Archive for the ‘Biocontrol’ Category

Bacteria hitch a ride on raindrop spray (with implications for tackling kiwifruit Psa)

New research reveals how raindrops on soil create bioaerosols – tiny droplets of bacteria-laden water – which can help spread harmful microbes, including kiwifruit pathogen Psa.

Our attention was drawn to it by a Sciblog post (HERE).

Although soil bacteria are usually pretty slow at getting around, the post observes, wet weather has been suggested to give them a hand travelling large distances. But exactly how rain gets bacteria from the soil into the air has been something of a mystery – until now.

New research, published in Nature Communications, details the exact mechanism that allows bacteria to get airborne with the help of rain.

Using high-resolution imaging, Cullen Buie and colleagues from MIT’s Department of Mechanical Engineering tracked the fine mist released by a fizz of bubbles created when a drop of water hits soil. The researchers found that the tiny droplets in this mist carried up to several thousand bacteria from the soil and is some cases the bacteria remained alive for more than an hour afterward.

“Imagine you had a plant infected with a pathogen in a certain area, and that pathogen spread to the local soil,” Buie says. “We’ve now found that rain could further disperse it. Manmade droplets from sprinkler systems could also lead to this type of dispersal. So this [study] has implications for how you might contain a pathogen.”

The team calculated that precipitation around the world may be responsible for 1 to 25 percent of the total amount of bacteria emitted from land.

You can read more about the research on Scimex.org

The authors note that their research is important for studying the spread of all manner of bacteria that could harm humans, animals and plants.

The Sciblogs post notes that one of the sample bacteria they used in their research –Pseudomonas syringae – has direct relevance to New Zealand.

A variant of this bacteria, Pseudomonas syringae  pv actinidiae (Psa) is all too well known among NZ kiwifruit growers as the cause of kiwifruit vine disease.

A 2010 outbreak of the disease in the Bay of Plenty has been calculated to cost the NZ kiwifruit industry up to $885 million over 15 years.

Psa is known to spread more easily with the help of wet and wild weather and this new research offers a deeper understanding of exactly how Psa might be fizzed up into the air by raindrops and whisked away in bioaerosols. It will also offer further avenues for research on how to best predict and limit the spread of the costly disease.

Plant & Food Research has been working on using weather data to model the spread of the the disease in Bay of Plenty orchards.

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Call for new organisms to be reclassified

When is a new organism no longer new?

The answer: an organism can be reclassified when it has formed a self-sustaining population and is not part of any eradication programme in New Zealand.

This rule can apply to any animal, plant, or microbe that arrived in New Zealand after the Hazardous Substances and New Organisms (HSNO) Act came into force on 29 July 1998.

The Environmental Protection Authority (EPA) is now seeking proposals to deregulate organisms that fit these criteria, so they can be reclassified as no longer new to New Zealand.

“The aim is to reduce the regulatory burden on anyone working with these organisms, perhaps to propagate or study them,” explains Ray McMillian, Acting General Manager of the EPA’s Hazardous Substances and New Organisms team.

“It means they won’t need to apply for approval to do that under the HSNO Act, so it makes it easier for them to do their work.

“Anyone can put forward a proposal for a ‘new’ organism to be reclassified. Examples include the Australian citrus whitefly and the bridal creeper rust.”

Proposals must be submitted by 5pm on Wednesday September 28 to the EPA’s New Organisms team.

All proposals will be evaluated by the EPA before a final decision to take the nextstep is made by the Minister for the Environment.

For more information, call 04 474 5581 or email: neworganisms@epa.govt.nz

Read more about deregulated new organisms [EPA website]

 

 

Radio NZ reports on biocontrol and the fight to eradicate bad weeds

Radio NZ has been reporting on the problem of weeds, both in native vegetation and on farms and orchards, and on the the Department of Conservation’s War on Weeds.

One interviewee was Hugh Gourlay, from Landcare Research, who discussed (here) his work as part of a team that works to find biocontrol agents to kill or knock back the worst weeds.

The work involves visiting the country of origin of a plant and hunting for diseases that infect it. The team is  also looking for insects that attack and eat any part of the weed, including the seeds, flowers, leaves or stems.

Hugh told Radio NZ it is sometimes possible to “knock a plant invasion on the head” with prompt action to hunt down and kill all the plants. Chemical control, using herbicides, is usually the next step, but at best it will “keep the problem at bay.” This leaves biocontrol as the best answer for widespread weeds.

Once potential biocontrol agents are identified they are imported into New Zealand and kept in strict quarantine, so they can be tested to see if they attack any plants other than the weed. “If they don’t attack anything else then we can look to release them.”

Describing some great biocontrol successes in New Zealand, Hugh cites St Johns Wort control in the 1960s as a “guiding light” success story. Ragwort (Jacobaea vulgaris), some thistle species and mist flower (Ageratina riparia) have had successful biocontrol agents introduced.

More recently, the broom gall mite and several species of beetle that attack Tradescantia have been showing great promise.

Darwin’s barberry is among Hugh’s recent projects.

“Darwin’s barberry continues to advance across the countryside in Otago and Southland. It takes over entire hillsides, and becomes quite a monoculture.”

Beginning in the early 2000s, the biocontrol team identified a seed weevil and a flower weevil in the plant’s native range in South America. The focus has been on the seed weevils, which have been released over two years.

Radio NZ’s “Our Changing World” recently featured a story about the wasp mite that is being investigated as a potential wasp biocontrol agent. It has also looked at the buddleia leaf weevil.

Moth and beetle join forces in the fight against tutsan

The Environmental Protection Authority (EPA) has approved a moth and beetle to help stamp out tutsan, or Hypericum androsaemum). which is is considered a serious agricultural and environmental pest in the central North Island.

The yellow-flowering shrub was introduced into New Zealand as a garden plant in the 1800s but had grown out of control by 1924 and has been a growing threat to hill country farming since the 1950s.

It thrives in the central North Island, particularly around stream margins and regenerating scrub. In some areas, such as the Waikato, landowners work with their regional councils to control the weed.

Although it’s not toxic, livestock will not eat it and removing it is time consuming. Even minor infestations require intensive effort and herbicides are usually used to control or reduce larger infestations.

As a result, tutsan cannot be bought, sold, propagated, distributed or included in commercial displays.

The EPA has approved the use of two biocontrol agents, a moth and a leaf-feeding beetle, to help in the fight to combat the weed. The larvae of the moth (Lathronympha strigana) feed on the leaves and stems of the plant in spring and burrow into the fruit, consuming its seeds. The leaf beetle larvae (Chrysolina abchasica), in large enough numbers, are capable of stripping the plant of its leaves.

Ray McMillan, the EPA’s Acting General Manager of Hazardous Substances and New Organisms, says using biological control agents, or nature’s enemies, is a cost-effective way of targeting and reducing the impact of pest plants such as tutsan without resorting to chemicals.

The application to use these agents was made by the farmer-led Tutsan Action Group.

War on ragwort with flea beetle makes $44 million savings for dairy farmers

A tiny insect’s huge appetite is saving New Zealand dairy farmers $44 million a year, Landcare Research reports. A quantitative study has revealed the “surprising” amount the Ragwort flea beetle saves in control costs.

“Until now we have only been able to speculate on the financial benefits of the Ragwort flea beetle to farmers,” said Landcare Research scientist Simon Fowler.

“We had no hard data. We had amazing before and after photos of the flea beetle’s work. But people need quantitative data so we revisited our research and we have now finished a national cost-benefit analysis”.

Fowler used data from a 2005 study conducted on the West Coast where the flea beetle has failed to thrive due to its wet climate. The amount of money West Coast farmers spent killing the weed was extrapolated across New Zealand’s dairy sector.

Fowler’s methodology, which factors in inflation and national dairy herd size, has been peer reviewed and is expected to be accepted for publication in the New Zealand Journal of Agricultural Research shortly.

He said:

“The figure took us all by surprise. It will be the first published post-release weed biocontrol agent economic analysis for New Zealand and we think it shows in a very tangible way how smart science can assist the primary sector.”

Ragwort, which invades pastoral land and is toxic to cattle and horses, is thought to still cost New Zealand dairy farmers $20 million a  year in control costs.

The flea beetle has wiped out ragwort on 50 per cent of New Zealand farms. But the weed remains a “moderate” problem on about 25 per cent of farms and the remaining farms – many in wet regions located on the West Coast, Taranaki and Northland – are still fighting it.

A second insect, a plume moth that thrives in wet conditions, is being deployed to tackle remaining ragwort strongholds and looks set to reduce the threat of ragwort further.

Ragwort flea beetle was shortlisted in New Zealand as a potential control agent in the 1930s but dismissed. Fowler said that decision had no scientific basis.

His calculations on the cost of that decision show it came to a staggering $8 billion.

That’s how much farmers spent on controlling Ragwort up until 1983, when the DSIR imported and released the flea beetle, Fowler said.

The latest flea beetle research was funded by the Ministry of Business, Innovation and Employment as part of Landcare Research’s Beating Weeds Programme.

Farmers can pick up tips on how to help the flea beetle flourish on their properties here. 

“Farmers can get on a continual treadmill of spraying herbicides to control the weed but that doesn’t give the flea beetle a chance, and only provides temporary relief. It takes a bit of nerve but sometimes they need to take a deep big breath and do nothing. Be patient and let the ragwort flea beetle do the work for you.

“Biocontrol agents are not always as successful and many fail to have any material effect. However, the flea beetle is a success story and our quantitative analysis shows how important these tools can be when we assess control agents.

The $44 million saving is ongoing, said Fowler, who is confident the little golden beetle will not do anything other than munch through this particular weed.

 

Rigorous tests for potential wasp biocontrol

Tests will soon begin to ensure a mite, with the potential to be used as a biocontrol agent against wasps, isn’t a threat to bees.

The mite, discovered by Landcare Research scientist Dr Bob Brown on wasp nests in 2012, recently has been recognised as a new species and named Pneumolaelaps niutirani.

It was identified and named by fellow Landcare Research scientist Dr Zhi-Qiang Zhang and Ministry for Primary Industries scientist Dr Qing-Hai Fan.

Dr Brown has been researching the mites’ potential as a biocontrol agent against wasps, which cost the country’s primary industries around $130 million a year and cause biodiversity loses.

He has found wasp nests where the mites are present are 50 to 70 per cent smaller than uninfested nests. Immature mites have also been found in nests indicating wasps could be a host.

However, other species in the genus of the mites are often found in association with bees. As a result, the next step is to conduct safety trials to make sure the mite does not pose a risk to honeybees or bumblebees.

In order to do this, bee larvae would be fed stable isotopes and the mites later inspected to see if it was in their system, Dr Brown said.

“Stable isotopes are molecules that act like a chemical marker that we can track. If the stable isotopes are found in the mites this will conclusively tell us they are feeding on the bees because there is no other way for them to acquire these molecules,” he said.

“We found the mites in low numbers in quite a few honeybee hives so we need to check out what their association is. It’s not uncommon for organisms to have a different association with other species and feed on different things. It is possible the mites are there because they hitched a ride on wasps that were robbing honey from the hive.”

The tests would begin as soon as Dr Brown had excavated wasp nests over the coming months and had access to the mites. Once complete, attention would turn to checking the mites were not harmful to native bees.

Dr Brown will also investigate the associations between the mites and wasps. In particular, if and how the mites are responsible for decreased aggression levels in the wasps and how they are managing to enter the nests.

“Wasps don’t like anything in their nest but somehow these mites are tricking them into letting them be there.”

He wanted to thank the public for their support after an appeal for wasp queens to assist his research saw him sent 436 from around the country. An analysis of the wasps found 35 per cent had a least one mite.

The Vespula Biocontrol Action Group contracted Landcare Research to investigate the mite’s potential as a biocontrol agent against wasps.

The research is funded by the Ministry of Primary Industries’ Sustainable Farming Fund.

EPA calls for submissions on weevil to control field horsetail weed

The Environmental Protection Authority (EPA) has opened submissions on an application to introduce the horsetail weevil (Grypus equiseti) as a biological control agent for the weed field horsetail (Equisetum arvense).

The application to introduce this new organism, from the Rangitikei Horsetail Group, is made under the Hazardous Substances and New Organisms (HSNO) Act 1996.

“Biological control agents, like the horsetail weevil, are used as natural enemies to reduce the populations of pests such as insects and weeds. We’re notifying this application to ensure that the EPA can consider all views about potential risks and benefits of introducing this horsetail weevil into New Zealand,” said Applications and Assessment General Manager Sarah Gardner.

Field horsetail is an invasive species and an unwanted organism under the Biosecurity Act 1993. It threatens native plants in sensitive habitats such as wetlands and on the banks of waterways. The aim of this proposed biological control programme is to limit the adverse effects of field horsetail where it occurs, and to reduce the rate and strength of invasion.

The horsetail weevil lays its eggs into the stems of the weed. The larvae feed on the stem, moving down into the plant’s roots and killing the stem. Larger larvae consume and break up the roots, reducing the ability of the plant to produce new fronds in spring. Adult weevils also feed on the stems, often causing the portion of frond above to die.

 The application notes that control of field horsetail using sprays or physical removal is problematic. Small infestations can be eradicated by constant removal of fronds or by repeated herbicide application, but this requires long-term persistent effort and is often unsuccessful as well as uneconomic.

Although its distribution is limited, field horsetail is already too widely spread for all infestations to be found and effectively treated.

It can be found in Whanganui, Rangitikei, Taranaki, parts of Greater Wellington and the west coast of the South Island. Field horsetail has also been recorded on the east coast in Havelock North, Marlborough, Canterbury and Otago.

No native plants or valued exotic plants in New Zealand are closely related to field horsetail. The closest relatives are ferns, but these are only remotely related. The weevil is well established in Europe and has only been recorded on horsetails.

The public are invited to make submissions on the application to the EPA. The submissions period closes at 5pm on March 11.

A public hearing may be held before a decision is made. The EPA will provide at least 10 working days’ notice of the hearing date, time and place. We’ll provide this information to all submitters and the applicant.

View application details and information

Find more information on submissions and the hearing process