Green peas are a lucrative industry for Tasmania but severe outbreaks of collar rot have created a significant challenge for growers and threaten the commercial viability of the crop in wet growing regions.
Tasmanian Institute of Agriculture (TIA) PhD candidate Peter Targett is investigating the factors that contribute to collar rot and his work will help researchers develop strategies to prevent and manage the disease.
"It's one of those problems that's not quite obvious to industry and it really needs someone with a fine-tooth comb that goes through and just eliminates factor by factor to find the answers," Peter said.
It's an important topic of research as Tasmania produces about 95 per cent of all green peas grown for processing in Australia.
"2022 was a particularly poor year for peas in Tasmania. It was a higher-than-normal rainfall year and that's thought to result in a higher level of disease that leads to poorer yield outcomes," Peter said.
"Pea yields in 2022 were reduced by about 22 per cent compared with the three-year average. That means a $3.4 million loss at the farm gate that year and the far north-west of Tasmania was particularly hard hit.
"Collar rot can really reduce the yield of green peas. One of the causes is Ascochyta fungi which survives for years in the soil. When a pea crop is planted it infects the plant stem and travels up producing millions of airborne spores which can then take out the whole crop."
As part of his research, Peter has conducted crop surveys around the state where he has randomly sampled 20 paddocks and monitored for disease. He's noticed some interesting results in the north-west.
"All of these crops have a similar soil type, they all experienced very similar weather conditions and they were all planted with the same variety of seed and planted at a similar time. However, the yields within these closely related paddocks are very variable and that suggests that it's not just the weather that's at play here," he said.
He monitored for disease at early and late stages of pea growth and noticed that yields reduced as the collar rot disease increased.
"There was actually a really high correlation between foliage disease at early and late sample times and yield. This is significant because if you are a grower and you can predict yield then you can actually make management decisions to stop that disease cycle from snowballing," he said.
His research has so far delivered other significant findings.
"For the last 30 plus years our primary focus has been around Ascochyta foliar which affects the collar of the peas and it produces above ground spores, but what I found in the early growth stage was that Fusarium was just as much of an issue," he said.
He hopes the findings will enable Fusarium to be upgraded to a high priority disease.
"Only Ascochyta is listed as a high priority disease but from my research there's strong evidence to move Fusarium up from moderate to high and by doing so that will actually unlock a lot of government support systems for us," he said.
"It creates a better case when we ask for research funding and it will create best practise management guides for growers.
"Not every grower is impacted by the disease so my project is investigating why some growers are having much better results compared to growers that are getting hit really hard."
This PhD project is being delivered through Hort Innovation's Hort Frontiers strategic partnership initiative.
Want to know more? Listen to Peter Targett present at the 2024 TIA Vegetable Research Facility Field Day: https://www.youtube.com/watch?v=JA4vc9tnIeg&t=234s
