WHAT’S HAPPENING WITH OLD MAN’S BEARD BIOLOGICAL CONTROL? Introduction Old man’s beard ( vitalba) has proven to be a challenging biocontrol target. Since New Zealand has many valued native Clematis species biocontrol agents need to be highly host-specific, and surveys in the native range did not yield a long list of candidates worthy of further study. Three agents have been released in New Zealand to date and a further two are currently being investigated, however one of these has been recently discounted and the other requires more in- depth study than first understood.

Landcare Research is the main science provider and programme support for biological control in New Zealand and work alongside Regional Councils and the Department of Conservation in the National Biocontrol Collective (NBC). The Collective funds and provides direction on biological control targets. This acts as a New Zealand Inc approach to funding priorities according to targets providing the greatest national good. Outside of this approach funding and resources can be sourced directly from regional councils or from the Ministry for Primary Industries Sustainable Farming Fund (SFF).

Horizons has long been a supporter of the NBC as pooled funds gain leverage; and we have also championed multiple SFF projects for tutsan and field horsetail as well as forming a funding alliance with other regional councils to advance old mans beard projects faster than relying on the national system.

Figure 1 The reality that is old mans beard; Mowhango (M.Matthewson – HRC).

\\file\herman\P\BS\03\09\Agents\OMB agents\Overview 2017.docx 24/11/17

Old mans beard biological control agents

Leaf mining fly

The first agent released, back in 1996, was a leaf-mining fly (Phytomyza vitalbae) that showed early promise, establishing readily and dispersing throughout New Zealand within a couple of years. But unfortunately it did not take long for its own natural enemies to catch up. While mining of leaves is now common on old man’s beard, six native and two exotic parasitoids, generally keep the leaf miner populations lower than the threshold needed to impact on the growth of the plant. However, damaging outbreaks do sometimes occur. Landcare Research reported heavy mining during autumn at Ashburton and on Banks Peninsula. Horizons staff have noted the leaf miner across the entire region and though occasional effects are noted there are no noticable reductions on old mans beard populations due to the leaf miner. Staff have also borne the brunt of many complaints from clematis growers angry about leaf mining of their prized clematis caused by this agent. Despite the existence of native leaf miners the publicity around this work and inability for us to identify the actual miner generally means the programme has been blamed.

Figure 2 Leaf mining fly on old mans beard (naturewatchnz).

\\file\herman\P\BS\03\09\Agents\OMB agents\Overview 2017.docx 24/11/17

Old mans beard fungus

The second agent, released around the same time as the leaf miner was believed to be a superior strain of a fungus (Phoma clematidina) already present New Zealand but only causing cosmetic damage to old man’s beard in the autumn. Large amounts of damage was observed at release sites, but this did not persist. Subsequent studies could find no trace of the released strain, and it is possible it was outcompeted by other fungi existing on old man’s beard. Studies have shown this and similar fungal complex’s to confer disease resistance to the plant.

Horizons trialled an inundative approach to fungus dispersal by using helicopter application of a spray mix of live fungus to canopy reaching plants. Though this approach was effective at delivering the pathogen to the plant the inability for the fungus to persist meant work was ceased.

Old mans beard sawfly

The third agent released was a sawfly (Monophadnus spinolae) during 1998. Although an uncommon in its native range in Europe, each larva can consume several leaves, and it was hoped that it might be able to complete three generations a year. Other sawfly species, such as the willow sawfly (Nematus oligospilus), which self-introduced to New Zealand in 1997, can be damaging pests. The old man’s beard sawfly proved to be a difficult insect to mass rear. With much perseverance in a laboratory enough were produced to make 16 field releases before the rearing colony died out. Sawflys were shipped to 14 sites from the Bay of Plenty to Otago as well as near Bulls in our region. It is thought that the rearing colony probably became too male-dominated and too inbred. If conditions are not good for mating the females produce unfertilised male eggs. Six sites quickly succumbed to floods or human disturbance and since no sign of the sawfly was seen in the field, it was thought to have failed to establish.

Figure 3 Lynley Hayes, Landcare Research, finds a sawfly in the field 2015. Image - L. Grueber(Tasman District Council)

\\file\herman\P\BS\03\09\Agents\OMB agents\Overview 2017.docx 24/11/17

Lynley Hayes from Landcare Research, along with Robin Van Zoelen and Lindsay Grueber (Tasman District Council) happened to be in the vicinity of an original release site near Nelson in January 2015 and decided to spend 15 mins searching. This site had nearly 3000 sawflies released here in 2002, by far the largest release made, and the larvae were initially covered with mesh to protect them from being eaten by birds. The site has been highly modified to provide better flood protection, and much of the old man’s beard had been removed to make space for native plantings, so the trio’s expectations were low. However, clumps of old man’s beard remain at the site and Lynley discovered one of the distinctive white caterpillar-like larvae on the second clump examined. However, two hours of searching only yielded another two larvae and one adult, so the sawflies remain rare at this site. Reasons for the low population may be that it is inbred or taking a hit each year from wasps.

The merits of having another attempt at establishing the sawfly have since been considered, given the ongoing seriousness of the old man’s beard problem in many regions. Before investing in such an undertaking, it was agreed that all release sites should be checked once more at the optimal time of the year. Given the proven ability to establish, and the questions around the sex ratio of the initial releases, a new project has begun to have another attempt at establishing the sawfly. We can’t rule out that predators, like wasps, are the problem, although a study has shown that sawfly larvae readily expel haemolymph as an anti-predation defence (referred to as “easy bleeders”) which is toxic to ants, killing them in 1-2 days.

Figure 4 Digging for sawfly pupae in Serbia; back in the Christchurch facility. (Landcare Research)

\\file\herman\P\BS\03\09\Agents\OMB agents\Overview 2017.docx 24/11/17

This means that further efforts to attempt to establish the sawfly are warranted, especially following the discovery of another European publication indicating this agent causes severe defoliation twice a year in Serbia. Landcare Research travelled to Serbia in July 2017 to oversee mite testing and to collect some second generation sawflies. Host-testing has confirmed that Serbian sawflies have the same host-range as the populations originally tested which originated from different parts of Europe. The sawfly pupae were being held in the Lincoln containment facility but it appears the harvest technique used to dig out the soil borne pupae has contributed to the loss of all pupae. Another attempt using different methodology to collect more sawflies from the first generation in 2018 (May/June), as they appear to be more numerous at this time of the year. The idea is to ensure the founding populations are larger this time, with an initial location being close to Lincoln to better enable intensive monitoring. The NBC discussed where the best site would be to release the sawflies. The only site where sawfly is present currently (near Nelson) is highly modified and was agreed to not be ideal. For convenience it was agreed to find a good, secure site in Canterbury, since there could be many trips required by Lincoln-based staff to add material to the site and assess progress.

Old mans beard bark

A (Xylocleptes bispinus), known to regularly kill old man’s beard vines in Europe, was investigated by scientists at CABI in Switzerland during the 1990s, but proved difficult to test. The testing was discontinued without resolution due to a lack of funding. When the NBC showed renewed interest in this agent, a field trial in the native range was deemed the way to go. However, attempts to set up such a field trial in the UK proved much more difficult than expected as New Zealand native Clematis test plants failed to thrive due to the cooler climate, severe storms and even rabbit browsing. More recently arrangements were made with a botanical garden on the Isle of Wight which offers a milder climate and has native populations of the bark . However establishing the plants proved to be quite challenging. Native Clematis plants from New Zealand typically seem to struggle in the first year to adapt to the Northern Hemisphere and some plants die. Those that survive continue to do poorly in the second year and then become established in the third. To ensure that all the test species were available in sufficient numbers, it was necessary to end over several shipments of replacement plants.

Figure 5 Bark beetle attacking Clematis forsterii. (Landcare Research)

\\file\herman\P\BS\03\09\Agents\OMB agents\Overview 2017.docx 24/11/17

Due to the challenges with growing on healthy test plants, it became clear in 2016 that the field trial would need to run for at least another 3–4 years before it could be assessed, and that we would need to have some luck on our side for no further plant losses to occur. At this point it was agreed that with Landcare Research’s newer, better containment facilities, it was probably worth importing a shipment of the beetles and undertaking some studies here on whole plants. Even if the tests could not resolve the specificity question they could complement and assist with interpretation of the field trial results, and provide an opportunity to learn more about how to rear and work with this insect. Some additional funds were secured from the councils most seriously affected by old man’s beard (championed by Horizons) that allowed the work to progress, and the results proved to be very clear cut.

Figure 6 Importation of a colony of the bark beetle (Xylocleptes bispinus) was able to demonstrate conclusively that it is not suitable to release in New Zealand. Field trials in the UK have now been discontinued

The bark beetle was able to inflict the same levels of damage on Clematis foetida, C. quadribracteolata, C. mārata, and C. forsterii as it does on old man’s beard, in many instances totally severing stems, laterals and petioles. Even if the beetles are behaving slightly abnormally indoors, the risk of non-target damage is therefore unacceptably high, and so the beetle must be rejected as a potential agent. The colony imported for testing has been culled and the field trials have been discontinued. This result was very disappointing to Horizons staff, those other regional councils who helped fund the project and indeed a very wide pool of people holding onto hope that this agent would inflict significant damage to old mans beard.

\\file\herman\P\BS\03\09\Agents\OMB agents\Overview 2017.docx 24/11/17

Leaf and bud galling mite

The last known untested biological control option is a leaf and bud galling mite (Aceria vitalbae) not found during the original agent surveys that only came to light more recently. The mite stunts the new growth and is likely to be highly host-specific. However, again a range of unexpected setbacks to studying this agent occurred, which have only recently been overcome. Several attempts to establish a mite colony in Landcare Researchs containment facility at Lincoln were unsuccessful after shipments were delayed in transit or heavily diseased. A mite expert from the University of Belgrade, Serbia, hand-delivered a colony of mites but plant quality issues then emerged that could not be treated without harming the mites and the colony was lost. The narrow window in which mites can be collected in the field further complicated matters. At that point it seemed more feasible to attempt the host-testing in Europe.

Figure 7 Host testing involves pinning galls infested with mites onto test plants. (Landcare Research)

The logistics of shipping the test plants to Serbia took some time to work through. However, in 2015/16 testing of five New Zealand native Clematis species (C. foetida, C. afoliata, C. paniculata, C. quadribracteolata, and C. petrei) was successfully completed with no sign of attack. Testing of three additional native and five ornamental Clematis species was then undertaken in 2016/17, but produced some unexpected results. When the trials were assessed after 60 days (which involves destructively sampling the test plants so they can be examined under a microscope) the mites were persisting, without causing symptoms, on C. forsteri, C. mārata, and C. marmoraria x petrei and, unlike the previous year, also on C. afoliata. The mites were also persisting and causing symptoms on three of the ornamental species (C. stans, C terniflora, and C. montana), although it is not known to be a pest on ornamental Clematis in Europe. This raised questions about whether there could be identity issues with the mite, and this is currently being explored via molecular studies. Mites are also notorious for sometimes persisting for weeks or even months, but doing no harm during trials on test plants which prove to be non-hosts in field conditions. In a natural setting they would likely be eliminated by predators which they are not exposed to in the lab. So the tests need to be repeated, and with additional replicates, so that some can be allowed to run for longer to see how long the mites continue to persist. If these tests confirm that attack on native Clematis is likely then the mite will have to be rejected. However, if it turns out that only some attack on some ornamental species is likely, what this means for the project is a little less clear cut. An economic analysis of the

\\file\herman\P\BS\03\09\Agents\OMB agents\Overview 2017.docx 24/11/17 benefits of ornamental Clematis species in New Zealand, compared with the costs of old man’s beard, may indicate whether the mite should still be pursued further.

Horizons are the sponsoring council presenting this project on behalf of the NBC through to the EPA. As the potential for the effects of this agent seem wider than a truly host specific agent it would be reasonable to expect submissions against the introduction from a number of parties.

Figure 8 Bud gall forming mite (Aceria genistae) testing in Serbia is continuing

Conclusion

Horizons eagerly awaits the results of the bud gall forming mite host testing and any possibility for release as soon as possible, as well as developments with the saw fly re-establishment.

We will continue to put a case for expiring all available options of biological control against old mans beard.

\\file\herman\P\BS\03\09\Agents\OMB agents\Overview 2017.docx 24/11/17