<table border=0 cellpadding=2 cellspacing="0"><tr><td>
<pre>I am a little puzzled by the mysteries of alternate bearing. As I have only
been planting olives over the past 5 years I have not been witness to this
phenomena taking place within my own grove.
Am I right in assuming that no matter which year the trees are planted they
eventually fall into some form of synchronised pattern and the whole grove
alternates between 'on' and 'off' years. Presumably this occurs on a
district or regional basis.
What governs the beginning of this pattern and at what age does it manifest
itself in the trees?
Are there any management practices such as pruning and irrigation regimes
that may alleviate the highs and lows of production?
Alan Watt,
Tanja Olives


[Non-text portions of this message have been removed]
</pre>
</td></tr></table>

<table border=0 cellpadding=2 cellspacing="0"><tr><td>
<pre>Most tree crops including apples, (olives are now to be espically
bad) are alternate bearing naturally due to a combination of
carbohydrate levels (i.e high draw in on year results in low reserves
for the following fruiting season), hormone levels caused by the
presence of fruit late in the season in olives also seems to have an
effect on the trees ability to set the following crop. Management
practices such as prunning and fruit thinning after flowering in an on
year can reduce the trees demand. Irrigation and other managment
practics will also reduce the difference between requirments
between demand and supply. Ensuring fruit are not harvested to
late in the season will also reduce biennial bearing.
The season and variety will also have a considerable effect, in
modern irrigated groves with regular prunning etc it should not be to
bad? But some one with a mature modern grove can probably
confirm that. (not many here in NZ)

Iain
</pre>
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<pre>Briefly alternate bearing is a phenomenon that occurs with most fruit
trees. A simple explanation is that while the tree is bearing fruit all
resources are being directed to that function and less are directed to
the production of new wood that will provide fruit the next season. The
converse occurs in the next season becaise of the light fruit load the
tree produces more new wood and hence a large crop will follow.

From my experience - some varieties are more prone to alternate bearing.
For those varieties that fruit early in the season - the tree can catch
up and so the alternate bearing is less pronounced. eg Manzanillo and
Koroneiki have less pronounced alternate bearing than Gordal Sevillano.

Regarding - strategies to overcome alternate bearing - pruning,
nutrition, water will help but small and large crops still occur. With
table olives - if thinning of fruit is practiced then in the off year
thinning may not be necessary.

Thinning out of fruit appears to be a USA phenomenon but practiced less
elswhere.

Stan
</pre>
</td></tr></table>

<table border=0 cellpadding=2 cellspacing="0"><tr><td>
<pre>Alan:

Here is a California perspective on alternate bearing (i.e. what happens
here). In my view for California, its one of the most serious phenomenon
that effect grower profitability in a table fruit industry (probably a big
problem for oil too).

As you know, heavy crops are invariably followed by lighter ones (alternate
or biennial bearing). First, you need to remember that olives are, for all
practical purposes, borne on one-year-old shoots (i.e. grown the previous
season) of modest vigor (not those excessively vigorous and not those of
little vigor) - for the California Manzanillo shoots 8" - 16" long are most
fruitful. In the year of the heavy crop, shoot growth that will bear the
subsequent crop is physically depressed - without fruitful shoots, no crop
will occur the following year. The degree of depression depends on the
cropping level and your management of it through the growing season
(thinning, pruning, irrigating, etc.). Management can, should be tailored to
crop size to maximize shoot growth early each season.

A further effect of large crops on alternate bearing is their late maturity
(heavy crops mature later than light ones - oil accumulation as well).
Allowing a crop to remain on the tree late into the winter to attain
profitable size (in the table industry) or maximiize oil content is a
considerable drain on carbohydrate reserves that would otherwise go to
flower bud differentiation and development. Bloom is seriously depressed the
subsequent year when harvest is delayed for long periods.

Other, more external factors that initiate alternate bearing are weather or
disease events that directly reduce bloom and/or crop or defoliate reducing
bloom development. For example, late Spring frost kills developing buds so
that a light crop results throwing the tree into alternation. Cold weather
during the bloom development period reduces effective bloom; the result is a
light crop that will be followed by a heavy one. Excessive heat and/or
drying winds on a sensitive Cv's open bloom (e.g. California Manzanillo)
reduces pollination and crop - again throwing the tree into an alternate
condition. In my opinion, the reason a region seems to alternate together is
that a weather event that had a broad influence over a large area starts it
off. Finally, allowing the trees to defoliate due to disease (e.g. peacock
spot), or be nutritionally deficient will reduce bloom and start the cycle.

As you can see, some things are under the growers control and some are not.
However when natural events (weather) decimate a crop, careful management of
the subsequent heavy crop (e.g. modifying crop load) are required to avoid
alternation and poor profitability in subsequent years. It should be noted
that the leaf-to-fruit ratio is what mostly effects shoot growth, flower
initiation, differentiation and subsequent cropping. Thus fruit thinning, as
practiced by table fruit growers here, reduces fruit load without reducing
leaves - improves the leaf-to-fruit ratio for the remainder of the season.
This is the most effective. Pruning, on the other hand, reduces both leaves
and fruit so its primary effect is to promote new shoot growth that will
hopefully bear the next year. For the table industry, both are used as
management practices to stabilize cropping.

Hope this helps.

Steve Sibbett
U.C. Farm Advisor
Phone - office 559.733.6486
Mobil 559.280.0666
FAX 559.734.2708

-----Original Message-----
From: Alan Watt [mailto:wattmeyer@one.net.au]
Sent: Thursday, November 02, 2000 3:17 PM
To: OliveOil@egroups. com
Subject: [OliveOil] Alternate bearing


I am a little puzzled by the mysteries of alternate bearing. As I have only
been planting olives over the past 5 years I have not been witness to this
phenomena taking place within my own grove.
Am I right in assuming that no matter which year the trees are planted they
eventually fall into some form of synchronised pattern and the whole grove
alternates between 'on' and 'off' years. Presumably this occurs on a
district or regional basis.
What governs the beginning of this pattern and at what age does it manifest
itself in the trees?
Are there any management practices such as pruning and irrigation regimes
that may alleviate the highs and lows of production?
Alan Watt,
Tanja Olives


[Non-text portions of this message have been removed]



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</pre>
</td></tr></table>

<table border=0 cellpadding=2 cellspacing="0"><tr><td>
<pre>It is complicated.

Firstly pruning helps to reduce the differences. I have seen
unpruned trees here swing from almost zero crop to heavy crops over a
couple of years.

Secondly a major weather event such as a frost or drought can put
all the trees into the same phase.

Thirdly a look at the Italian district averages shows that large
differences occur but not on a simple year on year off basis.

For Umbria the yields were as follows: 1985 - 500 kg/ha 1986 - 590
kg/ha 1987 - 1070 kg/ha 1988 - 880 kg/ha

while in next door Toscana the sequence was 650 kg, 360 kg. 780 kg
580 kg

The 1986 crop followed the severe frost of 1985 but I cannot find a
simple pattern.

Cheers Brian Chatterton


[Non-text portions of this message have been removed]
</pre>
</td></tr></table>

<table border=0 cellpadding=2 cellspacing="0"><tr><td>
<pre>Talking as a real novice, is it possible to thin say half the branches one year,
and thinning the unthinned branches the following year reduce the on year/off
year bearing?

Steve Sibbett wrote:

> Alan:
>
> Here is a California perspective on alternate bearing (i.e. what happens
> here). In my view for California, its one of the most serious phenomenon
> that effect grower profitability in a table fruit industry (probably a big
> problem for oil too).
>
> As you know, heavy crops are invariably followed by lighter ones (alternate
> or biennial bearing). First, you need to remember that olives are, for all
> practical purposes, borne on one-year-old shoots (i.e. grown the previous
> season) of modest vigor (not those excessively vigorous and not those of
> little vigor) - for the California Manzanillo shoots 8" - 16" long are most
> fruitful. In the year of the heavy crop, shoot growth that will bear the
> subsequent crop is physically depressed - without fruitful shoots, no crop
> will occur the following year. The degree of depression depends on the
> cropping level and your management of it through the growing season
> (thinning, pruning, irrigating, etc.). Management can, should be tailored to
> crop size to maximize shoot growth early each season.
>
> A further effect of large crops on alternate bearing is their late maturity
> (heavy crops mature later than light ones - oil accumulation as well).
> Allowing a crop to remain on the tree late into the winter to attain
> profitable size (in the table industry) or maximiize oil content is a
> considerable drain on carbohydrate reserves that would otherwise go to
> flower bud differentiation and development. Bloom is seriously depressed the
> subsequent year when harvest is delayed for long periods.
>
> Other, more external factors that initiate alternate bearing are weather or
> disease events that directly reduce bloom and/or crop or defoliate reducing
> bloom development. For example, late Spring frost kills developing buds so
> that a light crop results throwing the tree into alternation. Cold weather
> during the bloom development period reduces effective bloom; the result is a
> light crop that will be followed by a heavy one. Excessive heat and/or
> drying winds on a sensitive Cv's open bloom (e.g. California Manzanillo)
> reduces pollination and crop - again throwing the tree into an alternate
> condition. In my opinion, the reason a region seems to alternate together is
> that a weather event that had a broad influence over a large area starts it
> off. Finally, allowing the trees to defoliate due to disease (e.g. peacock
> spot), or be nutritionally deficient will reduce bloom and start the cycle.
>
> As you can see, some things are under the growers control and some are not.
> However when natural events (weather) decimate a crop, careful management of
> the subsequent heavy crop (e.g. modifying crop load) are required to avoid
> alternation and poor profitability in subsequent years. It should be noted
> that the leaf-to-fruit ratio is what mostly effects shoot growth, flower
> initiation, differentiation and subsequent cropping. Thus fruit thinning, as
> practiced by table fruit growers here, reduces fruit load without reducing
> leaves - improves the leaf-to-fruit ratio for the remainder of the season.
> This is the most effective. Pruning, on the other hand, reduces both leaves
> and fruit so its primary effect is to promote new shoot growth that will
> hopefully bear the next year. For the table industry, both are used as
> management practices to stabilize cropping.
>
> Hope this helps.
>
> Steve Sibbett
> U.C. Farm Advisor
> Phone - office 559.733.6486
> Mobil 559.280.0666
> FAX 559.734.2708
>
> -----Original Message-----
> From: Alan Watt [mailto:wattmeyer@one.net.au]
> Sent: Thursday, November 02, 2000 3:17 PM
> To: OliveOil@egroups. com
> Subject: [OliveOil] Alternate bearing
>
> I am a little puzzled by the mysteries of alternate bearing. As I have only
> been planting olives over the past 5 years I have not been witness to this
> phenomena taking place within my own grove.
> Am I right in assuming that no matter which year the trees are planted they
> eventually fall into some form of synchronised pattern and the whole grove
> alternates between 'on' and 'off' years. Presumably this occurs on a
> district or regional basis.
> What governs the beginning of this pattern and at what age does it manifest
> itself in the trees?
> Are there any management practices such as pruning and irrigation regimes
> that may alleviate the highs and lows of production?
> Alan Watt,
> Tanja Olives
>
> [Non-text portions of this message have been removed]
>
> ************************************************** ***
> Addresses:
> Post message: OliveOil@egroups.com
> Subscribe: OliveOil-subscribe@egroups.com
> Unsubscribe: OliveOil-unsubscribe@egroups.com
> List owner: OliveOil-owner@egroups.com
> URL to this page: http://www.egroups.com/group/OliveOil
>
>
> ************************************************** ***
> Addresses:
> Post message: OliveOil@egroups.com
> Subscribe: OliveOil-subscribe@egroups.com
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</pre>
</td></tr></table>

<table border=0 cellpadding=2 cellspacing="0"><tr><td>
<pre>This is a commonly asked question (often growers talk about managing every
other tree by fruit thinning or pruning to even out the crops - thus 1/2 the
orchard in "on" and the other "off" hopefully reversing the following year -
this would have more effect than within tree branch thinning). The problem
with this scenario is weather. If there is some broad weather event (dry hot
winds during bloom, frost or freeze etc.) that eliminates the crop on the
branches or trees left to fruit then the crop is lost in the entire orchard
one year and 1/2 the orchard the previous year. Further, extremely heavy
crops can be expected following the weather event year, aggravating biennial
bearing if the crop is left un-managed (lack of operating money etc.).
Finally, relative to your scenario if fruit size is important, an excessive
crop on certain limbs in the tree will result in reduced fruit size and late
maturity (the leaf:fruit ratio is not improved) on those limbs.

In my opinion, one is much wiser to manage the crop in the entire orchard
each year (e.g. pruning during bloom development when the bloom can be
evaluated and pruning severity adjusted and/or fruit thinning - not as
popular) according to the crop's size.

Steve Sibbett
U.C. Farm Advisor
Phone - office 559.733.6486
Mobil 559.280.0666
FAX 559.734.2708

-----Original Message-----
From: Trudy Hollinshead [mailto:hollinshead@olis.net.au]
Sent: Monday, November 06, 2000 3:48 AM
To: OliveOil@egroups.com
Subject: Re: [OliveOil] Alternate bearing


Talking as a real novice, is it possible to thin say half the branches one
year,
and thinning the unthinned branches the following year reduce the on
year/off
year bearing?

Steve Sibbett wrote:

> Alan:
>
> Here is a California perspective on alternate bearing (i.e. what happens
> here). In my view for California, its one of the most serious phenomenon
> that effect grower profitability in a table fruit industry (probably a big
> problem for oil too).
>
> As you know, heavy crops are invariably followed by lighter ones
(alternate
> or biennial bearing). First, you need to remember that olives are, for all
> practical purposes, borne on one-year-old shoots (i.e. grown the previous
> season) of modest vigor (not those excessively vigorous and not those of
> little vigor) - for the California Manzanillo shoots 8" - 16" long are
most
> fruitful. In the year of the heavy crop, shoot growth that will bear the
> subsequent crop is physically depressed - without fruitful shoots, no crop
> will occur the following year. The degree of depression depends on the
> cropping level and your management of it through the growing season
> (thinning, pruning, irrigating, etc.). Management can, should be tailored
to
> crop size to maximize shoot growth early each season.
>
> A further effect of large crops on alternate bearing is their late
maturity
> (heavy crops mature later than light ones - oil accumulation as well).
> Allowing a crop to remain on the tree late into the winter to attain
> profitable size (in the table industry) or maximiize oil content is a
> considerable drain on carbohydrate reserves that would otherwise go to
> flower bud differentiation and development. Bloom is seriously depressed
the
> subsequent year when harvest is delayed for long periods.
>
> Other, more external factors that initiate alternate bearing are weather
or
> disease events that directly reduce bloom and/or crop or defoliate
reducing
> bloom development. For example, late Spring frost kills developing buds so
> that a light crop results throwing the tree into alternation. Cold weather
> during the bloom development period reduces effective bloom; the result is
a
> light crop that will be followed by a heavy one. Excessive heat and/or
> drying winds on a sensitive Cv's open bloom (e.g. California Manzanillo)
> reduces pollination and crop - again throwing the tree into an alternate
> condition. In my opinion, the reason a region seems to alternate together
is
> that a weather event that had a broad influence over a large area starts
it
> off. Finally, allowing the trees to defoliate due to disease (e.g. peacock
> spot), or be nutritionally deficient will reduce bloom and start the
cycle.
>
> As you can see, some things are under the growers control and some are
not.
> However when natural events (weather) decimate a crop, careful management
of
> the subsequent heavy crop (e.g. modifying crop load) are required to avoid
> alternation and poor profitability in subsequent years. It should be noted
> that the leaf-to-fruit ratio is what mostly effects shoot growth, flower
> initiation, differentiation and subsequent cropping. Thus fruit thinning,
as
> practiced by table fruit growers here, reduces fruit load without reducing
> leaves - improves the leaf-to-fruit ratio for the remainder of the season.
> This is the most effective. Pruning, on the other hand, reduces both
leaves
> and fruit so its primary effect is to promote new shoot growth that will
> hopefully bear the next year. For the table industry, both are used as
> management practices to stabilize cropping.
>
> Hope this helps.
>
> Steve Sibbett
> U.C. Farm Advisor
> Phone - office 559.733.6486
> Mobil 559.280.0666
> FAX 559.734.2708
>
> -----Original Message-----
> From: Alan Watt [mailto:wattmeyer@one.net.au]
> Sent: Thursday, November 02, 2000 3:17 PM
> To: OliveOil@egroups. com
> Subject: [OliveOil] Alternate bearing
>
> I am a little puzzled by the mysteries of alternate bearing. As I have
only
> been planting olives over the past 5 years I have not been witness to this
> phenomena taking place within my own grove.
> Am I right in assuming that no matter which year the trees are planted
they
> eventually fall into some form of synchronised pattern and the whole grove
> alternates between 'on' and 'off' years. Presumably this occurs on a
> district or regional basis.
> What governs the beginning of this pattern and at what age does it
manifest
> itself in the trees?
> Are there any management practices such as pruning and irrigation regimes
> that may alleviate the highs and lows of production?
> Alan Watt,
> Tanja Olives
>
> [Non-text portions of this message have been removed]
>
> ************************************************** ***
> Addresses:
> Post message: OliveOil@egroups.com
> Subscribe: OliveOil-subscribe@egroups.com
> Unsubscribe: OliveOil-unsubscribe@egroups.com
> List owner: OliveOil-owner@egroups.com
> URL to this page: http://www.egroups.com/group/OliveOil
>
>
> ************************************************** ***
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> Subscribe: OliveOil-subscribe@egroups.com
> Unsubscribe: OliveOil-unsubscribe@egroups.com
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</pre>
</td></tr></table>

<table border=0 cellpadding=2 cellspacing="0"><tr><td>
<pre>I have seen an olive grove of 400+ grafted Verdale trees about 40 years
old where half bear one year, half the next. The present owner did not
plant the trees but assumes that the planting time was staggered. The
fact that despite the various environmental influences on the grove the
bearing pattern still exists is a mystery. The owner thinks its a good
system as his income is constant over the years (ie not much over the years!)

Roger Farquhar

[Non-text portions of this message have been removed]
</pre>
</td></tr></table>

<table border=0 cellpadding=2 cellspacing="0"><tr><td>
<pre>I have seen an olive grove of 400+ grafted Verdale trees about 40 years
old where half bear one year, half the next. The present owner did not
plant the trees but assumes that the planting time was staggered. The
fact that despite the various environmental influences on the grove the
bearing pattern still exists is a mystery. The owner thinks its a good
system as his income is constant over the years (ie not much over the years!)

Roger Farquhar

[Non-text portions of this message have been removed]
</pre>
</td></tr></table>