Prun­ing for the best out of av­o­ca­dos

A num­ber of grow­ers are fac­ing the daunt­ing task of prun­ing as their av­o­cado trees grow to un­man­age­able heights caus­ing lack of light in the or­chard, de­clin­ing pro­duc­tion and in­creas­ing costs.

The Orchardist - - Contents - By Erica Faber, Or­chard Pro­duc­tiv­ity Man­ager, Just Av­o­ca­dos Ltd

Prun­ing to man­age these is­sues is an es­sen­tial prac­tice that should take place for the en­tire life of the trees. If done cor­rectly, and in a sim­ple uni­form way, it can im­prove or­chard pro­duc­tiv­ity, tree per­for­mance, and or­chard man­age­ment.

In the early years of the tree’s life, prun­ing is aimed at ma­nip­u­lat­ing growth for an im­proved fruit bear­ing struc­ture that will achieve op­ti­mum yield. In later years, and with un­pruned trees show­ing de­cline, the em­pha­sis shifts to pro­mot­ing re­ju­ve­na­tion and en­sur­ing max­i­mum sun­light to pen­e­trate the tree canopy.

IS­SUES WITH UN­PRUNED TREES

As trees grow taller and denser, the lower and in­te­rior limbs lose their abil­ity to pro­duce fruit be­cause of in­creased shad­ing. Over time, most fruit will be pro­duced on the outer pe­riph­ery of the tree pri­mar­ily at the top, as this is ex­posed to the most sun­light. Un­for­tu­nately, the top of the tree is also where the most wind dam­age, sun­burn, and poorer qual­ity fruit oc­curs as spray pen­e­tra­tion to these heights can be less ef­fec­tive.

The cost of man­ag­ing and har­vest­ing un­pruned trees pro­por­tion­ally in­creases with the tree height, re­sult­ing in smaller re­turns.

TYPES OF PRUN­ING

There are pre­dom­i­nately two types of prun­ing – head­ing cuts / tip­ping and thin­ning.

Head­ing cuts or tip­ping re­moves the grow­ing point thereby break­ing api­cal dom­i­nance and stim­u­lat­ing lat­eral bud break and branch­ing.

Thin­ning is used to in­crease light pen­e­tra­tion by re­mov­ing com­pet­ing or crowd­ing shoots or limbs.

Ad­van­tages of reg­u­lar prun­ing: • Im­proved light dis­tri­bu­tion into the canopy which is

es­sen­tial for flower bud de­vel­op­ment, fruit set and growth. • Im­proved bear­ing struc­ture which in­creases pro­duc­tion

po­ten­tial and en­cour­ages reg­u­lar crops. • Growth of new shoots with high qual­ity flower buds. • Bet­ter spray pen­e­tra­tion and there­fore im­proved pest

con­trol. • Bet­ter air move­ment through­out the canopy, im­prov­ing dry­ing con­di­tions and re­duc­ing the sever­ity of fun­gal dis­eases. • Suc­cess­ful re­growth of dis­eased or dam­aged wood.

CON­SIS­TENCY IS KEY

There are many ap­proaches to and opin­ions on prun­ing be­ing dis­cussed in the in­dus­try. Whichever ap­proach you de­cide to ap­ply, en­sure that you re­main con­sis­tent and ap­ply it to each tree so that the re­sul­tant light pen­e­tra­tion within the tree and or­chard is uni­form.

In or­der to de­ter­mine what ap­proach to take when prun­ing, first ask your­self what you are try­ing to achieve and what you need to do to get the tree to re­spond ac­cord­ingly. De­pend­ing on the tree age, size and plant­ing den­sity your ap­proach will vary. You also need to un­der­stand the plant phys­i­ol­ogy and de­vel­op­ment

and how it responds to dif­fer­ent types of prun­ing

It must also be re­mem­bered that when prun­ing off a branch, the pro­duc­tion of that branch is lost, ei­ther by prun­ing off the ex­ist­ing fruit, the flow­ers or the po­ten­tial flow­ers. The eco­nomic loss in the long run, will be the same re­gard­less of whether you can see the fruit or not. The pres­ence of fruit there­fore, should not in­flu­ence where the prun­ing cut should be.

POST PRUN­ING MAN­AGE­MENT

Man­ag­ing the prun­ings, newly ex­posed branches within the tree, and the re­growth is es­sen­tial to en­sur­ing that prun­ing ef­forts will be ef­fec­tive and

worth­while.

Sun­burn on ex­posed branches and new prun­ing cuts as well as sec­ondary rots and cankers can cause ir­repara­ble dam­age af­fect­ing tree health, per­for­mance and yield.

To pro­tect the ex­posed limbs and prun­ing cuts against sun­burn, a mix­ture of white acrylic paint, wa­ter and cop­per oxy­chlo­ride can ei­ther be painted or sprayed on.

Prun­ings left un­der the tree can sig­nif­i­cantly in­crease the in­ocu­lum lev­els of fun­gal dis­eases, thereby in­creas­ing the in­ci­dence of an­thrac­nose and post-har­vest rots. How­ever, once chipped, the mulch spread evenly un­der the tree from the dripline to the trunk be­comes a valu­able re­source im­prov­ing root health, soil mi­cro­bi­ol­ogy, wa­ter holding ca­pac­ity, and weed sup­pres­sion.

“Thin re­growth to min­imise com­pe­ti­tion for light and re­sources and en­able stronger and more pro­duc­tive re­growth.”

Fi­nally, man­age­ment of prun­ing re­growth is es­sen­tial at an early stage. Thin re­growth to min­imise com­pe­ti­tion for light and re­sources and en­able stronger and more pro­duc­tive re­growth. Tip re­growth to break api­cal dom­i­nance and en­cour­age lat­eral branch­ing for op­ti­mal pro­duc­tion.

Re­ju­ve­nat­ing large trees with prun­ing will im­prove light dis­tri­bu­tion into the canopy which is es­sen­tial for flower bud de­vel­op­ment, fruit set and growth.

As trees grow taller and denser, the lower and in­te­rior limbs lose their abil­ity to pro­duce fruit be­cause of in­creased shad­ing.

Thin­ning opens the in­te­rior to light and air, and de­fines the struc­ture of the plant. When thin­ning, a com­bi­na­tion of cuts can be used. Thin­ning or

lat­eral cut

Head­ing re­duce over­all size and en­cour­ages new plant growth.

Head­ing cuts

Thin­ning re­growth is es­sen­tial to min­imise com­pe­ti­tion for light and re­sources.

Pro­tect ex­posed limbs and prun­ing cuts against sun­burn by ap­ply­ing a mix­ture of white acrylic paint, wa­ter and cop­per oxy­chlo­ride.

Tip re­growth to break api­cal dom­i­nance and en­cour­age lat­eral branch­ing for op­ti­mal pro­duc­tion. Newly ex­posed branches are vul­ner­a­ble to sun­burn which can cause ir­repara­ble dam­age af­fect­ing tree health, per­for­mance and yield.

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