Australian mushroom growers are using the same PCR testing technology used to detect COVID-19 in humans to manage major crop diseases impacting the industry.
Key points:
- Early detection is the key to preventing the spread of crop diseases on mushroom farms
- PCR testing offers faster results than growing mould in laboratories
- More than 5,000 samples have been tested across Australia
University of Sydney associate professor Michael Kertesz said PCR — polymerase chain reaction — testing was faster than a previous method they were using.
“It’s a fast turnaround compared to growing up these moulds in the lab and then identifying them, which can take a week or two,” he said.
“Turnaround time for these PCR tests is 48 hours.
“[We use] what’s called multiplex PCR.”
Professor Kertesz said it enabled them to test for four key crop diseases, impacting yield, at the same time.
Early detection paramount
Time is of the essence when detecting disease incursions on farms, according to Australian Mushroom Growers Association general manager Leah Bramich.
The biggest farms around the country can produce 120 tonnes of mushrooms a week, so shutdowns due to crop disease can have major impacts on the supply chain.
“Growing rooms produce a huge volume of mushrooms, and they’re interconnected,” Ms Bramich said.
“If there’s a problem in one room, it can very quickly spread to the others.”
She said the preventative measures were there to isolate and treat a problem early, “so it doesn’t turn into a big farm outbreak and a massive risk to the industry”.
“An issue on-farm will cost hundreds of thousands of dollars, if not more, for it to be rectified,” Ms Bramich said.
How the tests are taken
Swabbing for mushroom diseases is a lot less invasive than the COVID-19 tests humans have become accustomed to.
Growers take their own samples and send them off to a laboratory for testing.
“We test on the floor of the growing room, we test on the crop, we can even test in the coffee room just in case the pickers have had some on their fingers,” Professor Kertesz said.
“The best place to test is actually the drain at the bottom of the growing room.
“[We] take samples with a Q-tip [cotton swab].
“Alternatively, if you want to open up the floor, [we use] a paint roller, which will sample a large area or small roller for coffee rooms.”
The PCR tests are being used successfully in the industry after years of trial work.
“Over 5,000 samples have been dealt with in the past two years,” Professor Kertesz said.
“There are about seven farms around the country that are doing it — mainly the large players.”
Testing is available to the whole industry but, due to costs associated, only big operations have been using it as part of risk management programs.
What about RAT tests?
Rapid Antigen Tests (RATs) were rolled out for home testing during the COVID-19 pandemic, but are not being used by the mushroom industry.
Professor Kertesz said the industry considered the option.
“The sensitivity of the antigen tests was so much lower than the PCR tests that we went with PCR,” he said.
He said some farming operations were discussing whether to set up their own lab facilities to process results but, for now, it was run via a central lab.
Self-test kits could become a reality in the future, but not for disease detection.
Professor Kertesz was currently working on developing a test, similar to a RAT, to determine microbes in compost in order to predict mushroom yield.
“I think this will be really flexible and a great benefit for the farms,” he said.
“We’ve just got to get the sensitivity up to a level.”
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