Orchard Management Fine tuning the crop
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
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™
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.
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.
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.
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.