2 Effect of Shading on Pecan Trees Sunlight is the most limiting factor in most Georgia pecan orchardsNut production is limited by the trees’ ability to absorb solar radiationIntensifies alternate bearing and results in poor quality during the “on” year
3 Sunlight: When to thin the orchard? Thin trees when 60% of orchard floor is shadedUsually between years for young orchardsTrees PlantedNeed Canopies less thanDriplines should be:35X3528 ft diameter7 ft apart40X4032 ft diameter8 ft apart50X5040 ft diameter10 ft apart60X6048 ft diameter12 ft apart70X7056 ft diameter14 ft apart
5 Trees within an orchard vary Wood (1989) selected 21 ‘Stuart’ trees about 80-years-old at random from a Georgia orchard and kept up with yields of individual trees for 6 years.The best tree averaged 328 lbs. per year, the worst tree averaged 26 lbs., a 12-fold difference.12 of the 21 trees were “superior”, that is they were above average both in yield and regularity of bearing.
6 Steps to Selective Thinning Make an orchard mapShould indicate cultivar and size of treesScore each individual tree.Score reflects tree condition, yield, andcultivar preference. We use 1-10 scale30St7
7 Not selectively thinned Selectively thinned twice
8 After Thinning49% of area covered by canopies.Before Thinning84% of area covered by canopies.
9 Yields from a selectively thinned orchard. ---Bill Goff YearU.S. CropLb./acre1998Off942About 50% of trees cut down this winter by selective tree removal1999On17062000Off136545% increase from previous off-year2001On15712002Off12875 yr. average of 1432 through 2 thinnings, with no year less than 1200 lbs.About 45% of trees cut down2003On1231
10 Alternate bearing is affected by when you thin. If you thin before an ‘on’ year, alternate bearing is reducedIf you thin before an ‘off’ year, alternate bearing is increased.
11 Shuck Split on October 5, 2007 a a b a a a Bars with different letters indicate a significant difference at P<0.05
12 Shuck Split by Tree Side abData Taken from trees with at least 1 adjacent tree removed
13 2007 Pecan Prices $320/Acre loss* Price = In-Shell Price for 49-51% Desirable (USDA)*Based on 1000 lbs/A
20 Keys to Spading Pecan Trees Prune back according to tree size4-5” diameter: very little pruning required15” diameter: top at 16’, leave 3 limbs cut back to 4’Water, Water, Water
21 Fruit ThinningRemoving fruit from the tree prior to floral induction (mid July-early August)Improves return cropIncreases current season qualitySome cultivars respond better than others
22 Fruit Thinning of Pecan Evaluate crop load around July 4Toward mid-late July begin cutting nutsWhen ovule development is ½ way, it is time to thin
23 Fruit Thinning of Pecan Lubricate pads with silicon gelGrab tree/limb at center of padShake for 3 seconds and check
24 When and How Much to Thin? Nut SizeExampleOptimum Crop Load>70/lbElliott60-70%50-70/lbCape Fear, Stuart50-60%<50/lbOconee45-50%
25 Characteristics of Pecan Cross pollinated cropSimilar to peopleTakes two to make a seedSeedlings are different from the parent and each other
26 Seedling trees have diverse nut size, Seedling Vs. CultivarPecans may be either grafted cultivars or seedlings.Cultivar = VarietySeedling trees have diverse nut size,nut shape, andkernel quality.
27 Type I and Type II Pecans Type I (protandrous)-pollen matures before pistil is receptive(Desirable, Oconee, Cape Fear)Type II (protogynous)-pistil matures before pollen(Stuart, Sumner, Elliott)Timing of flower maturity may change with time for a particular varietyFlower maturity occurs earlier and for shorter durations in older trees
30 Providing Sufficient Pollination Fruit set declines with distance from pollinatorIn off year, yield may be as much as 30% less on trees more than 2 rows (80’) from pollinatorPollinator should be placed no more than 150’ from main variety