Why Are Pecans
Alternate Bearing?
We will cover….
 1 – What is alternate bearing?
 2 – Why does it occur?
 3 – How do we stop it, slow it, or
manage it?
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)
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
Alternate Bearing: Who’s 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
(Millions of Pounds) l
In-Shell Yield
700
600
500
400
300
200
100
0
Walnut
20
06
20
05
20
04
20
03
20
02
20
01
20
00
19
99
19
98
19
97
19
96
19
95
19
94
19
93
19
92
19
91
(Millions of Pounds) l
In-Shell Yield
700
Pecan
600
500
400
300
200
100
0
What does
alternate
bearing
look like for
mature
trees?
How are TX pecans doing?
Yield
(Millions of Pounds)
l
California
New Mexico
Texas
100
80
60
40
20
0
91 992 993 994 995 996 997 998 999 000 001 002 003 004 005 006
9
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
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.
Affects of Alternate Bearing
--- Financial Perspective
Fluctuations in Quality
Small, poorly filled nuts
Premature germination
Shuck decline
Average In-Shell Pecan Price
1992-2009
Instability of cash flow
‘On’ Years
$0.89/lb
‘Off’ Years
$1.17/lb
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
Off On Off On Off On
Off On Off
On Off
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
Why does it occur?
Management:
Best varieties
Smaller nuts
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
Mahan
0.74
Moneymaker
0.68
San Saba
0.85
Schley
0.60
Stuart
0.47
Western Schley
0.56
Wichita
0.67
(best)
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
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
What about next year?
Edited by: Vincent Mannino,
County Extension Director – Fort Bend