Alternate Bearing Research -Implications for Western Pecans- :Alternate Bearing Research -Implications for Western Pecans-


What is Alternate Bearing? :What is Alternate Bearing? Alternate Bearing- the tendency for wide cyclical swings in yield ‘On’ and ‘Off’ years. Related terms: Biennial bearing, irregular bearing, masting.


Slide 3:Source: Monselise and Goldschmidt, 1982 Alternate Bearing: Who’s Guilty?


What does alternate bearing look like? :What does alternate bearing look like? Alternate Bearing Intensity (I) I = 0.07 I = 0.27 I = 0.21 Where n is the number of years and a1, a2, an-1 and an are yield of corresponding years


How are CA pecans doing? :How are CA pecans doing? I = 0.34 I = 0.23


How are CA pecans doing? :How are CA pecans doing? I = 0.34 I = 0.23 I = 0.17


Is Alternate Bearing Bad? First an Ecological Perspective :Is Alternate Bearing Bad? First an Ecological Perspective Alternate bearing in the wild: Oak, beech, pine, elm, hickory Reproductive advantage: Pest suppression.


The Horticultural Perspective- Is Alternate Bearing a Bad Thing? :The Horticultural Perspective- Is Alternate Bearing a Bad Thing? It Hurts Every Level of the Pecan Industry! Pecan growers Instability of cash flow Freeze damage Limb breakage Tree “collapse” Pecan processors and contract harvesters Facilities/equipment run below capacity in ‘Off’ years.


Alternate Bearing Hurts Pecan Markets :Alternate Bearing Hurts Pecan Markets Fluctuations in Quality Small, poorly filled nuts Premature germination Shuck decline Fluctuations in Price


What makes the trees alternate? :What makes the trees alternate? Yield (lbs/acre)


What makes the trees alternate? :What makes the trees alternate? Yield (lbs/acre) Fruits per Acre Flowers per Acre Percentage Fruit Set (%) *


What makes the trees alternate bear? :What makes the trees alternate bear? Yield (lbs/acre) Fruits per Acre Flowers per Acre Percentage Fruit Set (%) *


Why are there fewer flowers after an ‘On’ year? :Why are there fewer flowers after an ‘On’ year? Fewer flowering sites in the canopy olive, prune, pecan. Direct inhibition of floral induction apple, pear, hazelnut, prune, citrus, pecan. Source: Wetzstein and Sparks, 1986


Direct inhibition of flower bud initiation :Direct inhibition of flower bud initiation Spring ‘06 Summer ‘06 Fall ‘06 Winter ‘06/’07 Spring ‘07 Summer ‘07 Floral Induction/Differentiation Fruit/Kernel Growth Bloom Bloom Harvest


Direct inhibition of flower bud initiation :Spring ‘06 Summer ‘06 Fall ‘06 Winter ‘06/’07 Spring ‘07 Summer ‘07 Floral Induction/Differentiation Fruit/Kernel Growth Bloom Bloom Harvest Current season fruit/seed growth and induction/ differentiation of next year’s flowers overlap. Direct inhibition of flower bud initiation


Management: Start with the right varieties :Management: Start with the right varieties Source: Conner and Worley, 2000 http://aggie-horticulture.tamu.edu/carya/ Traits Associated with Alternate Bearing: Fruit size Fruit setting potential Post-harvest foliation period?


Management: Fruit Thinning :Management: Fruit Thinning Chemical thinning??? Currently no chemical-thinners are registered for pecan NAA and Ethephon have shown some promise Mechanical thinning Potential trunk damage. “Pecan Crop Load Management” http://www.osuextra.com Source: McGraw, Smith and Reid


Management: What Fruit Thinning did for the Apple Industry :1949 U.S. apple production, 1935-1973. Apple growers began using chemical fruit thinners around 1949. Management: What Fruit Thinning did for the Apple Industry


Management: When to thin. :Management: When to thin. Fruiting terminals (%) Pistillate flowers per cluster Julian date of defruiting Source: Wood, 1995 cv ‘Cheyenne’ It is critical to thin before kernel fill (before “Dough Stage”) 50-100% ovule expansion. Source: McGraw et al


Management: Pruning :Management: Pruning Light management. Removes flower buds- THINNING! Source: Wood and Stahmann, 2004 Hedging/topping 2 year cycle Hedging/topping 8 year cycle


Management: Avoid “triggering events” :Management: Avoid “triggering events” Severe infestations of nut-eating insects Late frosts Hail storms Trigger (e.g. Hail) On On On On On On Off Off Off Off Off Off


Promote leaf health all the way to the end of the season. :Promote leaf health all the way to the end of the season. Aphid control Late-season irrigation Zinc nutrition Nitrogen nutrition ‘On’ vs ‘Off’ year rates? Late season application? Source: entoplp.okstate.edu