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Summer girdling – current options and new ideas
Mike Currie and Richard Jackman, HortResearch - Mt Albert, Shane Max - ZESPRI
Peter Blattmann, HortResearch - Te Puke, Shona Seymour, HortResearch - Nelson
Although summer (February) trunk girdling is an easy and effective
way to increase dry matter, it may not suit all orchards. February
cane girdling can also be effective and different timings of girdling
may suit some orchards. Here we review results from a range of
trials and describe how growers can run their own trials.
2007 TRIALS IN WHANGAREI AND NELSON
In 2006, ZESPRI were fi elding reports that trunk girdling was not
effective in some regions such as Whangarei and Nelson. To
determine if there was any evidence to support this, trials were set
up with two Hayward orchards in each of these regions (Figure 1).
In Nelson, the practice of summer cane girdling was also included,
as some orchardists in the region had reported that this was as
effective on their vines (Figure 2).
It was clear that in most of the sites, there was an acceptable
response to trunk girdling. For example, at Whangarei orchard 1, dry
matter was increased by over one percent - unit. This would
translate to a lift in Taste ZESPRI Grade (TZG) of c. 0.15 units.
Alongside this was an impressive gain of c. 8 g of fruit weight. We
estimated that this sort of response would have lifted production at
this orchard by c. 800 trays/ha and orchard returns by c. $8,000/
ha (ZESPRI Canopy website OGR calculator). Fruit at both Nelson
orchards also responded fairly well to trunk girdling plus showed
some response to cane girdling. This suggests that Nelson growers
are correct that summer cane girdling is effective, although our
results suggest that trunk girdling would be more effective for them,
as long as vines were healthy.
At one of the Whangarei sites, there was no response to trunk
girdling at all, for either dry matter or fruit weight. This is the fi rst
time that we have recorded a nil response to trunk girdling in a
replicated trial ever and demonstrates that the technique cannot be
guaranteed to work every single time! In some ways, we are not
altogether surprised. Responses to girdles applied to Katikati
orchards have often been better than in Te Puke orchards in our
trials. Although we cannot fully explain these differences, there is a
range of possibilities that could explain why trunk girdling can
appear to have been less effective in some situations, such as:
• Vines were different to start with. This can often be the case
when individual blocks or maturity areas are compared with
one another. However, with randomisation and replication
Figure 1. HortResearch’s Richard Jackman applying a trunk girdle at a
Whangarei orchard in 2006.
Figure 2. A new cane girdle applied in February at a Nelson Hayward orchard.
Note the healed spring cane girdle on the left hand side.
procedures used in research trials this is less likely. In our case,
we had actually collected a sample of fruit at the start of the
experiment in February that confi rmed that the two sets of vines
had been initially very similar
NZ KIWIFRUIT JOURNAL JANUARY / FEBRUARY 2008
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