Mechanically box-pruned Pinot
Grigio had 72% higher yields, with
13% smaller berry size. This was due
to a significantly greater number of
shoots per foot.
Mechanically shoot-thinned treatments
significantly affected yields. In
both varieties, the high shoot density
treatment had significantly higher
yields. Although there were no differences
in yield in the low and medium
shoot density treatments in Syrah, the
high shoot density treatment had 12%
more yield. In Pinot Grigio, the yield
increased significantly with each
increase in shoot density treatment.
Interactions – There were no effects
of dormant pruning method, shoot
density control, or leaf removal on the
leaf area to fruit ratio of Syrah vines.
This was probably due to the vigorous
growth habit of Syrah, where
long shoots with large leaves usually
make up for the removal of shoots by
Shoot density and leaf removal interacted
to affect the leaf area to fruit ratio
of Pinot Grigio. High shoot density
treatments with leaf removal did not
have enough leaf area for the amount
of fruit that was borne on the shoots.
Conversely, vines receiving low shoot
density treatments with no leaf removal
had excess leaf area for the amount of
fruit that was borne on the shoots.
Effect of canopy management on
fruit composition – Hand spur-pruned
Syrah vines reached the 24° Brix target
one week prior to mechanically boxpruned
During ripening, Syrah vines with
low and medium shoot density treatments
had higher Brix than those
with high shoot density treatment.
However, by 24° Brix, there was no
difference among the three shoot density
treatments. Leaf removal did not
affect harvest date.
The hand spur-pruned Pinot Grigio
vines had higher total soluble solids
throughout ripening, compared
to mechanically box-pruned vines,
and reached 22° Brix two weeks earlier.
Pinot Grigio vines with low and
medium shoot density treatments were
harvested two weeks prior to those
with high shoot density. Leaf removal
delayed harvest of Pinot Grigio vines
by one week.
Take Home messages
Mechanical pruning is not enough
to control yield.
vines did not give adequate
control of the shoot number
and production, because the
Figure 2. Shoot thinning was applied to Pinot Grigio vines using an Oxbo Cordon Brush
(Model 62731) with auxiliary shoot-thinning heads. This cordon brush was mounted to an
Oxbo 1210 single-row tractor-mounted tool carrier.
of non-count shoots was equal to or
more than the number of count shoots
retained at pruning. Although noncount
shoots are not as fruitful, they
are likely the cause of overcropping,
and cannot be controlled by pruning.
Mechanical shoot-thinning is
needed to adequately control yield.
Without accurate shoot thinning, there
is potential for excessive yields. The
ability to mechanically reduce the number
of non-count shoots makes achieving
vine balance possible through
mechanized farming practices.
When vines were mechanically
shoot-thinned, the medium shoot density
treatment resulted in optimum
shoot density for these cultivars: 7 and
10 count shoots per foot for Syrah and
Pinot Grigio, respectively.
Mechanical shoot-thinning techniques
can be improved. For example,
the total numbers of shoots retained
were different than the intended treatments
for count shoot control.
The three shoot density treatments
called for 7, 10, and 15 count shoots
per foot and the actual numbers were
12, 13, and 17 total shoots per foot for
Syrah, and 17, 20, and 21 total shoots
per foot for Pinot Grigio (very difficult
to thoroughly thin on a 12-inch
Integrating at least two canopy management
practices ensures improvement
of the canopy microclimate.
Pruning alone does not adequately
control canopy microclimate for either
cultivar. For Syrah, integrating pruning,
shoot density, and leaf removal
ensures fewer leaf layers.
Leaf removal as a stand-alone practice
improves PPFD and percent canopy
gaps for Syrah. For Pinot Grigio,
a combination of dormant pruning
and shoot-thinning, or leaf removal
as a stand-alone treatment, improves
PPFD transmittance or percent canopy
gaps. Leaf removal was the only treatment
to effectively control the leaf
layer numbers for Pinot Grigio.