Collections / Biocontrol of weeds

Weeds in New Zealand are a growing problem, costing this country billions of dollars in lost production and in control efforts. Weeds often causing irreversible damage to ecosystems. For widespread and entrenched weeds, biocontrol is potentially a cost-effective, low-impact, long-term solution.

Biological control uses one living organism to control another. In 'classical biocontrol', host-specific agents (usually insects) are released into the wild to establish and breed up. Once they are well established, there is no need to make further relaases as the agents will persist forever.

However, before new control agents are introduced, researchers survey the weed in New Zealand to see if there is already something here causing significant damage to the weed.  Usually they don't find anything useful but if they do, then new agents are chosen to complement these.  To find new control agents, researchers study the weeds in their native country to find the most damaging natural enemies. Considerable safety-testing is then undertaken to ensure the potential agents are host specific, i.e. they attack the target weed but not other plants.

Once overseas safety-testing has been completed and a permit has been issued to bring the potential agents into New Zealand, a small consignment is imported into a specialist secure containment facility at Lincoln.

The agents are kept in containment until they have been positively identified and verified parasite- and disease-free. Some further host-specificity testing may also take place.

Finally, before they can be released into the wild, a case is made to the Environmental Risk Management Authority (ERMA) for their release. ERMA consults with all sorts of interested groups before making its decision.

Lots more information about biocontrol of weeds can be found on the Landcare Research website.


New Invertebrate Containment Facility boosts biocontrol

Lynley Hayes of Landcare Research says “Weed biocontrol in New Zealand relies on importing potential agents from overseas via a secure containment facility in which to safely confirm the identification of the species, conduct host-specificity testing, and check that the agent is disease and parasite-free.”

The facility that the biocontrol of weeds team had been using at Lincoln was 30 years old and increasingly inefficient and unreliable, with electrical and plumbing systems often breaking down. Once, when one of the air conditioning units failed over a weekend, the rearing rooms heated up to over 40°C cooking all the poor precious insects.  Definitely time for an upgrade!

The new facility is known as the David Miller Invertebrate Containment Facility. Dr Miller was a prominent figure in New Zealand entomology and an early driving force for biocontrol of weeds research. (More about him at the end.)

 PC2 for invertebrates

Hugh Gourlay working in the containment facilityPhysical containment facilities for invertebrates must be to the PC2 standard (magnetically-sealed doors, no opening windows, all gaps or cavities must be sealed, and there must be fine mesh on all exit points - such as for plumbing or air conditioning - so that when all the doors are closed the inside of the building is a ‘seamless sealed cavity’.

The new facility actually exceeds PC2 requirements because of four extra features: an airlock (the outer door must be closed before the inner one into the PC2 area can be opened); all waste water is steam-treated; all air in the ventilation system goes through a sealed HEPA filter (filtration system for micro-organisms); and a negative pressure airflow is created by blowing air into the corridors and internal spaces and sucking it out of the containment rooms (the slight draft going into rooms means nothing will be accidentally blown out of them). 

There are 13 rooms, one office and three labs (two in containment and one not).  Five of the rooms are dedicated PC2, four are for rearing insects not requiring containment, and the remaining four have the flexibility to be either depending on which doors are locked.  Another novel feature is that two rooms have glass ceilings for natural light because, over the years, the team has found that for some insects do not thrive or breed under artificial light. 

 The first residents

The first insect residents moved into their new home in June 2010: four Tradescantia (Wandering Willy)  beetle species, a woolly nightshade lacebug, and two potential moth plant agents. From now on, any new species imported from overseas will take up residence as they arrive. 

The facility will be used by staff across all of Landcare Research and will eventually house dung beetles plus other insects associated with weeds that are not present in the South Island. Lynley says that while they expect the facility to be running at full capacity a lot of the time.

 Resource efficient

With resource efficiency in mind, the builders kept landfill waste to a minimum by sorting waste and recycling it where possible. Records were also kept of the amount of water, power, vehicle kilometres and materials used so that carbon emissions associated with the construction could be calculated. 

The building is covered in ‘kingspan’ sheets, consisting of two layers of aluminium with a polystyrene-type core for added insulation so less energy is used to keep the rooms at a constant temperature.  Rainwater is collected from the roof and held in retaining tanks for use within the facility. 

 Dr. David Miller, C.B.E. (1890-1973)

Widely regarded as one of the founders of professional entomology in New Zealand, David Miller was internationally respected for his work on biocontrol. He initially worked on forest and timber insects which led to the establishment of the Forest Biological Research Station at Nelson in 1929. The success of the New Zealand timber industry is largely due to research Dr Miller initiated on methods of timber preservation, particularly the control of insect pests. During the economic depression of the early 1930s he campaigned vigorously for backing from primary producer organisations, local bodies and banks to maintain the services of his highly skilled entomological staff. Under Miller’s guidance New Zealand had become a world leader in the field of biocontrol by the late 1930s, and helped to establish the Commonwealth Institute of Biological Control as well as the Commonwealth Institute of Entomology in London. Dr Miller became the director of the Cawthron Institute in 1956. He retired in 1959, but continued to work and publish.  Dr Miller was the author of many technical papers and books, including a Catalogue of the Diptera of the New Zealand Sub-region (1950), Insect people of the Maori (1952), Native Insects (1955), Bibliography of New Zealand Entomology (1956), and Common Insects in New Zealand (1971). He was made a fellow of the Royal Society of New Zealand and the Royal Entomological Society of London, he received the Hutton Memorial Medal, and in 1958 was made a CBE.


A million recruits could help the army

In 2009, Simon Fowler and Paul Peterson reported buckets of biocontrol beetles attacking heather, an invasive weed on the Central Plateau of the North Island. 

Heather (in flower) invading tussock on the Desert PlateauHeather might be nice in the Scottish highlands but on the Central Plateau of the North Island (where silly misguided settlers planted it deliberately), it is a pest plant that’s seriously hard to control. Quite apart from driving over it in tanks and light armoured vehicles, the Army have been using herbicide to manage heather. However herbicides are expensive, produce only short-term results and no-one likes all those chemicals getting in to the environment anyway. In theory, biocontrol is the ideal solution but it is proving a hard battle.

Despite struggling for 13 years to get one of the world’s most promising biocontrol agents working in New Zealand, a watershed point may have finally been reached in 2009.  At one site on New Zealand Army land, where 500 heather beetles (Lochmaea suturalis) were released 8 years ago, Simon Fowler and Paul Peterson now estimate that a million beetles (or two 10L bucket loads) have made themselves at home on 11ha of heather (Calluna vulgaris) infested tussock grassland. The beetles are systematically munching their way through the heather leaving, as expected, all other plants untouched.

Adult heather beetleSince 1996, Simon, Paul and a number of others, have been releasing heather beetles  to help the Department of Conservation and New Zealand Army deal with a >50,000 ha infestation of heather on the Central Plateau of the North Island. As the heather beetle is a host specific pest of heather in its native range (where heather is a valued native plant), it was seen as a perfect solution to help deal with our heather problem in New Zealand.

Yet since the beetle’s importation from the United Kingdom in 1996, results have been largely disappointing. After much research Simon and Paul now believe that large fluctuations in spring temperatures at high altitude, low soil nitrogen levels and small beetle size (due to genetic bottle necking) are all probable causes of previous poor establishment and performance. “We still don’t understand the most critical aspects of successful beetle population establishment and growth but relatively mild spring conditions over recent years, releasing beetles at lower altitude sites, and adding nitrogen to release sites have probably contributed to recent successes,” said Paul. Research is ongoing to test the theory that fertilizing with nitrogen at release points can help ‘kick start’ populations through better nutrition allowing beetles to become larger and have more reserves to cope with climatic challenges.

If outbreaks in heather beetle populations continue to grow exponentially, we would expect beetles to disperse over 513 ha next year and 10,000ha the year after that . At this rate beetles could move through the entire heather infestation on the Central Plateau within 3 years. However, a more conservative and realistic model predicts beetles will infest 36 ha next year and 75 ha the year after that (assuming a maximum dispersal distance of 150m each year). But other scenarios are possible too. “Beetles may start to fly on mass as the density increases resulting in smaller outbreaks budding off the main one”, explains Simon.

Paul says that "the best bit of working on the Central Plateau is the relative peace and the awesome feeling of space. It's hard to imagine that some people actually have agoraphobia. "

"The worse bit (which can also be the best bit mind you) is the climate. Temperatures can fluctuate through more than 40°C in just 24hrs. It's probably one of the few places in the country where you could potentially have your sweat freeze. There's a nice mental image for you!"

Contributors to the project include:

Harry Keys and Nick Singers (DOC); John Mangos (New Zealand Army); Richard Mallinson (Environment Bay of Plenty); Peter Wigley (Biodiscovery); Paul Barrett and Jens Jorgensen (Massey University); James Shepherd, Shane Hona, Greg Arnold, Guy Forrester, Quentin Paynter, Shaun Forgie, Merilyn Merrett,  Lindsay Smith and Helen Harman (currently or formerly of Landcare Research); Brent Sinclair and Caroline Williams (University of Western Ontario, Canada); Dmitry Musolin (Kyoto University, Japan); and David Renault (Université de Rennes, France). This work was funded by the Department of Conservation, the New Zealand Army and the Foundation for Research, Science and Technology Contract No. C09X0504.


Heather beetle update

Simon Fowler notes beetles continued to spread over the 2009/210 summer, but not as far as predicted (or hoped).

A 5 x 5m plot sprayed to remove heather beetles as part of an impact assessment trial. Surrounding greyish vegetation is heather that's been eaten by beetles.“Last year we predicted the area of beetle-spread would increase to a total area of 36ha (conservative estimate) or 513ha (if beetle breeding really went wild). Despite the beetle population doubling in the past year it has only spread over a further 18 ha to cover 29ha in total. Life on the Central Plateau is not easy, especially if you are a little beetle without much shelter from its extreme weather moods.”

Heather beetles lay 175 eggs each on average in the UK so we expected much more rapid increases in numbers in NZ where they are largely unaffected by predators or parasitoids. In fact, the beetle population has only been roughly doubling for the last 3 years suggesting chronic poor population growth probably due to adverse climatic conditions, low foliar nitrogen levels in NZ heather and issues related with small beetle size as discussed in last year’s article. Exactly how these factors affect the population growth of the beetles e.g. whether low plant nitrogen and small body size reduces beetle egg production, or adverse climatic factors cause major larval or adult mortality, is currently being researched so we can offer mitigating strategies.

Petra Specht (DOC) & Simon Fowler (Landcare Research) looking for heather beetlesThese strategies may range from local fertilisation of release sites to promote initially strong beetle population growth to reduce the likelihood of chance events causing the extinction of small beetle populations within a few years of a release, to the option of sourcing larger body size/better climatically adapted beetles from new sites in Europe.

Observations to date support the idea that small populations of heather beetle are vulnerable to chance extinctions. While two new outbreak populations have been confirmed on the Central Plateau this season, five other small populations appear to have gone extinct. Both of the new successful outbreak populations were previously fertilized with nitrogen in 2005 and 2006. To date, we have four fertilized releases that have outperformed paired unfertilized releases, lending support to the fertiliser option.

John Mangos (NZ Army), Bruce Harvey (DOC), Paul Peterson (Landcare Research), Nicki Hughes, Harry Keys & Nick Singers (DOC) discussing future re-distribution of heather beetle. Despite what looks like a spectacular result at a few established sites, beetle populations still appear to be struggling to survive in most years on the Central Plateau but probably get lucky in some years. Getting lucky may involve getting a nitrogen boost or favourable climatic conditions during critical times during beetle development. If small populations don’t get lucky in the first 3 or 4 years after release, they seem to have a high risk of extinction.

Of the 64 releases made into high altitude Central Plateau sites between 1996 and 2007 only six (9%) have established to date (and three of these were part of an initial nitrogen addition trial). Between 2007 and 2009, a further 28 releases were made in a second, better-replicated, attempt to test the hypothesis that low nitrogen levels in heather foliage on the Central Plateau are limiting population establishment and grow. It is too early for a result from this trial.

Despite ongoing problems with poor establishment and populations growing slower than expected all is not lost. We predict current outbreak populations at high altitude Central Plateau sites probably number 3.5 - 4 million beetles (a 100-fold increase on the number we have released since 1996). Preliminary data from an impact assessement trial suggest that they are doing a good job too.

The Army have historically used herbicide to manage heather. Monitoring for impacts of heather beetle feeding and herbicide application on non-target plant species, and to see if indigenous flora will recover, is also part of this trial.

 

Contributors to the project include:

Harry Keys and Nick Singers (DOC), John Mangos (New Zealand Army), Richard Mallinson (Environment Bay of Plenty), Peter Wigley (Biodiscovery), Paul Barrett and Jens Jorgensen, Fabiana Preston (Massey University), James Shepherd, Shane Hona, Greg Arnold, Guy Forrester, Quentin Paynter, Shaun Forgie, Merilyn Merrett, Helen Harman and Lindsay Smith (currently or formerly of Landcare Research), Brent Sinclair and Caroline Williams (University of Western Ontario, Canada), Dmitry Musolin (Kyoto University, Japan) and David Renault (Université de Rennes, France). This work was funded by the Department of Conservation, the New Zealand Army and the Foundation for Research, Science and Technology Contract No. C09X0504