Or­chard Man­age­ment

The Orchardist - - Contents - By John Wil­ton

An early sea­son

The only thing cer­tain about fruit grow­ing is that each year will be dif­fer­ent.

My gen­eral im­pres­sion is that at the end of the first week in Novem­ber the sea­son was run­ning about 10 days ahead of nor­mal with re­gard to fruit de­vel­op­ment. Grow­ing de­gree days (GDDs) base 10°C ac­cu­mu­lated from the be­gin­ning of Septem­ber con­firm this opin­ion. When this sea­son is bench­marked against Gis­borne, our ear­li­est ap­ple har­vest dis­trict, our spring tem­per­a­tures in Hawke’s Bay have been very close to a nor­mal good Gis­borne spring. This means that there is a fair chance that Royal Gala, for in­stance, will be ready for har­vest early to mid Fe­bru­ary rather than mid to late Fe­bru­ary. Fruit size and length of time from full bloom to har­vest is mainly driven by the tem­per­a­tures ex­pe­ri­enced over the cell di­vi­sion pe­riod, and the crop load. There are strong re­la­tion­ships be­tween the GDDs base 10°C ac­cu­mu­lated over the first 50 days and both fruit size po­ten­tial and har­vest time ex­pressed as days af­ter full bloom (DAFB) for ap­ples.

Early fruit thin­ning is also a crit­i­cal part in max­imis­ing har­vestable yield, fruit size, fruit colour de­vel­op­ment, fruit pres­sure and fruit dry mat­ter.

With our good spring tem­per­a­tures this sea­son, con­di­tions have also been ideal for chem­i­cal thin­ners to work. Veg­e­ta­tive growth has also been lush this spring, due to the good grow­ing con­di­tions giv­ing good chem­i­cal thin­ner up­take, and the nec­es­sary com­pe­ti­tion be­tween shoot growth and fruit to give strong nat­u­ral fruit drop – which has of­ten been en­hanced a bit too much by the chem­i­cal thin­ners. Con­se­quently, there are a few thin crops about. If it con­tin­ues to be a warm sea­son, bet­ter make sure ro­bust cal­cium pro­grammes are ap­plied to va­ri­eties that are prone to pit and blotch.

In some va­ri­eties, I have seen early nat­u­ral fruit drop bring fruit­set to ones and twos, as well as many cleared sites with­out the help of any blos­som pe­riod thin­ning sprays.

Pol­li­na­tion ef­fects

The im­pact of poor pro­vi­sion for cross-pol­li­na­tion in ap­ples is more marked this sea­son than usual.

The va­ri­eties most af­fected are Brae­burn, which this year had a very early short flow­er­ing pe­riod, and Scired which is 100% self-in­fer­tile and in the ab­sence of dor­mancy break­ers to bring its blos­som pe­riod for­ward, flow­ered when most other va­ri­eties were fin­ished.

This is a good year to as­sess whether your or­chard has suf­fi­cient pro­vi­sion for cross-pol­li­na­tion. In re­cent years there has been a trend to plant or­chards in­ten­sively in large sin­gle va­ri­ety blocks. Af­ter two or three grow­ing sea­sons, trees in the row tend to grow into one another. Once this be­gins to hap­pen bees travel along the rows rather than across rows, so your pollinators need to be in the rows for good fruit­set.

A few years ago, be­fore we be­gan to in­ten­sify ap­ple or­chards and move into large scale pro­duc­tion units, it was tra­di­tional to plant va­ri­eties in four to six row blocks. The main rea­son for this prac­tice was to take care of the cross-pol­li­na­tion re­quire­ment.

Six rows was gen­er­ally con­sid­ered about as wide as you could go be­fore run­ning into fruit­set prob­lems due to poor crosspol­li­na­tion. In lo­ca­tions with high den­si­ties of or­chards, it was pos­si­ble to get sat­is­fac­tory fruit­set in larger plant­ings of sin­gle va­ri­eties. This ef­fect was thought to be due mainly to pollen mix­ing in the hives through some of the hive work­ing other va­ri­eties.

In small, iso­lated or­chards, pro­vi­sion for cross-pol­li­na­tion is much more crit­i­cal, and I think we are reach­ing this sit­u­a­tion

in our main dis­tricts now due to the pre­dom­i­nance of large sin­gle va­ri­ety plant­ings.

I am also of the opin­ion that many diploid ap­ple va­ri­eties have some mea­sure of self-fer­til­ity if flower is strong, such as the “on” crop, and tem­per­a­tures over the pol­li­na­tion pe­riod are very good.

In the “off” crop year, which for many Brae­burn blocks is this sea­son, flower is too weak to be­come self-pol­li­nated, but will read­ily set if there is good cross-pol­li­na­tion.

In­ci­den­tally, if there is not good pro­vi­sion for cross-pol­li­na­tion, bring­ing more bees in is not go­ing to help much.

Im­me­di­ately prior to hand thin­ning is a good time to as­sess pol­li­na­tion.This is eas­ily done and the two things to check are:

1 Any fall-off in fruit­set den­sity as dis­tance from other

va­ri­eties in­creases.

2 Seed num­bers in the fruit.

As a gen­eral rule the first three or four rows ad­ja­cent to other va­ri­eties show good fruit­set, then as you move fur­ther across the block the fruit be­gins to dis­ap­pear. In­ci­den­tally, the min­i­mum dif­fer­ence you can see by eye is about 20%, so if you are see­ing vis­ual dif­fer­ences it is more than that.

With bi­en­nial va­ri­eties, it is not un­usual for the rows ad­ja­cent to the next va­ri­ety, or the pol­li­na­tor row, to be­come vi­o­lently bi­en­nial. For this rea­son, you need to bench­mark your fruit­set

through the block against the set in rows three or four from the block bound­ary.

There is also high bee traf­fic along the ends of the rows, so in the ab­sence of bi­en­nial bear­ing, fruit­set on the end of row trees is usu­ally ex­ces­sive. Your pol­li­na­tion as­sess­ments need to be made a few trees into the block. Ex­pe­ri­ence with fruit­set lev­els in iso­lated or­chards in­di­cates that sin­gle tree or branch pol­li­na­tor in­flu­ence ex­tends about 10 to 15 me­tres down the row. This means that ded­i­cated pol­li­na­tor trees need to be 20 to 30 me­tres apart for ap­ples. In­ci­den­tally, I re­mem­ber see­ing a Red De­li­cious or­chard in the Bay of Plenty which had the root­stock grow­ing in­stead of the scion va­ri­ety in one cor­ner of the plant­ing. The only trees that cropped in that or­chard were the ones around the flow­er­ing root­stock. I saw a sim­i­lar thing once with Brae­burn. In this case there was a very large Malus pro­fu­sion in the grower’s gar­den. The Brae­burn trees cropped heav­ily and were quite stunted due to crop load for the first 30 odd me­tres into the block, then nor­mal canopy size and good crop­ping per­for­mance in the 30 to 60 me­tre dis­tance zone from the M pro­fu­sion tree, then be­yond that ex­cess vigour and no crop. The ap­ple flower has five locules, each with two ovules, giv­ing a fully pol­li­nated po­ten­tial of 10 seeds per fruit. For fruit­set it is not es­sen­tial for all ovules to be pol­li­nated, but in my opin­ion you need at least five, prefer­ably uni­formly dis­trib­uted around the locules.With strong flower and good cross-pol­li­na­tion the num­ber of seeds is more likely to be in the 7 to 10 range. You need this num­ber for good fruit shape and to cap­ture the fruit’s full po­ten­tial size. If your fruit cut­ting regime is con­sis­tently show­ing less than four or five de­vel­op­ing seeds per fruit, this is a sure sign of a pol­li­na­tion prob­lem.

Some va­ri­eties, no­tably Royal Gala types, will abort seeds dur­ing the grow­ing sea­son and in some years there will be no vi­able seeds near har­vest. While we do not fully un­der­stand this phe­nom­e­non, this seed abor­tion prob­lem is quite dif­fer­ent to lack of ini­tial pol­li­na­tion when the seeds do not grow at all.

Other im­pacts on crop man­age­ment from The early sea­son

If the favourable grow­ing con­di­tions con­tinue, it is likely that fruit size is go­ing to be larger than has been seen in the last two or three grow­ing sea­sons.

Where fruit num­bers and dis­tri­bu­tion al­low, and you have good out­lets for smaller fruit sizes, crop loads in high red

long-stemmed va­ri­eties could be in­creased a lit­tle by leav­ing a few more twos and threes in the bunches.

I sus­pect, how­ever, that some blocks will not have enough crop to al­low this. In th­ese blocks, there will need to be care­ful crop as­sess­ment to de­ter­mine if it is worth spend­ing money on ex­pen­sive hand thin­ning.

In large-fruited, par­tial red va­ri­eties such as the Pa­cific se­ries, Scilate and Fuji, dili­gent hand thin­ning is still nec­es­sary. Th­ese va­ri­eties need to be sin­gled and spaced out ir­re­spec­tive of crop load if you want to achieve a smooth har­vest, high pack­outs, and pick at op­ti­mum ma­tu­rity to give good out-turn in the mar­ket­place.

The early sea­son, lighter crops and larger fruit sizes has the po­ten­tial to give over­ma­tu­rity prob­lems if the har­vest is not well-man­aged, and the fruit is not picked on time.Th­ese are the con­di­tions that lead to fruit ma­tu­rity rac­ing away if you are not ready for har­vest.

If your har­vest labour sup­ply will not ar­rive in time for an early har­vest, con­sid­er­a­tion needs to be given to de­lay­ing ma­tu­rity strate­gies for Royal Gala. The in­dus­try has es­tab­lished a rep­u­ta­tion in the mar­ket­place for a high qual­ity, crisp and juicy Royal Gala which is sell­ing at a pre­mium to com­peti­tor fruit. Do not de­stroy this progress by ship­ping large vol­umes of over-ma­ture prod­uct this sea­son be­cause the har­vest was not or­gan­ised on time.

Mon­i­tor fruit siz­ing progress

To­wards the end of Oc­to­ber I was for­tu­nate to at­tend the Hawke’s Bay Sum­mer Green meet­ing at which Pro­fes­sor Luca Corelli Grap­padelli, a tree fruit spe­cial­ist from the Univer­sity of Bologna, spoke on or­chard per­for­mance.

Pro­fes­sor Corelli’s opin­ion was that fruit growth and fruit size were the best pa­ram­e­ters to mea­sure when as­sess­ing tree per­for­mance.

“Over-ma­ture fruit which lacks crunch and good flavour does not go down well in the mar­ket and if too much over­ma­ture fruit gets through, all the good work in es­tab­lish­ing our Royal Gala as a pre­mium prod­uct will be lost.”

With good data on fruit size and fruit growth rates, it is pos­si­ble to pre­dict fruit size dis­tri­bu­tion at har­vest, which is a great help when or­gan­is­ing pack­ag­ing and mar­ket­ing strate­gies. Another point that he made was that for our cli­mate, based on data from the in­ter­na­tional ap­ple tree per­for­mance study led by Dr Stuart Tustin, we have about 55 days from full bloom to bring ap­ple crop loads down into the op­ti­mum crop load for max­i­mum fruit size re­sponse from hand thin­ning. For this sea­son, 55 days from full bloom would be about the be­gin­ning of De­cem­ber.

Ag­First’s Or­chardNet pro­gramme has a fruit siz­ing tool which can be used to track the progress of your fruit size. His­tor­i­cal data on fruit siz­ing in­di­cates that Royal Gala fruit siz­ing be­tween 30 days and 90 days af­ter full bloom (DAFB) falls within the range of 4 to 4.5mm per week. Af­ter 90 DAFB there is a steady fall off in fruit siz­ing, down to about 3mm per week at 112 DAFB, con­tin­u­ing to fall to 2mm per week at about 140 DAFB, with fur­ther de­cline to un­der 1.5mm per week at around 150 DAFB.

Where trees are un­der stress through crop load or wa­ter stress, the down­ward trend in fruit siz­ing from about 90 DAFB, usu­ally early Jan­uary, will be much steeper.

By about 50 DAFB it is pos­si­ble to ob­serve fruit dif­fer­ences for sim­i­lar aged fruit emerg­ing. For in­stance, at this stage 110 count fruit should have been 32mm and 100 count fruit 35mm in di­am­e­ter. At 95 DAFB 100 count fruit should be 60mm, and 110 count fruit 57mm in di­am­e­ter. Af­ter about 50 DAFB, the fruit size hi­er­ar­chy among the fruits on the tree has be­come es­tab­lished, so it is pos­si­ble to size thin with con­fi­dence to re­move lower value small fruit. As fruitlets will grow at around 4mm per week un­til late De­cem­ber or early Jan­uary, it is nec­es­sary to ad­just min­i­mum fruit sizes to thin to twice a week.

If crop loads are ex­ces­sive and fruit siz­ing shows signs of stop­ping around 90 DAFB, fruit growth can be started by a re-thin, re­mov­ing smaller or dam­aged fruits to bring the crop down to what the tree can han­dle. With late thin­ning, sun­burn can be an is­sue, par­tic­u­larly where it is nec­es­sary to break up bunches and ex­pose hith­erto shaded fruit to di­rect sun.

de­laY­ing haR­vesT

In the case of Royal Gala, par­tic­u­larly the high red strains, ap­pli­ca­tion of Re­tain be­fore any ripen­ing be­gins can give 10 to 14 days de­lay in har­vest ma­tu­rity. Over the last cou­ple of sea­sons Re­tain has been par­tic­u­larly ef­fec­tive, with har­vest de­lay of 14 or more days quite com­mon.

Th­ese sea­sons were quite cool over the pre-har­vest and har­vest pe­riod for Royal Gala.The in­ci­dence of sun­burned fruit in Royal Gala crops was rel­a­tively low and I think the ab­sence of sun­burn con­trib­uted to the ef­fec­tive­ness of Re­tain be­cause sun­burn in­jured fruit trig­gers the re­lease of en­doge­nous eth­yl­ene in the crop, which re­duces the ef­fec­tive­ness of Re­tain. In nor­mal sea­sons, Re­tain ap­pli­ca­tion in Royal Gala is made about the last week in Jan­uary. As this sea­son is run­ning early, op­ti­mum Re­tain tim­ing will also be ear­lier this sea­son, maybe even mid Jan­uary.

In early va­ri­eties check­ing for ma­tu­rity move­ment needs to com­mence 10 to 14 days ear­lier than nor­mal.

In­ci­den­tally, a large pro­por­tion of our Royal Gala are high colour strain on dwarf root­stocks, which can have high starch con­tent. Be­cause starch con­cen­tra­tions are high, ma­tu­rity can be more ad­vanced than the starch io­dine test would in­di­cate. If sol­u­ble solids (Brix) read­ings are start­ing to lift and there is no in­di­ca­tion of the starch io­dine pat­terns mov­ing, the starch pat­tern will go fast once it be­gins to move, so you had bet­ter be ready to har­vest. If it ap­pears that fruit ma­tu­rity will be ahead of your har­vest labour sup­ply, bet­ter con­sider us­ing Re­tain to hold the fruit back to im­prove your chances of har­vest­ing it at op­ti­mum ex­port ma­tu­rity.

John Wil­ton is a de­cid­u­ous fruit spe­cial­ist, Ag­First

In re­cent sea­sons New Zealand Royal Gala has com­manded a pre­mium in the mar­ket­place due to good colour en­abling the crop to be har­vested at op­ti­mum ex­port ma­tu­rity. All the point­ers we have in­di­cate that this will be an early har­vest sea­son. Over-ma­ture fruit which lacks crunch and good flavour does not go down well in the mar­ket and if too much over-ma­ture fruit gets through, all the good work in es­tab­lish­ing our Royal Gala as a pre­mium prod­uct will be lost.

Fig­ure 1. Chem­i­cal thin­ning sprays worked very well this year, as the den­sity of th­ese dropped Beurre Bosc fruitlets shows. The block was thinned with Ben­zy­lade­nine at the equiv­a­lent of 900 g/100 l con­cen­tra­tion.

Fig­ure 2. The Beurre Bosc fruit­set af­ter fruit thin­ning. Fig­ure 3. Brae­burn fruit­set where cross-pol­li­na­tion was good three to four rows dis­tant from the pol­li­na­tor va­ri­ety. Fig­ure 4. Poor Brae­burn fruit­set in the mid­dle of the block.

Fig­ure 5. Hawke’s Bay av­er­age weekly fruit siz­ing ex­pressed as DAFB for the 2012/13 sea­son. Fig­ure 6. Hawke’s Bay av­er­age weekly fruit siz­ing by cal­en­dar date for the 2012/13 sea­son. The small dif­fer­ences be­tween this curve and that of the DAFB curve is d

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