Posts Tagged ‘native plants’

Indigenous fungus may help to control wilding pines

Wednesday, June 16th, 2021

An indigenous New Zealand fungus may help to control wilding pines – one of the country’s most ecologically damaging weed species – a student’s research project shows.

​Wilding pine control costs New Zealand millions of dollars a year, and involves the costly and time-consuming methods of cutting down the trees and spraying herbicide from the air. Control seldom totally eradicates the pines, which often reinvade sites some years later.

Armillaria novae-zealandiae, also known by Māori as harore, is a fungus that feeds on decaying wood. It is common in native forests, where it is a natural part of the ecosystem, helping to decay fallen trees. But if it gets into pine plantations it is seriously destructive, killing seedlings and reducing growth.

In a Bio-Protection Research Centre student research programme, biology student Genevieve Early, investigated how well A. novae-zealandiae and two closely related species established on wilding pine species.

Supervised by BPRC principal investigator and University of Canterbury Professor Ian Dickie and his colleague Dr John Pirker, she tested what age of wood it grew best on (ranging from live and freshly harvested wood to old and decayed wood).

“The research aimed to address knowledge gaps in our understanding of Amillaria, and eventually investigate whether we could use it as a biological control of invasive pines,” says Genevieve.

“Some of the questions we have about using it, for example, are whether we can introduce it to grassland areas that are susceptible to wilding pine invasions, where it doesn’t currently exist, and whether introducing it at the same time as pines are felled would prevent reinvasion.”

Her results were promising. “Armillaria novae-zelandiae showed the best growth,” she says. “We tested several isolates of this species and all of them grew larger than the other Armillaria species. It also consistently grew most vigorously on live or freshly-felled pine wood.”

Armillaria’s strong growth on live or fresh pine wood is important,” Genevieve says. “It’s really promising that all the fungi grew best on live or fresh wood, as this implies that we could potentially design a way to inoculate wilding pine sites with Armillaria at the same time we are manually clearing trees and using herbicide. That could be practical and economical if we don’t have to plan more site visits to use the fungi.

“We also want to find out if this will accelerate decomposition and reduce wildfire risks.”

Genevieve said A. novae-zelandiae has been used as a food source by Māori, who should be involved in continuing research. “Using it as a biological control may be of particular interest to iwi in areas badly affected by wilding pines, as a way of protecting landscapes and ecosystem values.”

Prof Dickie said his group was seeking funding to continue the research, particularly looking at how Armillaria affected native seedlings, to test whether it could be used to clear pines in areas where ecological restoration was planned.

“Until now, we’ve been good at killing pines, but not at restoring ecosystems,” says Ian. “We are winning the battles, but losing the war. This fungus may be the key to not just killing pine, but to keeping it from reinvading, and to restoring ecosystems.”

You can view a video of Genevieve Early presenting her research here.

Native plants may be weapon against soil contamination

Wednesday, June 16th, 2021

New Zealand’s native plants may help to reduce bacterial contamination caused by dairy effluent, a new study suggests.

​Researchers from the Bio-Protection Research Centre, ESR, and the University of Canterbury have shown northern rātā (Metrosideros robusta) and swamp mānuka (Leptospermum scoparium) can reduce the amount of Escherichia coli (E. coli) in soil by 90%, compared with ryegrass (Lolium perenne), and in less than one-third of the time. They worked in partnership with Ngaa Muka Development Trust and Matahuru Marae in Waikato.

The research, published in Applied Soil Ecology, aimed to investigate the antimicrobial properties of New Zealand native plant extracts and test if they were effective in soil.

First they tested leaf extracts of 12 plants, chosen because they were either medicinal plants, poisonous, or had a strong scent. These included harakeke (Phormium tenax), golden ake ake (Olearia paniculata), mānuka (Leptospermum scoparium), kawakawa (Piper excelsum), koromiko (Veronica stricta), ngaio (Myporum laetum), golden Spaniard (Aciphylla aurea), Spaniard (Aciphylla sublabellata), and horopito (Pseudowintera colorata), as well as swamp mānuka and northern rātā.

Swamp mānuka, northern rātā, and horopito showed antimicrobial properties, and so they were tested to see if they reduced bacterial contamination in soil.

The scientists grew seedlings in pots, and, once the seedlings were large enough, added equal amounts of dairy shed effluent to each pot. They watered the pots to simulate rainfall, and then tested for E. coli on days 1, 3, 7, 14, and 21.

Results indicated the amount of E. coli in the soil would reduce by 90% by day 14 in the pots containing swamp mānuka and northern rātā. “Extrapolation from L. perenne data indicated that this reduction would happen by day 45.”

The roots of swamp mānuka and northern rātā both increase soil acidity, which researchers suggest may have caused the faster E. coli die-off.

E. coli tends to do better in soil that is alkaline to neutral pH,” said Dr Hossein Alizadeh, of the Bio-Protection Research Centre. “The roots of swamp mānuka and northern rātā change soil to make it more acidic, so that may be why E.coli dies off more quickly.”

However, the researchers did sound a note of caution. When soil was already saturated, irrigating it with dairy shed effluent resulted in E. coli leaching out of the soil very quickly before any plants could dilute or destroy it. This suggested that “high irrigation regimes” could result in more environmental contamination.

The authors say their results show the need for further field research.

“Future research in field conditions would show the potential and/or limitations of bioactive plantings for preventing faecal or microbial contamination of freshwater resources from contaminated soil.”

Full paper: Phytoremediation of microbial contamination in soil by New Zealand native plants,

Image: Gerald.w, CC BY-SA 3.0​ via Wikimedia Commons​​