raffi stern - hcmuaf.edu.vnmain topics: • climate needs for growing subtropical fruit trees •...

Raffi Stern

Main topics:

• Climate needs for growing subtropical fruit

• Frost and protection from it

• Origin and distribution of species

• Reproductive biology (flowering, pollination,

fertilization, fruit development and maturity)

• Focus on avocado and litchi as representative

subtropical fruit trees (which also include

mango, date palm, banana, etc.)

Course syllabus: 1. Introduction to the subtropics: climate

adaptation, frost and protection from it

2. Avocado: origin and distribution, the 3 races of

avocado, reproductive biology – pollination

3. Avocado: reproductive biology – fertilization, fruit

set and development

4. Litchi: origin and distribution, differentiation, 3

flower types

5. Litchi: fruit development, fruitlet abscission,

vegetative propagation, cultivars

6. Field trip to avocado orchard (and

packinghouse)

1. Fruits of Warm Climate / J. Morton. Purdue Univ. USA, 1978.

2. Tropical Fruits / H. Nakasone and R. Paull. CABI, UK, 1998.

3. The Encyclopedia of Fruit and Nuts / J. Janick and R. Paull. CABI,

UK, 2008.

4. The Avocado: botany, production and uses / Whiley, Shaffer,

Wolstenholme. CABI Publishing, 2002.

5. The Mango; botany, production and uses / R. Litz. CABI Publishing,

(2nd ed.) 2009

6. Litchi and Longan: botany, production and uses / Menzel and Waite.

CABI Publishing, 2005.

1. Stern, R.A. & Gazit, S. (2003). The reproductive biology of the lychee.

Hort. Rev. 28: 393-453.

References : Books :

Article :

Book on

Subtropical Fruit Trees

http://www.hort.purdue.edu/newcrop/morton/index.html

Videos on Subtropical Fruit Trees (from Florida) Jonathan H. Crane

mango.htm-http://trec.ifas.ufl.edu/fruitscapes/video

http://trec.ifas.ufl.edu/tfphotos/

www.avocadosource.com

Climate

The temperatures and atmospheric

conditions (rain, humidity, wind,

radiation, etc.) prevailing in a certain

region over time

Climate is influenced by several

factors, such as: latitude, altitude,

geographic location (close to/far from

the sea), etc.

Subtropical and tropical regions

There are 3 main types of climate:

1. Tropical

2. Temperate

3. Arctic

Each region is generally divided into

several subclimates

The tropical region is defined schematically as lying between the tropics of Cancer (23.5° north) and Capricorn (23.5° south).

However, there are some exceptions:

•The Andes mountains at the equator.

• Israel, South Africa, California – at ca. 30° lat. and still subtropical

What are the climatic characteristics of

the tropical region?

I. Stable and high temperatures

1. Average annual temp. >25°C

2. Average temp. of coldest month >18°C

3. The difference between the hottest and coldest month is no more than 5°C

II. Heavy rain

1000-6000 mm annual rainfall

Near the equator there are 2 seasons:

1. Wet season (most of the year)

2. 2.Dry season (a few months)

III. Stable photoperiod

At the equator, daylength is always ca. 12 h.

North/south of the equator daylength changes:

The difference between longest day (summer) and

shortest day lengthens.

Nakasone and Paull, 1999

IV. Sun angle

At the equator the sun is at ca. 90° most of the

Therefore, irradiation is high and stable

vegetative growth throughout the year (heavy

cloud cover reduces strong irradiation).

• 0° (Equator) - High and

stable irradiation most

of the year (minimum in

• 20° - High irradiation

for 5 months (maximum

in May)

for 3 months (maximum

in May)

for 1 month (May)

V. High evaporation

High temp., heavy rain, long daylength and high

irradiation cause >80% relative humidity.

All 5 parameters result in high and stable

vegetative growth.

Subtropical region

Part of the tropics but more distant from the equator, roughly between latitudes 23.5° and

35°, even 40°.

There are a few sub-regions in the subtropical

region that have a: "Mediterranean Climate".

They include: Israel, California, South Africa

What are the climatic characteristics of

subtropical vs. tropical regions?

1. Hotter summer and colder winter.

2. Longer days in summer and shorter days in

winter.

3. Stronger irradiation (hot and dry summer

without clouds).

4. Lower humidity.

5. The average temp. in the coldest month is not lower than -3°C and not higher than 18°C.

Happens when the temperature drops to below 0°C.

When the temp. gets to -5°C there is

severe damage to trees such as avocado,

mango, litchi, banana, etc.

Subtropical orchards in Israel: Climate requirements

Frost damage in avocado trees

‘Ettinger’

(resistant)

it, 1968

‘Nabal’

(sensitive)

How do we get such low temperatures in

the subtropics?

There are two reasons:

1. Frost

2. Freeze

1. Frost

Occurs on cold, dry, clear (no clouds) and

without wind during night.

Under these conditions, a phenomenon termed

"inversion" occurs: the hot air from the soil

rises to the sky (lighter than cold air) and the

cold (and heavy) air remains near the soil.

1. Frost

The cold air is heavy and accumulates close to

the ground in the orchard.

Tree damage will be much worse at site B than

at site A.

2. Freeze

Occurs with the penetration of a very cold air

mass (from Russia to Israel, for example).

Temperature quickly drops to below 0°C.

The freeze not only harms the lowlands: all

areas are affected.

Factors influencing the extent of the

damage from frost or freeze

1. Temperature – The lower the temp. <0°C

and/or the longer the low temperatures last, the

greater the damage.

2. Species sensitivity – very sensitive: banana and mango (0°C extensive damage);

sensitive: avocado and litchi (-3°C damage

begins); "resistant": citrus (-6°C damage

begins).

3. Cultivar – avocado: 'Hass' is the most sensitive (-2°C), followed by 'Fuerte' (-4°C) and 'Ettinger'

(-5°C); mango: 'Kit', 'Maya' are very sensitive

(-0°C), 'Hayden', 'Kent' are sensitive (-1°C); litchi:

'Mauritius' more sensitive than 'Floridian‘.

4. Tree age – young trees are more sensitive than

mature trees

5. Tree health – "Green" and healthy trees are

more resistant than weak and chlorotic ones.

6. Crop load in the previous year – higher crop

load higher sensitivity

7. Temperature prior to the frost – low temp. (down to 0°C) before the frost can confer

resistance to the tree.

How can we see frost damage?

From slight leaf burn, through damage to the

fruit tissue, to death of the entire tree.

Damage of mature leaves

Browning of fruit stem

Damage inside the

fruit (Phloem+ Xylem)

Damage of thin branches

Damage of thick branches

Serious damage of ‘Fuerte’ (sensitive), but less in ‘Ettinger’ (resistant)

Damage of the rootstocks

Frost-protection measures

A. Before planting

Choosing the appropriate region (not in high

mountains or deep valleys), on slopes where

the "drainage" of cold air is good.

Topoclimatic map of the

Upper Galilee region

Central valley (blue): long periods <0°C

Mountains on the left (red): short periods <0°C

B. After planting

I. Before the frost event

1. Clear weeds – to allow quick passage of

the hot air from the deep soil to the soil

surface and to the tree canopy.

2. Protect the stem of the young trees,

including the graft union (0-40 cm from the

soil). We can use plastic, cardboard, etc.

around the stem.

B. After planting

I. Before the frost event

3. Funnel cold air out of the orchard using

passes in the lower orchard levels

B. After planting

II. During the night frost

1. Sprinkle over the top of the canopy –

start when the temperature goes down to +1°C and stop only after it comes back up

to +3°C and there is no longer any ice on

the trees.

B. After planting

1. Sprinkle over the top of the canopy –

B. After planting

2. Create air turbulence – using a

machine fixed at the center of the

orchard.

B. After planting

3. Create air turbulence using a helicopter

– the same idea but much more expensive.

Treatment of the tree after damage from frost

A. Weak damage

1. Spray a white covering to protect the

branches from sunburn.

2. Prune – only a little pruning of the small dry

branches .

B. Strong damage

1. New plantation.

2. Heavy pruning – only during the summer

after the new vegetative flush (if any).

3. Graft new scion after pruning.

4. Reduce amount of irrigation and

fertilization.

Pruned and whitened trees after the frost

raffi stern - hcmuaf.edu.vnmain topics: • climate needs for growing subtropical fruit trees •...

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