Mango twig tip dieback spreading in the NT as more trees get bulldozed
It's estimated up to 40,000 mango trees have been bulldozed in the last two years because of mango twig tip dieback. (Supplied: Callum Hutcheson )
In short:
A fungal disease called mango twig tip dieback is spreading across orchards in the Darwin region of the NT.
The chief executive of Australian Mangoes says the disease has become a "serious issue" for the industry.
What's next?
A multi-year research program is starting to provide some answers to growers, but more research is needed.
It is estimated that between 30,000 and 40,000 mango trees have been bulldozed in the Northern Territory as growers struggle with a fungal disease called mango twig tip dieback (MTTD).
The disease has affected farms across the Greater Darwin region, with the famous Kensington Pride (KP) variety appearing to be one of the more susceptible cultivars.
It has been estimated that up to 90 per cent of KP orchards in the Darwin region have some level of infection.
Australian Mangoes chief executive Trevor Dunmall said it had become a serious issue for the industry.
"To see mango trees looking so sick, it would make you cry," he told ABC Rural.
"We drove past some orchards, where trees are bulldozed up and ready to burn ... so you can't get more serious than that."
At present, MTTD outbreaks have been confined to the Greater Darwin region, but Mr Dunmall said the entire industry was watching closely.
"Our researchers indicate the pathogens that are linked to MTTD are endemic across many regions," he said.
"But why the symptoms are expressing in such a serious extent in Darwin is what the research is focusing on, and then the aim is to find management solutions."
In its 2025 budget, the NT government committed $1 million over two years to fund an integrated research program to combat MTTD.
Some early results from that research were presented at a field day in Berry Springs in front of a large crowd of growers.
Mango growers gather to hear the latest research on mango twig tip dieback (MTTD). (ABC Rural: Matt Brann)
What is killing mango trees?
For a long time, the cause of the mango twig tip dieback was a mystery.
But researchers now know it is a plant disease linked to Botryosphaeriaceae fungi and plant stress.
"The disease affects young shoots, twigs and branches, resulting in canopy thinning, reduced flowering and yield," said the NT Department of Agriculture's progress report.
"Early detection and pruning out of infected twigs can reduce spread and minimise yield loss."
It said the dieback was increasing across Darwin orchards in both young and mature trees and "affecting multiple cultivars (varieties)".
Research into MTTD has included injecting trunks with encapsulated fungicides. (ABC Rural: Matt Brann)
The department said the disease was difficult to manage once established in an orchard and the bad news for growers was it seemed no single control method would be effective.
"MTTD is a complex stress-driven disease which will require integrated management and continued research," growers were told.
In its presentation, the department asked growers to consider the following:
- Reassess high-stress floral induction practices
- Avoid pruning during humid and wet conditions if feasible
- Protect vulnerable flushes, particularly during the wet season
Mango twig tip dieback can stop a tree bearing fruit and eventually kill it. (ABC Rural: Daniel Fitzgerald)
Tracking spores using AI
It is understood MTTD is spread via spores produced on leaves, dead twigs and branches of infected trees, which are then dispersed by wind and rain splash.
Various experiments are taking place in the NT to try to better understand the disease and how to control it.
One trial involves the real-time monitoring of airborne spores using a unit from Australian agtech company, BioScout.
"So we are doing lab-grade analysis on pathogens and spores, but outside in this mango orchard in real time," BioScout's Charles Simons said.
"It's automated microscopy that can tell a farmer what diseases and pathogens are floating around your farm, and what are the risks to your crop."
BioScout has installed one of its automated disease detection units in a mango orchard impacted by MTTD. (ABC Rural: Matt Brann)
He said the artificial intelligence within the technology had now been trained to detect spores associated with MTTD.
"We can now detect the spread of that spore across a farm and alert farmers to say, 'Don't prune today or maybe you need to spray something,'" he said.
"I know there's no fungicide for this (MTTD) at the moment, but things can change quickly."
Mr Simons said the money spent by farmers on fungicides was increasing globally, with growers often spraying to stop a disease that might not be in the crop.
He hoped his company's technology could help and felt confident mango growers would get on top of the MTTD issue.
"I think this battle can be won," he said.
"It's going to take some time, but there's some exceptional young farmers in the NT, and we've just got to better understand it (MTTD)."