Robigalia Roundup LXXXVII: The rust about to be released on one of Australia's worst weeds

Hello {{first_name | Robigalia readers}},

Robigalia is back.

My husband and I welcomed our first baby nearly two weeks ago, a few weeks earlier than we'd planned for. After several complications, and a month long hospital stay, we're finally home and all healthy and well.

Between feeds and settling a newborn, we're enjoying a lot of quiet hours to just sit with him, and of course lots of chaos too!

Replies will be slower than usual for a while as we find our feet as a little family of three.

Onto some local news from Australia.

At Biosecurity Queensland's Ecosciences Precinct in Brisbane, scientists are working under quarantine to prepare Puccinia lantanae, a leaf blister rust, for release against lantana (Lantana camara), one of Australia's worst noxious weeds. Introduced from the Americas in the 1840s as a garden plant, lantana has since spread across an estimated five million hectares of pasture, bush and rainforest in NSW, Queensland, Victoria, Western Australia and the Northern Territory, costing the grazing industry more than $100 million a year in lost productivity and poisoning livestock unfamiliar with the plant.

The rust attacks lantana's leaves, shoot tips and stems, causing dieback in young growth and seedlings. The Queensland Department of Primary Industries' application to release it was recommended for approval in April, following a risk analysis testing 55 non-target plant species at CABI in the UK. The rust proved host-specific, with negligible risk to other species. Two native verbena species may show mild symptoms but aren't expected to suffer plant mortality, and grow outside the range the rust is expected to persist in.

One final approval is still needed, a "release from quarantine protocol" sign-off, before the fungus can leave the lab. Once cleared, researchers plan to spend a year building up stock to hand over to Landcare groups and councils.

Lantana thickets also serve as habitat for species such as the endangered black-breasted button-quail, so ecologists are recommending a staged approach to removal rather than an all-out assault.

Now, onto this week’s edition:

Let’s dive in!

Fusarium head blight is usually diagnosed by the time visible bleaching appears in wheat spikelets, well after the window for effective intervention has closed.

A paper by Mencarini et al., published in Plant Pathology, reports on the early biocontrol activity of Trichoderma gamsii T6085 against Fusarium graminearum in wheat spikelets, tracked through a high-throughput, multisensor imaging approach.

Working with dissected Triticum aestivum spikelets at the Finnish National Plant Phenotyping Infrastructure, the team pretreated spikelets with T. gamsii conidia 24 hours before inoculating with the pathogen. Physiological changes were then monitored every six hours for five days using three imaging platforms in parallel: chlorophyll fluorescence, RGB colour imaging, and thermal infrared.

Spikelets infected with F. graminearum alone showed measurable declines in maximum photosystem II quantum yield by 60 hours post-inoculation, before any visible symptoms appeared. Spikelets pretreated with T. gamsii held their photosynthetic activity close to uninfected controls until 108 hours, and their cumulative disease progression, calculated using the area under the disease progress curve, was within 6.4% of healthy controls. By the end of the experiment, pathogen-only spikelets had 34.1% more yellow tissue than healthy controls, compared with 14.8% in co-inoculated spikelets.

Thermal imaging showed co-inoculated spikelets consistently running warmer than pathogen-only ones, a pattern the authors interpret as active, defence-associated stomatal closure driven by T. gamsii rather than passive tissue damage.

The imaging detected biocontrol activity well before visual symptom scoring would have. The authors note that this was a detached spikelet system under controlled conditions, and image-based phenotypes are not a direct readout of fungal biomass suppression or mycotoxin accumulation, both of which require molecular validation in future field work.

In 2012, mycologists working independently in Italy and Australia each described a new fungus behind an emerging chestnut disease, giving it two different names before later work revealed they'd found the same organism. That fungus, now known as Gnomoniopsis castaneae (synonym Gnomoniopsis smithogilvyi), has since become one of the most consequential pathogens in global chestnut production.

GGnomoniopsis castaneae is an ascomycete in the order Diaporthales, family Gnomoniaceae. It persists as a symptomless endophyte in healthy bark, leaves and buds, then shifts into aggressive pathogen mode under conditions still not fully understood, a switch some researchers link to the pressures of a changing climate.

The disease it causes, chestnut brown or chalky rot, is hard to detect because of that hidden phase. A nut can look perfectly sound from the outside while its endosperm turns dehydrated, spongy and chalky white within, sometimes shot through with dark brown lesions. The fungus also causes cankers on branches and leaves, and colonises the necrotic galls produced by the invasive chestnut gall wasp, Dryocosmus kuriphilus, where it has also been found to kill the wasp itself.

Since the early 2000s the disease has spread through chestnut-growing regions of Europe and Oceania, with infection rates exceeding 80 percent of nuts reported in parts of Italy, France and Switzerland. For the mountain communities of southern Europe where chestnut cultivation has long underpinned local economies, the losses are substantial.

Management is unusually constrained. Fungicides are prohibited in chestnut forests and discouraged even in fruit groves, leaving growers reliant on sanitation pruning, tree health maintenance, and increasingly, biological control. Trunk-injected Trichoderma species have shown real promise in field trials as a chemical-free alternative.

Keep reading to meet this week's featured pathologist, Chiara Aglietti, who has worked on biological control of Gnomoniopsis castaneae.

This week, we meet Chiara Aglietti, a plant pathologist who completed her PhD in Agricultural and Environmental Sciences at the University of Florence in 2020 and has spent the five years since building a career in forest pathology, now dividing her time between diagnostic research and teaching secondary school science.

Her doctoral work centred on forest pathology, specifically the management of emerging and invasive pathogens threatening Italian woodlands. That period set the direction her research has followed since, a focus on fungal diseases affecting forest and urban trees, and on the diagnostic tools needed to catch them early.

Chestnut chalky rot, caused by Gnomoniopsis castaneae (also referred to as Sirococcus smithogilvyi or Gnomoniopsis smithogilvyi), became a particular focus, alongside pathosystems involving Dothistroma spp., Fusarium spp., and Geosmithia morbida. She also worked on biological control using Trichoderma strains, and studied how climate change is reshaping disease pressure across urban, peri-urban, and forest ecosystems.

Over her postdoctoral years she has developed, optimised, and field-tested loop-mediated isothermal amplification, or LAMP, alongside conventional PCR and real-time PCR, working to make accurate pathogen detection usable directly by people managing forests and vineyards. That focus is now being redirected toward a new problem. She is collaborating with the University of Florence on grapevine Flavescence dorée, applying methods developed in her forest pathology work to a disease with very different stakes for Italian viticulture.

Alongside her research, Chiara currently teaches biology, chemistry, and Earth sciences at an upper secondary school, and is actively looking for opportunities to return fully to research and academia. She wants to add sequencing and metabarcoding to her diagnostic toolkit, techniques she believes will help resolve aspects of these diseases that current methods still leave unclear, and she is open to new collaborations that could take her research in that direction.

If you are working on forest pathology, molecular diagnostics, or grapevine disease and think there is common ground, connect with Chiara on LinkedIn or follow her publications on ResearchGate.

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See you next Monday!

P.S. Why Robigalia? The name originates from the Ancient Roman festival dedicated to crop protection. You can read all about the history here: