Or­chard Man­age­ment Fine tun­ing the crop

The Orchardist - - Contents - By John Wil­ton

The pe­riod be­tween now and Christ­mas is very im­por­tant for setting up the or­chard for an easy har­vest sea­son and en­sur­ing a good re­turn bloom for the next crop.

This spring, apart from those af­fected by wa­ter log­ging, I did not see too many or­chards with­out full crop po­ten­tial, even among bi­en­nial bear­ing va­ri­eties.

By now the re­sults of the chem­i­cal thin­ning pro­gramme should be vis­i­ble and hand thin­ning pro­grammes should be get­ting un­der­way. Ex­pe­ri­ence has shown that ir­re­spec­tive of how good a job the chem­i­cal thin­ning pro­gramme has done, it is gen­er­ally nec­es­sary for some hand thin­ning. If hand thin­ning is not nec­es­sary, this is a sig­nal that fruit­set was in­ad­e­quate or the chem­i­cal thin­ning has been too ag­gres­sive. Once the ini­tial fruit drop has fin­ished, it is a very good time to as­sess crop load and for­mu­late a hand thin­ning strat­egy.

Blos­som pe­ri­ods were com­pressed this spring which will have favoured good chem­i­cal thin­ner re­sponse be­cause of the high lev­els of in­ter fruit com­pe­ti­tion. Also, be­cause the blos­som pe­riod was com­pressed the tree will have had less op­por­tu­nity to com­pen­sate for a re­duc­ing fruit­set by setting more of the late flower fruit which of­ten hap­pens when blos­som pe­ri­ods were stretched out. need for cross pol­li­na­tion. When we used to plant mixed va­ri­ety or­chards with four to six row va­ri­ety blocks, suf­fi­cient cross pol­li­na­tion oc­curred to set good crops with­out the need for spe­cific pol­li­na­tors. This is not the case once large

blocks of a sin­gle va­ri­ety are planted.

Since then plant­ings have moved to hedge rows rather than in­di­vid­ual trees so most bee move­ment in the or­chard is now along row rather than across rows. Add a hail net over the top and cross row bee move­ment is fur­ther re­stricted.

Ob­ser­va­tions I have made in iso­lated or­chards is that in­flu­ence of a sin­gle small canopy vol­ume of a pol­li­na­tor along a row is around 15 me­tres for ap­ples but for pears I have seen pol­li­na­tor in­flu­ence only ex­tend­ing around three to five me­tres.

Where there are large quan­ti­ties of other va­ri­ety pollen avail­able, the fruit­set in­flu­ence into a block can ex­tend 40 to 50 me­tres be­fore fruit­set drops be­low ad­e­quate lev­els. Check pol­li­na­tion by ob­serv­ing the den­sity of fruit­set and con­firm it by cut­ting fruitlets to check seed num­bers. It is gen­er­ally con­sid­ered that for good fruit qual­ity and shape there needs to be at least four to six vi­able seed evenly dis­trib­uted around the fruit. Where there are fewer seeds or the seeds are con­fined only to one side of the fruit, the fruit is likely to be

mis­shaped.

RE­VIEW DRAINAGE

Poor fruit­set and heavy fruit drops are of­ten as­so­ci­ated with soil wa­ter log­ging over flow­er­ing and fruit­set pe­riod. This year in many or­chards we mon­i­tored soil mois­ture lev­els around flow­er­ing time to de­ter­mine how wa­ter logged soils were. We found a large pro­por­tion of the sites we checked were clearly wa­ter logged be­low about 30cm depth, even though we had had well un­der half the nor­mal Septem­ber rain­fall. Last year in Hawke’s Bay Septem­ber was very wet with more

than twice the nor­mal rain­fall for the month and this re­sulted in some or­chards shed­ding their crops. Al­though we did not have the high Septem­ber rain­fall this sea­son, soil mois­ture lev­els were prob­a­bly sim­i­lar to last spring.

Also in re­gard to soil wa­ter log­ging, we are ob­serv­ing nu­mer­ous in­stances of phy­to­tox­i­c­ity from oil or dor­mancy breaker ap­pli­ca­tions where these prod­ucts have been ap­plied to trees with stressed roots due to wet soils. Cli­mate change seems to be chang­ing rain­fall pat­terns which along with soil com­paction prob­lems caused by pas­sage of heavy ma­chin­ery dur­ing spray­ing and har­vest, is ac­cen­tu­at­ing drainage and root health prob­lems.

In re­cent years, we have seen ex­pan­sion of or­chard crops onto prop­er­ties that were pre­vi­ously used for an­nual sum­mer crops. There is a large dif­fer­ence in the level of drainage that was ad­e­quate for an­nual crops and that nec­es­sary for per­ma­nent tree crops. The lat­ter needs deep drainage, prefer­ably down to a me­tre to main­tain a ro­bust healthy root sys­tem.

Trees with deep, healthy root sys­tems are also much more re­silient to draught and re­quire much less ir­ri­ga­tion than those with shal­low root sys­tems. Now that we are in­ten­si­fy­ing our or­chards and push­ing the yield and fruit qual­ity pa­ram­e­ters higher and higher, main­tain­ing healthy root sys­tems through­out the year is be­com­ing crit­i­cal to or­chard per­for­mance.

THE HAND THIN­NING PRO­GRAMME

Thin­ning is the most im­por­tant crop hus­bandry task in the or­chard. To main­tain ad­e­quate fruit re­turns, our crops have to be tar­geted at the top end of the mar­ket. This re­quires blem­ish free fruit, high fruit colour, good pack­out uni­for­mity, cou­pled with su­perb taste and crisp­ness. A tall or­der when you con­sider the haz­ards fruit has to go through be­tween flower and con­sumer. The thin­ning pro­gramme is key to achiev­ing this ob­jec­tive.

The ma­jor­ity of our va­ri­eties, par­tic­u­larly the pre­mium ones, need thin­ning to spaced sin­gles for high pack­outs of top grade fruit. It is gen­er­ally not pos­si­ble to achieve this re­sult from a sin­gle thin­ning pass. One of the rea­sons for this is that we have only lim­ited time for the first pass of hand thin­ning if we want to max­imise the ben­e­fit in re­gard to fruit size and re­turn bloom. Try­ing to do a pre­cise job in re­gard to fruit spac­ing and po­si­tion­ing fruit tends to slow up the job so the first thin­ning pass will ex­tend into the hot weather pe­riod when sun­burn can be­come a prob­lem.

PLAN­NING THIN­NING PRI­OR­I­TIES

Be­fore thin­ning be­gins, it is nec­es­sary to have de­fined crop load tar­gets, then carry out fruit site counts to de­ter­mine the prethin­ning crop load level present. This will iden­tify the crop load lev­els by block and va­ri­ety and pro­vide some base data for setting thin­ning pri­or­i­ties.

Bunchy crops, par­tic­u­larly in those va­ri­eties with short stems usu­ally need to be thinned first be­cause once fruit siz­ing be­gins to close the bunches, hand thin­ning be­comes much more dif­fi­cult. These va­ri­eties in­clude Scifresh, Fuji, Smit­ten™

and Brae­burn.

Va­ri­eties prone to bi­en­nial bear­ing will crop more reg­u­larly if thin­ning can be done within four to six weeks of flow­er­ing. For­tu­nately, bi­en­nial bear­ing ap­pears to be less of a prob­lem these days than it was, un­doubt­edly due to more ef­fec­tive chem­i­cal thin­ning tools and the use of sum­mer NAA

pro­grammes to lift re­turn bloom lev­els.

Mar­ket re­quire­ments need recog­ni­tion too when plan­ning hand thin­ning strate­gies. If ad­vanc­ing har­vest is a key ob­jec­tive for early va­ri­eties, crop loads need to be con­ser­va­tive. Some va­ri­eties such as Scired, Smit­ten™, Scilate, Sciearly and Fuji pay large pre­mi­ums for high colour and larger fruit sizes. Early thin­ning, with for the later va­ri­eties a fur­ther thin­ning to bring them down to spaced sin­gles is the way to max­imise fruit value. The name of the game with these va­ri­eties is to grow value, not tonnes.

In re­cent years, we have seen a trend to­wards late har­vested va­ri­eties, which along with de­te­ri­o­rat­ing har­vest weather is plac­ing more and more pres­sure on our abil­ity to har­vest the crop in tip top con­di­tion. Ease of har­vest is de­ter­mined by how good the hand thin­ning has been done. A well thinned crop to spaced sin­gles in these pre­mium va­ri­eties ad­vances colour de­vel­op­ment, as well as in­creas­ing the level of colour around the fruit by elim­i­nat­ing within bunch shad­ing. These crops are easy to har­vest and be­cause of the pre­mi­ums paid for large, high colour fruit, the lower yields caused by drop­ping fruit num­bers to achieve spaced sin­gles is likely to be re­cov­ered in bet­ter fruit value.

SETTING CROP LOADS

The key to high pro­duc­tion of top qual­ity fruit lies in setting up uni­form crops. In young trees, fruit per cm² trunk cross sec­tional area (TCA) is a very ac­cu­rate way of setting yield po­ten­tial. Young trees grow­ing well with no ob­vi­ous lim­it­ing fac­tors can carry fruit num­bers in the 10 to 12 fruit per cm² TCA with­out ad­verse ef­fects on tree de­vel­op­ment. In­ci­den­tally, for young trees un­der stress it is gen­er­ally the flower load that does the dam­age rather than the fruitlets that set so by the time you get around to strip­ping the set fruit off them most of the dam­age to tree growth has al­ready been done.

Once trees fill their al­lot­ted space, fruit load per cm² TCA loses its rel­e­vance. Setting crop loads by branch cross sec­tional area (BCA) is a much more ac­cu­rate way of setting up crop loads. Branch units in the re­gion of 2 to 2.5cm in di­am­e­ter should be thinned down to about four fruit per cm² BCA, ie 13 to 20 fruitlets. As branch di­am­e­ter in­creases, op­ti­mum crop loads fall away. At 3.5 to 4cm di­am­e­ter, there should be only three fruit per cm² BCA, ie 29 to 38 fruit. Be­fore thin­ning, it is a good idea to do some fruit site counts to de­ter­mine what level of hand thin­ning will be re­quired. If fruit­ing site num­bers fall well short of the num­ber re­quired for a good crop in sin­gles, it may be nec­es­sary to leave a few dou­bles in favoured sites.

IN­STRUCT, SU­PER­VISE AND MON­I­TOR

Fruit thin­ners need clear in­struc­tions that are sim­ple and eas­ily un­der­stood by them. Where fruit site num­bers are ad­e­quate, the in­struc­tion should be “thin to sin­gles”. In the first pass with rel­a­tively un­skilled thin­ners, do not try to get them to space pre­cisely be­cause this may slow progress too much. For va­ri­eties which need good colour and size, sin­gles are best so do not be tempted to leave mul­ti­ples. With in­ex­pe­ri­enced peo­ple once you al­low them to leave more than sin­gles, you run the risk of hav­ing the whole crop in mul­ti­ples un­less very ex­plicit in­struc­tions are given as to where more than one fruit in the bunch can be left, eg only tip buds.

Ex­pe­ri­ence has shown that where more than two or three ex­pe­ri­enced thin­ners are used there will be a range of

“The key to high pro­duc­tion of top qual­ity fruit lies in setting up uni­form crops.”

dif­fer­ent thin­ning lev­els among the gang. As you can only read­ily pick up a min­i­mum of about 20% vari­a­tion by eye, it is nec­es­sary to count fruitlets to de­ter­mine the qual­ity of the thin­ning job. Once you break the mon­i­tor­ing job down to sim­ple branch units, count­ing be­comes very easy and can be done quickly. For this pur­pose, there is no need to count whole trees which can take a lot of time.

At the com­mence­ment of thin­ning a block, a few trees should be care­fully thinned to show the thin­ners how the com­peted job should look. This is part of their train­ing.

While branch counts should be the ba­sis of your mon­i­tor­ing pro­gramme, it is nec­es­sary to do a few whole tree counts to make sure fruit num­bers are close to where they need to be.

FRUIT­SET VARI­ABLE

Even though flow­er­ing ap­peared to be fairly uni­form across most blocks this spring, large dif­fer­ences in fruit­set are ap­pear­ing due to the ef­fects of wa­ter log­ging on tree health. Where root sys­tems have been dam­aged there has been very high lev­els of nat­u­ral drop, even in the ab­sence of chem­i­cal thin­ning sprays.

These crops will be dif­fi­cult to hand thin well and usu­ally in this sit­u­a­tion the heav­ier set trees are sel­dom thinned hard enough. Weak, stunted trees in par­tic­u­lar, usu­ally set ex­ces­sive crop loads and need sig­nif­i­cantly more hand thin­ning than higher vigour trees in the block.

It is also dif­fi­cult to thin such blocks on per tree con­tract rates and achieve a sat­is­fac­tory thin­ning job be­cause heavy set trees will bog down the thin­ners which means they will try to race over them. Hourly or row rates may be a bet­ter ap­proach to take. If you set row rates be pre­pared to get the thin­ner to re-thin the heavy set parts of the row if they have not been thinned well enough.

THIN­NING BRUISES

Once fruitlets gain a bit of size they will bruise fruit if they are dropped down through the tree. Each year when we look at pack­house re­ject anal­y­sis sheets, the old bruise cat­e­gory which is largely thin­ning and wind­fall bruises is around 1% of the to­tal crop but in bad lines can be 5% or more of the crop.

Make sure the thin­ners are not drop­ping fruitlets down through the tree. Some­times there is a pro­cess­ing out­let for thin­nings to make acid juice. With thee ris­ing pop­u­lar­ity of cider, de­mand for this prod­uct should be lift­ing. Where this out­let is avail­able, sell­ing thin­nings can sub­stan­tially re­duce the net cost of hand thin­ning.

SUN­BURN

Once we run into hot weather in mid to late De­cem­ber, there is a high risk of sun­burn to bunched ap­ples which have been thinned dur­ing hot weather. This prob­lem can be greatly re­duced if the va­ri­eties that need in­ten­sive hand thin­ning can be brought down to sin­gles be­fore the hot weather ar­rives. Once the crop is in sin­gles fur­ther fruit thin­ning and crop grooming can be done with­out much sun­burn risk.

In­ci­den­tally, in re­gard to sun­burn, we have ob­served that heavy crop trees suf­fer more prob­lems that trees with lower crop lev­els.

From left: Fig 1. The Royal Gala have set an ad­e­quate crop where the soil is less wa­ter logged than those in fig­ure 2. Fig 2. Fruit­set is poor on these trees. They have suf­fered from poor drainage, are in the wet­ter area of the same block as the tree in fig­ure 1.

From top: Fig 3. This Fuji tree on MM116 is show­ing de­layed bud break and tip dieback symp­toms. This is typ­i­cal of many Fuji grow­ing on wet soils that have been sprayed with dor­mancy break­ers, fol­lowed by oil sprays. Fig 4. This un-thinned branch shows a

From top: Fig 5. These Scilate have been dili­gently thinned to sin­gles in the first thin­ning pass. There is still too many fruit so a sec­ond thin­ning to space fruit will be re­quired. Fig 6. These Scilate are thinned to well spaced sin­gles. Note the greate

Fig 7. Im­pact of branch di­am­e­ter on fruit num­ber per cm² BCA.

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