Finding a Perfect Match
Our project to develop biocontrol for pampas (Cortaderia spp.) has thrown up a few surprises.
We initially planned to survey for potential biocontrol agents in Argentina, the only place in South America where both Cortaderia selloana and C. jubata were reported to occur. It did not take long to discover that taxonomic treatments can be problematic for identifying pampas, and there was a danger of looking at the wrong material. Molecular analysis quickly showed that C. jubata from Argentina was different to material in New Zealand of the same name. However, we were able to match New Zealand C. jubata with material in southern Ecuador, and Dr Maria Eugenia Ordonez and Dr Charlie Barnes (Pontificia Universidad Católica del Ecuador) have now undertaken two surveys for us there. A similar suite of fungi have been found on C. jubata in both countries. Unfortunately in the native range the plants also generally appear to be quite healthy, and only a black smut (Ustilago sp.) that damages the flowerheads is showing any potential as a biocontrol agent.
Finding a match for Cortaderia selloana has been much trickier. We struck out a second time with samples from Argentina, apart from two small infestations of pampas in Nelson and Southland, which were genetically different to C. selloana in the rest of the country. “We recommended these infestations should be eradicated as they represent a third pampas entity for New Zealand,” said Gary Houliston. Recently we found more samples with some similarity to Argentinean pampas, growing in Auckland, that appear to be intermediate between the other two C. selloana entities in New Zealand. We have requested more pampas samples from Northland, Bay of Plenty, Waikato, and other parts of Auckland, to check if this material is widespread. If this proves to be the case then the project will have to take this into account.
Having ruled out Argentina as the source of the most common New Zealand genotype we looked next in neighbouring Uruguay. Dr Carlos Villamil (Universidad Nacional del Sur, Argentina) again collected and shipped samples to us, but they were also not the match we were hoping for. With the help of Dr Hernan Norambuena we then focused on Chile. In a small stroke of luck we found a perfect match for New Zealand material at a site where a handful of pampas plants had been deliberately planted next to a soccer field. But where had these plants come from? Fortunately Hernan was able to track down the man responsible for the planting 20 years earlier. Hernan then visited the source of these plants and collected further samples, which we have confirmed are the same. Further sampling around the two hotspots has provided further matches, and surveys for potential biocontrol agents can now get underway in earnest this spring. For the sake of completeness we will also check material from Brazil collected by Professor Henrique Pedrosa Macedo (University of Parana).
In additional to our classical biocontrol approach, Stan Bellgard is exploring whether the utility of synthetic and organic herbicides can be increased through co-formulation with a plant pathogen (Nigrospora oryzae) recovered from pampas. This could potentially allow the rates of herbicides used, and non-target damage, to be reduced and initial results are promising. Plants treated with Greenscapes® (formulated from “fatty acid”) died back initially, but resprouted after a month. Half of the plants were then treated with Nigrospora, which caused a significant reduction in growth. “Plants treated with just Nigrospora and water also had 50% less shoot biomass than those just treated with water, showing that Nigrospora can potentially have a useful impact on its own,” said Stan. This work to beat pampas will be continuing, along with research in at least three South American countries, this spring.
This project is funded by the National Pampas Biocontrol Initiative through a grant from the Ministry for Primary Industries’ Sustainable Farming Fund (11/049), supported by a number of co-funders, including the National Biocontrol Collective.