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Pest/Pathogen of the Month: June

Scientific name: Rosellinia necatrix

Common names: White root root

Rosellinia necatrix Berl. ex Prill. is the causal agent of white root rot on various plant species, including almond, apple, peach, orange, pear, grape, coffee, olive and avocado. The genus Rosellinia consists of multiple species capable of causing disease, however, R. necatrix is the most widely distributed and devastating. R. necatrix was first identified in South Africa in 1974 on apple and pear trees in the Western Cape. It is an ascomycete, saprophytic pathogen that causes rotting of the roots and collapse of host conducting vessels leading to wilting and death. This fungus is soilborne and can survive in the soil on woody debris and organic matter for long periods of time. White root rot is difficult to diagnose since foliar and root symptoms are unspecific, therefore, the disease is often mistaken for Phytophthora root rot. Some hosts do not show any foliar symptoms until the plant suddenly dies, sometimes with fruit and leaves still attached to the tree. A distinguishing symptom is the presence of white mycelial growth on the root surface, in the soil and underneath/on top of the bark at the crown of the tree. Disease control options are limited due to the pathogen’s hardy resting structures, extensive soil penetration and ability to withstand drought, acidic soils and many common fungicides.

 

 

Pest/Pathogen of the Month: April

Scientific name: Bathycoelia distincta (old name: B. natalicola - distant)

Common names: Two-spotted stink bugs

Bathycoelia distincta is a Heteropteran that was discovered in 1984 in the Limpopo region (South Africa). This indigenous species belongs to the Pentatomidae family, well-known to comprise the highest number of economically important species in the world.  These bugs are phytophagous and feed by inserting their stylets (mouthpart) into the food source to suck up nutrients, resulting in potential damage to plant tissue. Pentatomidae species are also characterized by their general ovoid form, antennae, and tarsi segmented into five and three parts respectively, and a short triangular scutellum. They are commonly called stink bugs, due to the odour produced by their scent glands. The Pentatomidae is the largest family within the superfamily Pentatomoidea (Heteroptera suborder, true bugs) and comprises of approximately 5000 of the estimated 8000 species, followed by the Lygaeidae, Reduviidae and Miridae. Species within Pentatomidae are further divided into eight subfamilies namely: Asopinae, Cyrtocorinae, Discocephalinae, Edessinae, Phyllocephalinae, Podopinae, Serbaninae and Pentatominae (the largest), in which B. distincta belongs.

Pest/Pathogen of the Month: May

Scientific name: Pectobacterium

Common names: Soft rot bacteria; Soft Rot Enterobacteriaceace

Pectobacterium species, formerly known as Erwinia species, are the main causal agents of soft rot, blackleg and aerial stem rot of potatoes as well as of many other vegetables and ornamentals (Figure 1). The genus consists of many species capable of causing disease. It is a Gram-negative, opportunistic pathogen that causes tissue maceration through the production of pectinolytic enzymes that result in cell wall degradation. The pathogen is mainly spread by latently infected propagation material, although it can also be spread by contaminated irrigation water, equipment and insects. It isn’t soilborne and therefore doesn’t overwinter or survive in the soil for longer than six months in the absence of a host. The pathogen remains latent within the plant until favourable environmental conditions cause a shift from latency to disease development.  Symptom expression is dependent on quorum sensing and therefore, pectinolytic enzyme production only starts after the pathogen population reaches a critical threshold. The main environmental factor that promotes disease development is high soil moisture, which creates an anaerobic environment, favouring the growth of this facultative anaerobe.

Pest/Pathogen of the Month: March

Scientific name: Pseudomonas syringae

Common names: 

I assure you, there is nothing fake about Pseudomonas syringae, so named after its host of origin, Syringa vulgaris commonly known as lilac, or its devastating effect on agricultural systems. P. syringae is listed as #1 in the top 10 most economically significant plant pathogenic bacteria1. This bacterium is known as a species complex that comprises nine genomospecies (DNA-DNA hybridization delimitation), 13 phylogenetic groups (sequence-based similarity of four housekeeping loci), and 19 phylogenomic groups (whole-genome based phylogeny). There are currently over 60 pathovars (strains characterized based on host of origin or similarity of symptoms caused). P. syringae is widely used as model pathogen to study bacterial pathogenesis, molecular mechanisms of plant-microbe interactions, microbial ecology, as well as evolution and epidemiology.

New Publications

Botha I, Maduna SN, Hagen SB, Lall N, Berger DK. (2026) 3RAD-Guided SNP Discovery for Species Identification and Conservation of the Medicinal Southern African Tree Genus Greyia Hook. & Harv.. Ecology and Evolution 16(5):e73412, 1-29. 10.1002/ece3.73412
Wingfield BD, Coetzee MPA, Wingfield BJ, Groenewald M, Pohl C, Wingfield MJ. (2026) The genetic blueprint of Cyclohexamide resistance: Analysis of 816 yeast species. Research Square 10.21203/rs.3.rs-9313202/v1
Paap T, White D, Bose T, Burgess TI. (2026) Diversity and phylogeny of Phytophthora Clade 9, including descriptions of three novel species. Mycological Progress 25:29. 10.1007/s11557-026-02140-4
Li GQ, Slippers B, Wingfield MJ, Chen SF. (2026) Diversity, distribution and host range of Botryosphaeriaceae in China. Forest Pathology 10.1111/efp.70077
Joubert M, van den Berg N, Theron J, Swart V. (2026) Leaf bleaching is associated with extensive transcriptional reprogramming in avocado trees with sunblotch disease. Virology 620:110903. 10.1016/j.virol.2026.110903 PDF
Nzuza P, Schroder ML, Slippers B, Maes WH. (2026) Spectral responses to larval and artificial defoliation in Eucalyptus dunnii: Implications for UAV-based detection of Gonipterus damage. Drones 10(4) 10.3390/drones10040250
Six DL, Marincowitz S, Duong TA. (2026) Ophiostoma ipsi-confusi sp. nov. Six, Marinc. & Duong, a consistent symbiotic fungus of the pinyon ips bark beetle, Ips confusus LeConte. Symbiosis 10.1007/s13199-026-01135-9
Yan Z, Zhao Y, Meng X, Gao M, Si H, Zhao G, Bose T, Chang R. (2026) New manganese-oxidizing Acremonium-like fungi from halophytic rhizospheres in the Yellow River Delta, China. Mycologia :1-13. 10.1080/00275514.2026.2627133
Eshetu FB, Barnes I, Nahrung HF, Fitza KNE, Slippers B. (2026) A Century of invasion: How biosecurity influenced populations of Sirex noctilio and Its fungal symbiont in Australasia. Molecular Ecology 35(6):0962 - 1083. 10.1111/mec.70311
Viljoen A, Duong TA, Kanzi AM, Wingfield BD. (2026) Comparative analysis of mitochondrial genomes in the Ceratocystidaceae reveals highly conserved gene organization despite substantial genome size variation. BMC Genomics 10.1186/s12864-026-12755-2
Ribeiro MF, Cavallini G, Solce GN, Favoreto AL, De Souza Passos J-R, Barbosa LR, Hurley BP, Wilcken CF. (2026) Cold storage of Gonipterus platensis (Coleoptera: Curculionidae) eggs for Anaphes nitens (Hymenoptera: Mymaridae) rearing. PeerJ :1-14. 10.7717/peerj.20903 PDF
Pham NQ, Marincowitz S, Marpaung YMAN, Tarigan M, Wingfield BD, Wingfield MJ. (2026) Two Cryphonectriaceae species from Eucalyptus leaves in North Sumatra and their stem inoculation outcomes. Fungal Systematics and Evolution 17:69–79. 10.15761/fuse.2026.17.05 PDF
Nickles GR, Stokes CK, Narh DL, Lynn KMT, Fuqua SR, Bryan C, Allen BM, Bivins CP, Bok JW, Brewer JS, Buthelezi ST, Clark JPRM, Coon KL, Corby LR, Coetzee MPA, Dewing C, Duong TA, Harris MA, Keller NP, Kopotsa K, Lane FA, Nichols HL, Nieuwoudt A, Nuñez MA, Medina Munoz ME, Park SC, Pham NQ, Ryan KT, Solís M, Vilgalys R, Wallace JM, Wang YW, Wingfield BD, Wingfield MJ, Worley TK, Zallek TA, Zamanian M, Hoeksma JD, Drott M, Pringle A. (2026) Equipped for success: Genomes and metabolites of the European Amanita muscaria are conserved in its novel South African range. New Phytologist 10.1111/nph.71064
Pham NQ, Wingfield MJ, Duong TA, Wingfield BD. (2026) Draft genome sequence of Elsinoe masingae: the causal agent of Eucalyptus scab in South Africa. Australasian Plant Pathology 55:37. 10.1007/s13313-026-01082-5
Pham NQ, Marincowitz S, Wingfield BD, Crous PW, Santos SA, Durán A, Tarigan M, Wingfield MJ . (2026) Pseudoteratosphaeria supramediana sp. nov. (Teratosphaeriaceae, Mycosphaerellales), a new foliar pathogen on Eucalyptus in Indonesia. Australasian Plant Pathology 55:28. 10.1007/s13313-026-01092-3
Nel WJ, Jali S, Barnes I, Wondafrash M, Hurley BP. (2026) Outbreaks of a native jewel beetle, Agrilus grandis (Coleoptera: Buprestidae), on commercial black wattle, Acacia mearnsii, plantations in South Africa. African Entomology 34(1):1-5. 10.17159/2254-8854/2026/a24625
Postma A, Klynsmith L, Duong TA, Allison JD, Smidt W, Waterhouse RM, Lesny P, Oeyen JP, Petersen M, Martin S, Liu S, Zhou X, Ziesmann T, Donath A, Mayer C, Misof B, Niehuis O, Peters RS, Podsiadlowski L, Coetzee MPA, Joubert F, Slippers B. (2026) Genome and transcriptome-based identification and expression profiling of chemosensory gene families across developmental stages and tissues in Sirex noctilio (Hymenoptera: Siricidae). Insect Molecular Biology :1-14. 10.1111/imb.70029
Aylward J, Visagie CM, Roets F, Wingfield BD, Wingfield MJ. (2026) Genome analyses reveal two novel species of Seiridium from Acacia mearnsii. Mycological Progress 25:8. 10.1007/s11557-026-02121-7
Liu QL, Wingfield MJ, Duong TA, Wingfield BD, Crous PW. (2026) Taxonomy, distribution and dispersal of Calonectria species: Important pathogens of forestry, agricultural and horticultural crops. Current Forestry Reports 12(4) 10.1007/s40725-025-00262-8
Nethononda PD, Hurley BP, Slippers B, Makhura MN. (2026) Smallholder farmers’ knowledge, perception and management of Spodoptera frugiperda (Lepidoptera: Noctuidae) on Zea mays at irrigation schemes in Limpopo province, South Africa. Crop Protection :107457. 10.1016/j.cropro.2025.107457
Swanepoel S, Naidoo S. (2026) A weighted gene co-expression network analysis characterises the common defence responses of Eucalyptus to diverse biotic challenges. Scientific Reports 16:5387. 10.1038/s41598-025-32699-z
Addikah C, Abubeker H, Mukiibi A, Bairu M, Amelework A, Van der Laan M, Mangani R. (2026) Current and future potential of cassava (Manihot esculenta) in Southern Africa: a scoping review. 4:120. 10.1007/s44279-026-00598-0
Botha I, De Canha MN, Oberlander K, Botes J, Lall N, Berger DK. (2025) DNA barcoding and anti-tyrosinase activities of three species-representative populations of the genus Greyia Hook & Harv. South African Journal of Botany 189:55-67. 10.1016/j.sajb.2025.11.035
Thomas C, Wilken PM, Coetzee MPA, Visagie CM. (2025) Advancing the taxonomy of Sclerotinia (Helotiales, Sclerotiniaceae): a review and recommendations for an important plant-pathogenic genus. IMA Fungus 17:e175737. 10.3897/imafungus.17.175737
Townsend G, Hill M, Hurley BP, Nel WJ, Crous C, Roets F. (2025) First report of the ambrosia beetle, Amasa parviseta (Curculiondae: Scolytinae), in South Africa. African Entomology 10.17159/2254-8854/2025/a24167 PDF
Roux J, del M Angel L, Barnes I. (2025) First report of the eucalypt stem canker pathogen Teratosphaeria gauchensis in South Africa. New Disease Reports 52(2):e70091. 10.1002/ndr2.70091
Nel WJ, Barnes I, Jali S, Impson F, Oberprieler RG, Hurley BP. (2025) First report of Melanterius inconspicuus (Coleoptera: Curculionidae: Cleogonini) from KwaZulu-Natal, South Africa, with observations of its development in black wattle. Southern Forests 10.2989/20702620.2025.2537823 PDF
Regasa K, Beze W, Anjulo A, Wondafrash M, Hurley BP, Lawson SA, Healey M, Germishuizen I. (2025) Evaluating fungicides for the management of rust (Uromycladium acaciae) on black wattle nursery seedlings in Awi zone, Amhara regional state, Ethiopia. International Journal of Forestry Research 10.1155/ijfr/5547814
Ramantswana TM, Malatji DP, Pierneef RE, Soma P, Van Der Nest MA, Muchadeyi FC. (2025) Differential gene expression analysis of Dohne Merino sheep naturally infected with Haemonchus contortus. Scientific Reports 15:41843. 10.1038/s41598-025-25782-y
Nadasen T, Buitendag C, Visser R, Welgemoed T, Hein I, Berger DK. (2025) A latent invader: transcriptomics reveals Cercospora zeina’s stealth infection strategy of maize and immune-activating effectors. Frontiers in Plant Science 16:1-23. 10.3389/fpls.2025.1703682