Between 2023 and 2024, researchers collected dead and decaying twigs bearing fungal fruiting bodies from macadamia plantations in Yunnan Province in southwestern China and Chiang Mai Province in northern Thailand. These two regions are significant for different reasons. China first introduced macadamia in the 1970s and now accounts for more than 60 percent of the world’s cultivated macadamia area, with Yunnan alone representing 88 percent of that national footprint, making it the largest macadamia-growing region on Earth. Thailand, where the crop was trialed experimentally as early as 1953, has seen rapid expansion of plantations in the north, particularly around Chiang Mai, as domestic consumption and export potential have grown.

Back in the laboratory, the team combined classical morphological examination with modern molecular systematics to work out exactly what they had collected. Under compound and stereomicroscopes they documented the fine details of fungal anatomy: the size and shape of the flask-like fruiting bodies known as ascomata, the layered structure of their walls, the form of spore-producing sacs called asci, and the dimensions, septation, and surface texture of the ascospores themselves. For the molecular work, DNA was extracted from pure cultures, and six genetic loci were amplified and sequenced, including the internal transcribed spacer region (ITS), the nuclear large and small ribosomal subunits (nrLSU and nrSSU), and the protein-coding genes tef1-α, tub2, and rpb2. These sequences were aligned, combined, and analyzed using maximum likelihood and Bayesian inference methods, generating phylogenetic trees for each fungal genus with strong statistical support at the critical nodes.

The results were striking. Eighteen fungal taxa were identified across ten genera and seven families, all within the phylum Ascomycota. Five of these proved to be new to science: Dothiorella lignicola, Lasiodiplodia macadamiae, Palmiascoma macadamiae, Xylochrysis macadamiae, and Xylochrysis yunnanensis. Each was formally described and named according to the International Code of Nomenclature for algae, fungi, and plants, with type specimens deposited in herbaria in China and Thailand and living cultures preserved in culture collections. In several cases, the new species were separated from their closest relatives by a combination of subtle morphological differences and substantial genetic distances. Xylochrysis macadamiae, for example, differs from its nearest known relatives in having larger, semi-immersed fruiting bodies and rough-walled ascospores, along with nucleotide differences of around 7 to 12 percent in key gene regions.

Thirteen previously described species were also recorded from macadamia for the first time, spanning genera such as Sporidesmium, Crassiparies, Chromolaenicola, Montagnula, Pseudochaetosphaeronema, and Helminthosporium. Several of these records were also new geographic findings, extending known distributions across national borders. Perhaps most intriguingly, the sexual reproductive structures of three species, Chromolaenicola ananasi, Pseudochaetosphaeronema siamense, and Helminthosporium nanjingense, had never been observed before; this study documented them for the first time, filling significant gaps in mycological knowledge. Eight of the ten genera encountered had never previously been reported from macadamia anywhere in the world.

One species had a tangled taxonomic backstory. Dothiorella lignicola had been described earlier under a different name, but that earlier name was formally rejected because its original description was based on an incorrect host, species name, etymology, and DNA sequences, a violation of Article 52.1 of the nomenclatural code. The replacement name D. lignicola, referring to the fungus’s wood-dwelling habit, now stands, anchored by a Thai collection whose tef1-α gene sequences differ from its closest relatives by more than 20 base pairs, alongside consistent morphological distinctions such as larger, ovoid conidia.

Identifying the fungi was only half of the study. Because saprobic fungi survive by secreting enzymes that dismantle tough plant polymers, the researchers wanted to know what these macadamia colonizers could actually digest. Twenty pure cultures representing the 18 species were screened on agar plates for four lignocellulolytic enzymes: cellulase, xylanase, mannanase, and laccase. For the first three enzymes, plates containing carboxymethyl cellulose, xylan, or locust bean gum were flooded with Congo red after incubation; where enzymes had broken down the substrate, a clear halo appeared around the fungal colony. Laccase activity was detected instead on guaiacol agar, where the enzyme oxidizes the compound to produce a brownish-red color change. Enzyme output was quantified with an enzyme potency index, calculated from the difference between the halo diameter and the colony diameter, and all experiments were run in triplicate with statistical analysis by one-way ANOVA and Duncan’s multiple range test.

The enzyme screening revealed a community of capable biomass degraders, but with clear patterns of specialization. Xylanase was the most frequently detected activity, produced by 17 isolates representing 15 species, followed by cellulase, found in 14 isolates from 12 species, and mannanase, found in 10 isolates from nine species. Laccase, the oxidative enzyme needed to attack the chemically stubborn lignin fraction of plant cell walls, appeared in only five isolates. The single strongest xylanase producer was the newly described Xylochrysis macadamiae, with an enzyme potency index of 3.50, followed by Sporidesmium tropicale at 3.10. In the cellulase category, two Helminthosporium species dominated, with H. puerense reaching an index of 2.25. Mannanase activity peaked in Pseudochaetosphaeronema puerense at 1.98, while Sporidesmium tropicale led laccase production at 2.20. Only three isolates, Dothiorella lignicola and two Lasiodiplodia species, showed no detectable activity for any enzyme, possibly because their enzyme production fell below the assay’s detection limit or because they preferentially consumed simple sugars available in the medium.

The predominance of xylanase makes ecological sense. Hemicellulose, the xylan-rich matrix that surrounds cellulose fibers in plant cell walls, is less crystalline and more chemically accessible than cellulose itself, so decomposer fungi typically attack it first, gaining access to the more recalcitrant components afterward. Lignin, encrusted around the cellulose in hardwood twigs, requires specialized oxidative enzymes such as laccases and peroxidases, which relatively few ascomycetes produce in quantity. The observed enzyme profile of the macadamia community mirrors this well-known decomposition sequence, and the four isolates that produced all four enzymes tested, including Crassiparies quadrisporus, Pseudochaetosphaeronema chiangraiense, and Sporidesmium tropicale, stand out as particularly versatile degraders.

Beyond their ecological role in recycling carbon, nitrogen, and phosphorus through decaying orchard wood, these fungi have potential commercial value. Lignocellulolytic enzymes are workhorses of industrial biotechnology, used in converting plant biomass to biofuels, in food and feed processing, in pulp and paper manufacture, in textile production, and in environmental bioremediation. The authors suggest that the next steps should include quantitative enzyme assays, optimization of culture conditions, and purification and biochemical characterization of the most promising enzymes. For now, the study’s core message is clear: even beneath one of the world’s most intensively studied nut crops, entire communities of fungi, including species unknown to science, have been quietly waiting on dead twigs, and some of them carry enzymatic toolkits worth far more than their weight in nuts.

Subject of Research: Diversity, taxonomy, and lignocellulolytic enzyme production of saprobic microfungi associated with macadamia in China and Thailand

Article Title: New species and additional records of saprobic microfungi associated with Macadamia in China and Thailand and their lignocellulitic enzyme production

Article References: Zhang, X., Karunarathna, S. C., Tibpromma, S., Senwanna, C., Kumla, J., Du, T.-Y., Elgorban, A. M., Alfagham, A. T., Filimban, F. Z., Dai, D.-Q., & Suwannarach, N. (2026). New species and additional records of saprobic microfungi associated with Macadamia in China and Thailand and their lignocellulitic enzyme production. MycoKeys, 141, 217-281. https://doi.org/10.3897/mycokeys.141.209886

Image Credits: AI Generated

DOI: 10.3897/mycokeys.141.209886

Keywords: macadamia, saprobic fungi, new species, taxonomy, phylogenetics, lignocellulolytic enzymes, xylanase, cellulase, laccase, biotechnology, China, Thailand

The macadamia is not an ordinary crop. Labour-intensive harvesting and complex post-harvest processing make it one of the costliest nuts in the global market, which means that every percentage point of yield lost to insects translates into substantial economic damage. Protecting the trees from pests is therefore a central concern for growers, and the conventional response has often been intensive chemical or mechanical intervention. The new research suggests that an alternative, ecologically grounded strategy may already be flying overhead every night. By examining how natural vegetation in and around plantations shapes the communities of birds and bats that forage among the trees, the team set out to quantify the pest control services these animals provide and to identify the landscape features that sustain them.

The study was conducted at ten intensively managed macadamia plantations in South Africa, a design that allowed the researchers to capture variation in both management intensity and surrounding land cover. At each site, the team compared trees growing at the edge of the plantation with trees in the centre, a comparison specifically chosen to analyse the influence of the surrounding vegetation on the animals visiting the crop. Edge trees sit closer to hedgerows, forest fragments and other natural features, while central trees are embedded more deeply within the monoculture, so any systematic differences in pest damage or animal communities between the two positions can reveal how strongly the wider landscape shapes what happens inside the orchard.

Surveying the fauna required two very different techniques. The researchers recorded 111 bird species through direct observation, walking the orchards and documenting the birds foraging among the trees. Bats, being nocturnal and difficult to observe visually, were detected through their echolocation calls, which were captured with acoustic recording equipment and used to identify 16 species. This acoustic monitoring allowed the team to build a detailed picture of which bat species were active over the plantations, how their activity varied between sites, and how that variation related to the structure of the surrounding landscape and the level of insect damage measured on the nuts.

The results pointed clearly to bats as the dominant pest control agents in the system. Bat activity was associated with reduced insect damage, and this effect was particularly pronounced in plantations that contained less natural habitat within their boundaries or were surrounded by natural habitat in the wider landscape. Natural habitat, in the sense used by the researchers, includes native forests, bushland and scrubland, the heterogeneous vegetation types that provide roosting sites, foraging grounds and refuge for insectivorous bats. In landscapes where these features persisted, the bats appeared to compensate for the scarcity of on-farm natural cover, patrolling the orchards and suppressing the insect populations that would otherwise feed on the developing nuts.

To test the contribution of flying vertebrates directly, the team conducted exclusion trials, a classic experimental approach in which nets are used to keep birds and bats away from the trees. The outcome was striking. When birds and bats were excluded, the proportion of nuts damaged by insects rose from 6.2 per cent to 10.7 per cent, an increase of roughly 70 per cent. This experiment provides some of the most direct evidence that these animals deliver a measurable, economically meaningful service to macadamia growers. Intriguingly, however, the researchers could not demonstrate a direct influence of bird numbers on pest infestation, suggesting that in this system the nocturnal bats, rather than the diurnal birds, carry the primary burden of biological pest control.

The landscape context proved to matter in more ways than one. As the proportion of natural habitats around the plantations increased, not only did the number of bats rise, but their diversity increased as well, indicating that intact vegetation supports a richer community of these aerial predators rather than merely a larger one dominated by a few generalist species. Even the yield of the macadamia trees was linked to the share of natural habitat in the landscape, reaching its highest level when natural habitats accounted for around 60 per cent of the surrounding area. This peak suggests a non-linear relationship in which a substantial but not exclusive share of natural cover best supports the ecological processes, from pest suppression to pollination, that underpin crop production.

Bird communities, by contrast, responded to fine-scale structure within the plantations rather than to the broader landscape. The researchers found that the species assemblages differed between the edges and the centres of the orchards: species that prefer dense and woody vegetation were more common at the plantation edges, while species of open habitats predominated in the interior. This edge-to-centre gradient shows that even within a single intensively managed plantation, the arrangement of vegetation creates distinct niches for different bird species, and it hints that the conservation value of an orchard depends not only on what surrounds it but also on how its own internal habitat mosaic is structured.

The implications extend well beyond macadamia. Lead author Dr Mina Anders of the Department of Functional Agrobiodiversity and Agroecology at the University of Göttingen emphasised the broader message of the findings. Natural habitats, she explained, are valuable refuges that support beneficial organisms providing pollination and pest control, which in turn benefits agricultural production and the farmers who depend on it. It is therefore essential, she argued, that natural habitats and their conservation are incorporated into the planning of agricultural land. In other words, the patches of native forest, bushland and scrubland that persist between and around fields should not be viewed as idle or expendable land, but as functional infrastructure that actively contributes to farm productivity.

For a crop as valuable as the macadamia, the economics of this ecological service are compelling. A 70 per cent increase in insect-damaged nuts when bats and birds are excluded illustrates how quickly quality, and with it market value, deteriorates without these natural allies. The study thus highlights a form of agriculture that combines biodiversity with production, in which conserving natural vegetation within and around farmland is not a concession to environmental ideals but a practical investment in yield and nut quality. As global demand for macadamias continues to grow, the research offers growers and land-use planners a concrete, evidence-based reason to protect the forests and scrublands that shelter the bats working the night shift over South Africa’s orchards, and it adds macadamia plantations to the growing list of cropping systems where the fate of the harvest is quietly tied to the health of the surrounding landscape.

Subject of Research: The role of bats, birds and natural habitat in biological pest control in macadamia orchards

Article Title: Bats as a form of biological pest control

Article References: Bats as a form of biological pest control. (n.d.). Original publication

Image Credits: AI Generated

DOI: Not provided

Keywords: bats, biological pest control, macadamia, South Africa, agroecology, natural habitat, biodiversity, bird communities, echolocation, crop yield, landscape management, University of Göttingen