To net or not to net - 3rd edition - Department of Primary Industries

Case study 9—tunnel netting on lychee (coathanger frame
system)
A North Queensland Tai So orchard planted on a 9 m x 7 m spacing.
The frames are made from an arc of metal hoop mounted on 75 mm
square galvanised metal posts placed 28 m apart. The posts are 8 m
high to allow for the vigorous growth of trees in North Queensland’s
climate (Figure 66).
The net is rolled out over the hoops from a cherry picker. The net is
stored each year on a polypipe roll, which fits on a frame attached
to the cherry picker. The net rolls off the frame as the cherry picker
operator rolls the net out over the canopy. The nets are simply
pinned to the ground every couple of metres using homemade wire
tent pegs.
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The net controls birds and bats and prevents FPM damage to
a significant extent.
A significant advantage of the metal structure is that it is
termite-proof.
Case study 10—full canopy hail netting on stone fruit
A 4 ha, low-chill stone fruit orchard in northern New South Wales.
White, diamond mesh hail net with double cross-stitch on the
canopy and black bird net with 25 mm mesh on all sides. The net is
seven years old and looks to be in good general condition. The net
is expected to last at least another three years. The canopy is 5.5 m
above the ground.
External posts are CCA-treated pine with an SED of 30 cm. Each
post is anchored to a buried log deadman with stay wires. There is a
main cable every 14 m, which is the same width as the net, and an
intermediate cable every 14 m (alternating with the main cables) to
give extra support. There are intermediate cables every 28 m at right
angles to the main cable run. The intermediate cables and main
cable form a 7 m x 28 m grid. The main cables are six-strand wires
and the intermediate cables are four-strand. The internal poles are
offset along each main cable every 28 m, forming a square diamond
with a 28 m axis.
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Doors are kept closed even during the off-season.
On the headlands the side nets are bevelled at 45 degrees
to give room for machinery to turn easily. On the other two
sides the nets are vertical.
Significant wear of net on cable joints where the intermediate
cables are strung between end posts (Figure 67) is a problem
but the holes do not ‘run’.
Grower does not have any particular concerns regarding
delays in fruit maturity or quality.
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To net or not to net
Figure 66. An all-metal
coathanger tunnel frame
Case study 11—full canopy hail netting on stone fruit
White hail net over a 3.5 ha, low-chill stone fruit orchard in northern New South Wales.
Figure 67. Rub tears occur on
any irregular shape such as this
eyelet
The canopy is 6 m high and the posts are 1 m in the ground. The net was installed by a contractor for
$1.70/m 2 . This included all the cables and the net, which is worth $0.68/m 2 . Locally purchased hardwood
poles (bloodwood and north coast stringy) with a minimum SED of 200 mm were used for posts. These
were oiled three times with old engine oil before erecting. Headlands are 10 m wide to give ample room
for turning tractors and machinery. The structure and net are rated W44 for wind resistance.