013

FAWN Station Rainfall (in.)

Citra, FL 23.85

Lake Alfred, FL 26.95

Fort Pierce, FL 18.48

Washed out nutrients in the soilStunted treesRoot damage from flooding = early defoliation, early bloom

Effect of Fertilization Method on Growth, August 2013

Fertilized Monthly Split Application - June

Weather Effects

Frost reduced potential yields

Warm winter = extended bloom period

Diseases and insects worse with precipitation in late June/July

Leaf rust

Scale

White Peach Scale

Upcoming Challenges –Early Bloom!

Be sure to get your oil sprays on for scale control – those that sprayed it did not appear to defoliatetrees.