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: Who’s Guilty?
Nuts
Temperate
Fruits
Sub-Tropical
Tropical
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
‘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
Off On
Off On
Off On
Off On
Off On
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. Alternate Bearing Intensity (I)
Why does it occur?
Cultivar
Alternate Bearing Intensity (I)
Barton
0.36
Bradley
0.56
Burkett
0.29
Cape Fear
0.53
Cherokee
(worst)
Desirable
0.40
Elliot
0.68
Gloria Grande
(best)
Mahan
0.74
Moneymaker
San Saba
0.85
Schley
0.60
Stuart
0.47
Western Schley
Wichita
0.67
Management:
Best varieties
Smaller nuts

13. How do we stop it? Insect Control Disease 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. Edited by: Vincent Mannino, County Extension Director – Fort Bend
What about next year? ?
Edited by: Vincent Mannino,
County Extension Director – Fort Bend