Pine and pasture may harbour kauri dieback

The Government should be cautious about planting pine near northern kauri forests because research suggests they may act as reservoirs for kauri dieback, says an expert in the disease.

Dr Amanda Black, of the Bio-Protection Research Centre, says pine plantations and agricultural pasture may have a role in incubating and spreading the disease – as revealed by research for a Master’s thesis, completed by her student, Kai Lewis.

But at the same time, the Government is promoting an increase in commercial forestry – including radiata pine – as part of its 1 billion trees programme.

“We urgently need further research to clarify the role pine forests, pasture, and other plants play in incubating and spreading Phytophthora agathidicida – the organism that causes kauri dieback,” says Dr Black, who supervised the study and thesis by Mr Lewis.

“Until we are sure of what role they play, we should be very careful about planting any further pine plantations anywhere near kauri forest.”

For his thesis at Lincoln University Mr Lewis studied how well P. agathidicidareproduced in three types of soil: kauri forest, pasture, and pine forest. He collected samples near Waipoua Forest in Northland and one of the original mainland sites from which kauri dieback has spread.

Results showed that in its early stages of development P. agathidicida reproduces much more rapidly in pine forest and pasture soil than it does in kauri forest soil. In pine forest soil it also produces more long-lived spores (oospores).

Other research reported earlier this year showed P. agathidicida infected other native plants, including tanekaha, suggesting more potential hosts need to be examined.

Mr Lewis’s research also showed that P. agathidicida could infect Pinus radiata and several common pasture plants, even those that show no symptoms. This suggested other plants and soil may act as a reservoir for P. agathidicida.

“This raises the possibility that kauri dieback may be moving from pine plantations and pasture into kauri forests, carried by people, animals, and even on machinery,” says Dr Black.

“We urgently need further research to find out if this is happening and how. Until we know the answer, we need to be very careful.”

In his thesis Mr Lewis said investigating the role of unfenced pasture next to kauri forests was a high priority for further research.

He also found two other species of Phytophthora (P. pini and P. gregata), which can infect several plant species, were present in kauri forest and pasture soils. Their possible role in infecting native trees is another high priority for further research.

A paper submitted to an academic journal as a result of this research is under review. Another is about to be submitted.

One of the papers outlines the discovery of the two new species of Phytophthora in New Zealand, the other looks at the effects of fragmented landscapes on the growth and survival of P. agathidicida.

The full thesis from Lincoln University’s Research Archive can be downloaded HERE.

Source: Bio-Protection Research Centre

 

 

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Drought will bring more crop disease, scientists warn

New Zealand’s land-based primary industries need to get ready for increasingly serious crop disease as climate change causes more and longer droughts, according to new research.

In the journal Australasian Plant Pathology, the authors of the study say climate change is expected to bring more droughts in many parts of New Zealand, and more droughts are “likely to increase the severity of a wide range of diseases affecting the plant-based productive sectors”.

Scientists from the Bio-Protection Research Centre, Scion, Lincoln University, AUT University, Landcare Research and the University of Auckland analysed the potential impact of climate-change-induced drought on several commercial plants and their diseases.

They found that in most instances “increased drought is expected to increase disease expression”.

The probable negative effects of drought include

“…a predisposition of hosts to infection through general weakening and/or suppressed disease resistance”. More frequent and more severe droughts could also lead to “emergence of enhanced or new diseases of plants that can reduce primary production”.

New plant disease pressures are expected to occur

“… with potentially devastating impacts for New Zealand’s productive sectors.”

But the news is not all bad.

“Drought may reduce the severity of some diseases, such as Sclerotina rot of kiwifruit and red needle cast (RNC) of radiata pine,” the scientists said.

And in some cases it could “activate systemic defence mechanisms resulting in increased resistance to infection”.

In an extended case study the authors said that the effects of increased drought on New Zealand’s Pinus radiata industry would depend on many factors, including whether drought happened early or late in the season.

“There is urgent need to study the impacts of the different levels of drought and different levels of RNC severity to understand the thresholds at which radiata pine plantations would still accomplish their economic and ecological roles.”

Lead author Dr Steve Wakelin, of the Bio-Protection Research Centre and Scion, said it was essential that more research was carried out so each industry could prepare for the effects of drought.

“Many industries, such as agriculture and horticulture, may have time to gradually change over the next 20 or 30 years, to avoid the worst effects of drought or even take advantage of any opportunities the changing climate may bring.

“However, plantation forestry does not have the luxury of flexibility. What is planted now will need to not just survive but thrive in whatever climate and disease conditions are prevailing in the next 20, 30, or 40 years.

“It’s essential that primary industries with a long production cycle start assessing and addressing the risks and opportunities a much drier climate will bring.”

***

Wakelin, S.A., Gomez-Gallego, M., Jones, E. et al. Climate change induced drought impacts on plant diseases in New Zealand Australasian Plant Pathol. (2018) 47: 101.

Source: Bioprotection Research Centre

Alien pest incursions threaten New Zealand’s primary industries

New Zealand’s environment and primary industries are under threat from pests we don’t even know about yet, says Professor Philip Hulme of the Bio-Protection Research Centre, based at Lincoln University.

Professor Hulme was part of a large international collaboration of scientists who analysed 46,000 recorded sightings of invasive animal and plant species around the world. Their research* showed that one in every four new pest incursions were from species that had never before been recorded as being invasive.

“We looked at patterns over the last five centuries to see whether there was any evidence of a slowdown in the number of new pests and weeds emerging around the world, but there wasn’t,” said Professor Hulme.

“Just as many new pests are emerging now as in previous centuries.

“If we look at the pests and weeds already in New Zealand, most have come from Europe, Australia or North America, our traditional trade partners and sources of immigration. However, Asia is now becoming more important to both trade and immigration, and this is where many new pests and weeds appear to be coming from.”

Professor Hulme says we may be entering a new era for biosecurity as we face an increasing wave of unknown emerging pest species.

“We need to make sure our biosecurity system is sufficiently flexible and well-resourced to deal with unexpected incursions by species we probably will know nothing about,” says Professor Hulme.

“The responsibility rests with all of us: government, industry, the public, and every tourist who crosses our borders,” says Prof Hulme.

He urged everybody to be vigilant, understand the risks and take action in a way that minimises the chances of any new pest or disease crossing our borders.

*Seebens, H., Blackburn TM, Dyer EE, Genovesi P, Hulme PE et al. (2018): Global rise in emerging alien species results from increased accessibility of new source pools. Proceedings of the National Academy of Sciences. doi: 10.1073/pnas.1719429115

Kauri dieback fungus may have been in NZ for longer than previously believed

Phytophthora agathidicida (PTA), the fungus-like organism that causes kauri dieback, has been in New Zealand much longer than previously thought, a study led by Bio-Protection Research Centre researchers based at Massey University suggests.

Plant geneticist Dr Richard Winkworth and collaborators have been using genome sequencing to investigate when PTA arrived and how it has changed since arriving.

“It had been suggested that PTA arrived in New Zealand not long before the first diseased trees were found in the early 1970s,” Dr Winkworth says.

“However, our results suggest PTA was diversifying in New Zealand kauri forests around 300 years before that. It must have arrived even earlier. Humans may have brought it here – perhaps the pathogen was carried to New Zealand by Polynesian settlers or the earliest European explorers – or it may even have been here before humans arrived.”

The researchers have sequenced and analysed complete mitochondrial genomes of 17 PTA samples collected from sites across the geographical range of the disease.

“The samples we have collected suggest several genetic subgroups within PTA,” Dr Winkworth says.

“To better understand the history of spread through the kauri forests we need to increase our sample size. However, we do see, for example, that several genetic subgroups are present in the Waitākere Ranges, perhaps as the result of human activity.”

These results raise an important question: If PTA has been in New Zealand for at least the last 300 years, why has it only recently become a significant problem?

“The results suggest that the relationship between PTA and its host may have changed,” Dr Winkworth says.

There are several ways this might have happened. One is that genetic changes to PTA have made it more virulent. “It is a possibility, but our results suggest it is not as simple as a single pathogenic form evolving and spreading through the forest,” Dr Winkworth says.

An alternative is that environmental changes have resulted in the disease emerging. The research results are consistent with this possibility.

“Since humans arrived, we have been altering New Zealand environments. Perhaps the combination of heavily fragmenting the kauri forests together with ongoing human-mediated disturbance and climate change has led to emergence of the disease. Perhaps we introduced another pathogen that, in combination with PTA, results in disease.

“If we are to fight back effectively we need to better understand the relationship between when PTA arrived, its pattern of spread, and the emergence of kauri dieback disease,” Dr Winkworth says. “Identifying why kauri dieback disease emerged might help us to move beyond containment to managing and controlling it.”

The research team has also been developing a cheap, robust DNA test that is simple enough for community groups to use in the field, but that is as accurate as laboratory-based testing.

“We are hoping to evaluate the test in field trials in the next few months.” Dr Winkworth says. “We hope that this will make it easier to monitor where PTA is, both for the purposes of management but also to enable further research.”

This Massey University-led research has been largely funded by the Bio-Protection Research Centre, and has involved researcher contributions from Manaaki Whenua Landcare Research, Toi Ohomai Institute of Technology, Scion, and the University of Auckland.

Funding confirmed for bioprotection research

The Bio-Protection Research Centre – a Centre of Research Excellence located at Lincoln University – has had its funding confirmed for another five years.

Established in 2003, the centre’s primary goal is to strengthen the value of New Zealand’s pastoral, horticultural and forestry industries through research to generate next generation bioprotection (biosecurity and biocontrol) solutions.

“We are absolutely thrilled that the Tertiary Education Commission has continued to fund the Bio-Protection Research Centre until 2020. The work this Centre does is fundamental research that underpins plant bioprotection and plant biosecurity for New Zealand and is strategically relevant,” says Lincoln University Deputy Vice-Chancellor – Scholarship and Research, Dr Stefanie Rixecker.

The BPRC brings together New Zealand’s leading experts in bioprotection, and is a partnership between Lincoln University, AgResearch, Massey University, Plant & Food Research and Scion.

It includes collaborations with several other national and international research institutes and incorporates one of the strongest bioprotection postgraduate training groups in the Southern Hemisphere.

Former students are employed in research, industry and policy positions throughout the world.

The centre has three main research themes focussed on protecting the plant-based systems in New Zealand: pests and pathogens, biological controls, and biosecurity and invasion.

“The BPRC research is led by outstanding scientists who are leaders in their respective fields and the quality of their scientific work is highly respected,” says Bio-Protection Research Centre Director, Professor Travis Glare.

The funding gave financial security to the centre for the coming five years to continue to work very closely with other government organisations and industry, to develop novel bioprotection tools and solutions, Professor Glare said.

Lincoln student in frontline of battle against stink bug

Lincoln University PhD student Laura Nixon is working on the development of a weapon in the fight to stop the brown marmorated stink bug coming into the country.

The bug is regarded by New Zealand’s horticulture industry as one of the top six pests of concern.

Ms Nixon’s research is funded through a multiorganisational research collaboration, Better Border Security (B3) and she is based at the Bio-Protection Research Centre on Lincoln’s Te Waihora campus.

Her aim is to come up with a way to chemically detect an infestation of the bugs in a confined space such as a shipping container, one of the ways it is envisaged the insect could make its way into the country.

The brown marmorated stink bug is an agricultural pest found in Asia, but it has invaded the United States and it is considered highly likely it could successfully establish in New Zealand if it gets here.

Since the insect arrived in the United States in the mid-1990s it has occasionally multiplied into plague proportions. In 2010 it caused US$37 million damage to apple crops across several states.

It feeds on more than 300 hosts, primarily fruit trees and woody ornamentals but also field crops. Almost any crop can be at risk.

Ms Nixon says the chemical compound, or the stink, the bugs emit when disturbed has been identified but she will work on trying to distinguish it from amongst other naturally emitted odours.

Initially she will work with native stink bugs, which are not considered pests, and then travel to the United States to see if her results can be used on the pest species.

She says the bugs are closely related so it is expected they will.

Ms Nixon says the bugs tend to live in big groups or aggregations, so if one container gets through then there could be a problem.

Hopefully her work will ensure it is stopped at the border, she says.

She says the method could be used to detect other insects such as ants and harlequin ladybirds which are also considered pests, though they present other challenges as they give of lower odour levels.

Her role involves developing the chemistry to the stage the odour can be detected and the commercial application may be undertaken by others.

The smell of success: insect pests avoid boosted pasture grasses

A  study from the Bio-Protection Research Centre has shown for the first time that pasture grasses containing beneficial microorganisms are less attractive to soil-dwelling insect pests.

Most New Zealand ryegrass and fescue pastures contain beneficial microorganisms that live within the grass shoots. These fungal endophytes are key to the country’s healthy grasslands. In return for food and shelter the endophyte can help its host grass resist insect attack, survive droughts, and even protect against overgrazing.

Insect pests are attracted to plants by odour as they can smell minute amounts of chemical compounds that tell them if a plant is damaged or healthy.

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