Why Are Pecans Alternate Bearing?

1
Why Are Pecans Alternate Bearing?
2
We will cover.

• 1 What is alternate bearing?
• 2 Why does it occur?
• 3 How do we stop it, slow it, or manage it?

3
What is Alternate Bearing?

• Alternate Bearing- the tendency for wide cyclical
  swings in yield
• Referred to as
• On and Off years
• Good and Bad years
• Heavy and Light years
• Related terms
• Biennial bearing, irregular bearing, masting
• (every other year)
  (scattered years of production) (insect
  trickery)

4
Is Alternate Bearing Bad? --- Ecological
Perspective

• Alternate bearing in the wild
• Oak, beech, pine, elm, hickory
• Advantage
• Pest suppression (less babies, less food for
  pests)
• Assures a good crop every other year

5
Alternate Bearing Whos Guilty?
Nuts Temperate Fruits Sub-Tropical Fruits Tropical Fruits
Hazelnuts Apples Avocados Litchis
Pecans Apricots Citrus Mangos
Pistachios Pears Olives
Walnuts Prunes
Source Monselise and Goldschmidt, 1982
6
What does alternate bearing look like for mature
trees?
7
How are TX pecans doing?
8
Affects of Alternate Bearing --- Horticultural
Perspective

• It Hurts Every Level of the Pecan Industry!
• Pecan tree health
• Too much growth during off years may cause
• Freeze damage (rare, but possible)
• Limb breakage (combo of leaf/stem weight and
  drought)
• Tree collapse
• Too little growth during off years result in
  less production the following year.
• Pecan processors and contract harvesters
• Facilities/equip. run below capacity in off
  years.

9
Affects of Alternate Bearing --- Financial
Perspective

• Fluctuations in Quality
• Small, poorly filled nuts
• Premature germination
• Shuck decline
• Instability of cash flow

Average In-Shell Pecan Price 1992-2009 Average In-Shell Pecan Price 1992-2009 Average In-Shell Pecan Price 1992-2009 Average In-Shell Pecan Price 1992-2009 Average In-Shell Pecan Price 1992-2009 Average In-Shell Pecan Price 1992-2009
On Years On Years 0.89/lb
Off Years 1.17/lb

10
Why does it occur?
Management Avoid triggering events- if
possible.

• Severe infestations of nut-eating insects
• Late frosts
• Early spring hail storms
• Severe drought
• Severe lack of nitrogen /or zinc.
• Severe foliage feeding insects.

Trigger (e.g. Hail)

On
On
On
On
On
On
Off
Off
Off
Off
Off
Off
11
Why does it occur?
Management Orchard setup.

• Dense populations of trees causes
• Competition for nutrients
• Competition for water
• Competition for light
• Over-production of nuts
• Excessive vegetative growth
• Mono-culture regarding
• varieties

12
Why does it occur?
Cultivar Alternate Bearing Intensity (I)
Barton 0.36
Bradley 0.56
Burkett 0.29
Cape Fear 0.53
Cherokee 0.91 (worst)
Desirable 0.40
Elliot 0.68
Gloria Grande 0.27 (best)
Mahan 0.74
Moneymaker 0.68
San Saba 0.85
Schley 0.60
Stuart 0.47
Western Schley 0.56
Wichita 0.67

• Management
• Best varieties
• Smaller nuts

13
How do we stop it?

• Insect Control
• Aphid
• Fall-Webworm
• Shuck worm
• Disease Control
• Scab
• Mildew
• Irrigation (minimum of 1/wk.
• Use a rain gauge
• Irrigate if feasible
• Start - June 1, End - Sept. 15th

Source entoplp.okstate.edu
14
How do we stop it?

• Plant several varieties
• Include small-kernal varieties
• Include some low alternate-bearing
  index varieties
• Soil Testing/Tissue Analysis
• Zinc nutrition
• Nitrogen nutrition
• On vs Off year rates?
• Late season application?
• Proper pruning and thinning of
• trees, and possibly thin fruit in heavy years.

Source entoplp.okstate.edu
15
What about next year?
?
Edited by Vincent Mannino, County Extension
Director Fort Bend