00:05 Harvest labour can be difficult to get. Harvest with ladders is dangerous and inefficient
use of labour. The productivity of a worker walking up and down ladders is reduced by
30% compared to pickers standing on the ground. Platform picking is used in intensive orchard
systems like stone fruit and apples. Robotic harvesting is being developed for smaller
orchard canopies. Citrus orchards with smaller trees are a real possibility in the future,
and growers must plan for this.
00:38 Trials are underway in Australia to evaluate new dwarfing citrus rootstocks. Currently
Flying Dragon is the only dwarfing stock available.
00:48 Mature trees are almost two metres tall, and it takes too long to reach this size.
00:55 In the 1980s, a dwarfing viroid was used at Yanco in semi-commercial plantings
planted at high densities and inoculated with a mild strain dwarfing viroid. These Valencia
blocks attained 40 tonnes per hectare in year four.
01:10 As you can see, 35 years later, these are still some of the best blocks on our research
stations. Yields plateau and have consistently yielded between 55 and 60 tonnes per hectare
for the last 30 years.
01:28 These are Washington navel on dry 22 stock. You can see the grower has planted
at high density and has efficiently used the dwarfing viroid to limit mature tree height.
01:41 Fruit internal quality is not affected nor is the size of the fruit.
01:48 For over 30 years, Harrison Produce has effectively used the dwarfing viroid to
manage the vigour of citrus trees on their orchards. This is a 12-year-old natural Salustiana
on trifoliate stock, and it is standing five metres tall. The rest of the trees are viroid
dwarf and stand 2.6 metres tall.
02:15 Growers whom have natural Salustiana a hedging heavily or pruning every year to
manage the canopy. And they also experience lower yields. These Salustiana were inoculated
with the dwarfing viroid 18 months after planting. Trees grow naturally for six years until the
dwarfing viroid kicks in. By planting higher densities and effectively using the viroid,
Allen has managed to maintain yields in excess of 60 tonnes per hectare without the expense
of pruning.
02:50 Make sure you use budwood from a certified source like our citrus. If you add a dwarfing
viroid to a tree which already contains other viroids, you may have problems.
03:02 The right time to inoculate a tree with a viroids varies with the sign vigour and
the desired mature tree height. Look carefully at the row on the left. Inoculation 12 months
after planting was ideal for Salustiana in this high density planting.
03:21 Decades of New South Wales DPI research looked at the impact of the dwarfing viroid
before recommending it for commercial use with navel and Valencia oranges on trifoliate,
Troyer and Carrizo citrange rootstocks.
03:36 Ideal growing conditions and management are important when using the dwarfing viroid,
especially the suitability of the rootstock to the soil conditioners.
03:47 If you plant in a cut soil type area, expect smaller trees in the poor soil structure
regardless of the viroid.
03:55 If a young orchard experience prolong dry soil moisture, stress, expect smaller
trees.
04:03 Similarly, in a citrus replant situation, expect smaller trees regardless of the dwarfing
viroid or not.
04:12 The viroid can be spread from inoculated to normal trees on cutting tools when crooning
hedging or budding. Sterilise all blades used on dwarf trees before using them on non-inoculated
trees. With good planning and management, the dwarfing viroid can increase productivity
and profitability of citrus orchards.
04:32 Further information on viroid dwarfing can be found on the New South Wales DPI website.