Report from 2016-2017

The recent visit to the UK that was generously funded by the Alma Baker Trust has been of immense value scientifically. It also permitted the creation of very useful contacts with leading grassland ecologists and biological control specialists as listed in Appendix 1. At the same time the funding provided an opportunity for me to present our current thinking on New Zealand pasture ecology. This elicited considerable interest, particularly when we compared the very notable differences in the biological control agent diversity and population densities in British pastures and their surrounds compared to the New Zealand situation. It was generally agreed that this has very significant implications in terms of New Zealand’s vulnerability to invasive species and the biological control situation. In short there was agreement that the lack of biocontrol diversity in New Zealand grasslands means that species of only passing interest in their home range can well become severe pests in New Zealand because they too, have few if any enemies. Similarly, three biocontrol initiatives have worked a thousand times better than average in New Zealand pastures. This is thought to be because there are abundant hosts(i.e. the pests) and the parasitoids also have few if any enemies of their own.

Based on this discussion, I then focused on the Argentine stem weevil story where the formerly highly effective control agent (the tiny wasp Microctonushyperodae) has lost its potency as a control agent of the weevil. The argument I put up was that the selection pressure on the weevils by the wasp has been so high that the weevil has become resistant though rapid evolution based on genetic change. This was seen to be something of a challenging idea by the various audiences I spoke to and numerous other mechanisms were suggested. Significantly however, we have in New Zealand, tested just about all of the suggested mechanisms but to no avail.

I was also able to explain further how were are now using a DNA sequencing methodology called (Genotyping by Sequencing or GBS) that uses next generation sequencing to investigate the resistance idea further by determining whether there have been any notable genetic changes in the DNA since the parasitoid was introduced. or whether there had been convergent genetic changes in those parts of New Zealand where there has been high selection pressure. Of particular value was the opportunity to discuss this in the Zoology Department at Cambridge University where it me the post-doctoral fellow Sonia Pascoal had found something very similar going on in the parasitoid intersection with crickets.

The visit to England unfolded exactly as was scheduled (see Appendix 1) and it raised the profile of New Zealand pastoral science. We had also planned visit to see Prof Dr Walter Erdelen in Germany but circumstances in the end unfortunately precluded this. Nonetheless, the opportunity arose to have dinner with Professor Sir Peter Gluckman (New Zealand’s Chief Science Adviser) in London where we discussed the purpose of this visit and its various findings.

Below are highlights of the conversations we had with the various parties that we visited.

4-5 January North Wyke, Devon.

I met Prof Phil Murray (This email address is being protected from spambots. You need JavaScript enabled to view it.)and discussed the potential for us work with him and others at the Rothamsted Sustainable Soils & Grassland Systems Department at North Wyke. I gave a seminar on the New Zealand theories outlined in Appendix 2 to the Okehampton staff and via an audio link, to Rothamsted, Harpenden. An emphasis was to contrast UK pastoral ecosystems with those of New Zealand, particularly as they pertain to biodiversity and the propensity for pest outbreaks. This extended to a discussion on how there are different and relatively independent trophic levels within the British pastoral ecosystem.

A reciprocal visit to New Zealand New Zealand was discussed.

9 January. I met with Prof Charles Godfray, (This email address is being protected from spambots. You need JavaScript enabled to view it.) Hope Professor of Entomology, Department of Zoology, Jesus College,University of Oxford. Given that he is undoubtedly one of the top biological control scientists in the world it was useful to test the ideas in Appendix 2. We also discussed Cambridge University collaboration with New Zealand and the Bio-Protection Research Centre based at Lincoln University.

On a technical basis and very briefly, we covered off the suggestion that we could collect weevils from areas where there has been little parasitoid pressure versus those where there has been high pressure and test them for susceptibility in experiments (called common garden experimentation). We also discussed looking for ‘selective sweeps’ of the genomes weevils collected from various part of New Zealand to determine whether there has been any genetic changes as a result of selection pressure. Finally, Charles discussed the usefulness of getting some data on parasitism levels and weevil ground densities.

11 January. Met with Dr Sonia Pascoal post-doctoral Fellow, Department of Zoology Cambridge University and gave a seminar on the New Zealand theories outlined in Appendix 2. This elicited considerable discussion and recognition of commonalty of her biocontrol evolution in Hawaii versus New Zealand was recognised. Of interest was the observation that the very similar rapid evolution in Hawaii and New Zealand may be because elements of island ecology occur in both locations. Dr Pascoal also provided some references to getting good quality DNA out of insects and offered to help at any time should it be required.

13 January. I made a particularly useful visit to the Game & Wildlife Conservation Trust at Burgate Manor, Fordingbridge, Hampshire and met with Drs John Holland and Nick Sotherton. I discussed in detail UK’s data-bases on British invertebrate biocontrol agents in order to compare these with what is found in New Zealand.It turned out that the Game & Wildlife Conservation Trust has compiled a most useful synopses of grassland/cereal ecosystem biocontrol biodiversity. A summary of this is given in Appendix 2 which is made up of data collected from a most useful publication entitled the ‘Encyclopaedia of pests and natural enemies in field crops’ produced by the UK Agriculture and Horticulture Development Board. This explains why the UK doesn’t get pest outbreaks of the sort we see in New Zealand. Notably, not all of the British biocontrol species are continually in UK pasture; some are located in the uncultivated hedgerows and headlands. In Britain there is real reason also to provide refugia for these spp. to bolster biocontrol when needed (hence Steve Wratten’s beetle banks). I was asked why we don’t do it New Zealand my answer was simply that if we do, not much these reserves other than native New Zealand spp. that really do not participate in our sparse pasture ecology compared to what goes on in the grassland indigenous ecosystems elsewhere.

16 January. Visited the Biology Department at York University hosted by Prof Sue Hartley and Dr Sally Howlett (This email address is being protected from spambots. You need JavaScript enabled to view it.) who is fostering collaborations between researchers, farmers, industry and other stakeholders engaged in research related to the UK N8 AgriFood programme. We discussed New Zealand pasture biology/biodiversity and the effect of silica on imparting resistance to pests. We talked further about any negative interactions between silica and phenolic defences. This is covered in Frew A. et al. (2016). Trade-offs between silicon and phenolic defences may explain enhanced performance of root herbivores on phenolic-rich plants J. ChemEcol 42: 768-771

I also spoke at length to their student Emma McLarnon who has been doing interesting work on tall fescue and how the silica gets into the plant. It is generally accepted that most (e.g. 80%) goes in via solution in water and this is thought to help plants under drought conditions. Thus uptake is increased by grazing and corresponding high levels of transpiration. In general, such uptake is presumed to incur very little metabolic cost. However, and significantly, the whole thing is not entirely passive as there is about 20% that seems to be pumped in by up- and down- regulated ‘transporter genes’. Emma discussed her transcriptomic and some proteomics work on this subject. There was also mention of a correlation between cellulose and silica levels.

Overall Sue’s Group is also conducting studies on the relationship between silica, saline and drought resistance. This has included an MSc done on wheat at the Living Systems Institute at the University of Exeter. Likewise the BBSRC Global Challenges Research Fund has supported work in Vietnam looking at the role of silica in rice. In particular this is focused on silica-imparting drought-resistance and impacts on the rice-stem borer. Conversely though, silica impacts negatively on rice straw as a forage and reduces its value as a fuel. Thus there is some thinking about minimising the amount of silica in the leaves but not in the stems.

Overall it would seem that there could good potential to look at the interaction between endophyte and silica. In particular, should high levels of silica be expressed in forage roots, it could somehow retain the small amounts of endophyte metabolites that make it into the roots.

Finally I gave a seminar on the New Zealand theories outlined in Appendix 2. There were about 30-40 people at this.

S L Goldson 20 February 2017