A mysterious and growing scourge of Queensland sugarcane is prompting some long time canegrowers to diversify to stay afloat.
Despite a team of researchers working to unravel the mysteries of Yellow Canopy Syndrome (YCS), the cause remains unknown and, in recent months, its spread south along the Queensland coast has been confirmed.
“There’s been a few sleepless nights, and just worry,” said Mr Shepherdson, who has grown cane across three farms, totally about 140-hectares, at Home Hill for 25 years.
“It’s an unknown, you’re fighting against something that you can’t pinpoint.”
As well as turning the leaves yellow, YCS affects the crops’ sugar content.
At its worst in 2013, Mr Shepherdson believes YCS accounted for at least a 30 per cent drop in yield over the farm.
“Yield, as in tonnes per hectare — we dropped from 144 expected for one particular block, down to 70,” he said.
“It’s been very difficult, financially it takes me below the cost of production, so I’ve had to borrow to stay afloat in those first couple of years.”
Farmer diversifies with mung bean, high amylase corn crops
Struggling to cope with lacklustre YCS affected cane, and without a concrete diagnosis for almost five years, Mr Shepherdson decided to channel his frustrations into diversifications.
“I’ve just grown a crop, two crops of mung beans on some fallow ground and we’ve now got some high amylase corn in that,” he said.
With 29 hectares of corn contracted to a buyer in Sydney, Mr Shepherdson’s gamble has provided a boost both to the farm’s bottom line — and perhaps more importantly — morale.
“It just responds. You water it, it gets green, it stays green. It’s been a really uplifting experience, I’ve really loved it,” he said.
“I would much prefer to grow that than cane at this point, and financially it seems it could be fairly rewarding, maybe not quite as much as cane, but the soil needs a break and that’s why we’ve done that as well.”
‘Sugar cane with a sugar problem’
Meanwhile, a team of scientists from Sugar Research Australia are working intensively to try and unlock the mysteries of YCS.
Field research is being conducted across 12 main trial sites, including on Mr Shepherdson’s property.
Analysis of leaf samples taken from Maryborough earlier this year, when signs of YCS were first spotted in the region, have shown a significantly higher level of sugar and starch in the YCS affected samples, compared to the sugar and starch seen in a healthy, green leaf.
“We believe that what’s happening is as starch and sugars build up in the leaf, everything really does get messed up in there,” said senior technician from SRA Gerard Scalia, who is involved in the YCS research activity.
“As photosynthesis is disrupted, the internal temperature of the leaf will heat up and finally you’ll get photo oxidisation, and that’s the yellowing that you see as a visual on the outside of the leaf.
“If it [the leaf] can’t export the sugar, the sugar just continues to build up and build up, so sugar cane with a sugar problem — it’s really quite bizarre.”
Canegrowers’ long history in successfully battling cane disease
Queensland canegrowers can take some heart that their industry has a long history in successfully battling disease.
Chlorotic streak disease (CSD) was first recognised in Australian cane crops in 1929, and it remains among the most widespread and common diseases affecting the industry.
CSD is characterised by white streaks along the cane leaf but despite the subtle symptoms, it can have a significant impact on yield.
It was first recognised in Australian cane crops in 1929, and remains among the most widespread and common diseases affecting the industry.
After keeping scientists across the globe guessing for almost 90 years, a team of Queensland researchers has finally identified the DNA of the unique water-borne organism that spreads CSD.
“It is quite a significant scientific breakthrough not only for sugar cane but for all plant diseases,” said SRA Biosecurity Manager Barry Croft.
CSD ‘a big problem’ when there’s lot of rain
At a quarantined research site at Woodford in south-east Queensland, researchers have been injecting hundreds of plants with the organism, to see which cane varieties offer the best resistance to the disease.
“We can get symptoms really quickly, in around five weeks, so we’re hoping that we can develop a rapid screening technique for our plants,” said SRA senior researcher Kathy Braithwaite.
Once the most disease-resistant cane is identified, that information can be given to growers to guide which crop to plant and which to avoid, particularly in wet years.
According to Lawrence Di Bella, a canegrower from Ingham and the head of Herbert Cane Productivity Services, the breakthrough is significant for growers in the tropics.
“We can get metres of rain — so our average annual rainfall in the Ingham area is 2,200mm, that’s quite large compared to some of the other places in Australia, so it’s (CSD) quite a big problem when we get a lot of rain,” he said.
“This is going to help us a lot because in the past we would plant a variety without any knowledge of its resistance, so we would be taking a gamble when a variety was released and sometimes it hadn’t paid off for us in the past.”