Ambrosia Beetles

An ambrosia beetle, commonly known as Polyphagous Shot Hole Borer (PSHB) Euwallacea fornicatus (Coleoptera: Curculionidae: Scolytinae), is considered to be a pest, due to its ability to damage trees by acting as a vector for a pathogenic fungi. Fusarium euwallaceae, the fungal symbiont of the PSHB, is inoculated into the tree by the beetle. Eventually, the fungal symbiont prevents the transport of water and nutrients by invading the xylem, that leads to Fusarium dieback and the eventual death of the host tree. This pest-pathogen complex has emerged as an invasive pest in Israel and the United States of America (California), causing severe damage and significant economic losses to agricultural, ornamental and urban trees, especially to their avocado industries.

This pest-pathogen complex was detected in South Africa damaging Platanus x acerifolia (London Plane) trees in the National Botanical Gardens, KwaZulu-Natal. Recently, it was detected on a backyard tree and in a commercial avocado orchard. Control management strategies for this pest complex are limited due to inefficient trapping mechanisms, lack of biocontrol measures and inefficient fungicides. The use of resistant/tolerant trees could serve as a potential control strategy. Current research within the Avocado Research Programme (ARP) is therefore aimed at identifying Fusarium spp. isolates sampled from avocado trees to determine the extent of the threat to industry, after which the taxonomy of these isolates will be defined.  We are also in the process of determining the threat on various, commonly growth avocado cultivars through the use of multiple pathogenicity trials.

 

*Read more about Ambrosia beetles and Fusarium dieback on our Fact sheet here.

 

ARP Team Members

 

Images from left to right: 1. Xylosandrus crassiusculus fungal symbiont Ambrosiella roeperi in culture. 2. Internal symptoms of PSHB infestation as beetles establish a network of galleries. 3. PSHB interception traps used in orchards.

 

New Publications

Hlongwane NL, Dzomba EF, Hadebe K, van der Nest MA, Pierneef R, Muchadeyi FC. (2024) Identification of signatures of positive selection that have shaped the genomic landscape of South African pig populations. Animals 14:235. 10.3390/ani14020236
De Vos L, van der Nest MA, Santana QC, van Wyk S, Leeuwendaal KS, Wingfield BD, Steenkamp ET. (2024) Chromosome-level assemblies for the pine pitch canker pathogen Fusarium circinatum. Pathogens 13(1):70. 10.3390/pathogens13010070
Joubert M, van den Berg N, Theron J, Swart V. (2024) Global transcriptomic analysis in avocado nursery trees reveals differential gene expression during asymptomatic infection by avocado sunblotch viroid (ASBVd). Virus Research 339:199263. 10.1016/j.virusres.2023.199263. PDF
Anbu SP, Swart V, van den Berg N. (2023) Unmasking the invaders: NLR-mal function in plant defense. Frontiers in Plant Science 14:1307294. 10.3389/fpls.2023.1307294 PDF
Backer R, Naidoo S, van den Berg N. (2023) The expression of the NPR1-dependent defense response pathway genes in Persea americana (Mill.) following infection with Phytophthora cinnamomi. BMC Plant Biology 23(1):548. 10.1186/s12870-023-04541-z PDF
Kooverjee BB, Soma P, van der Nest MA, Scholtz MM, Neser FWC. (2023) Copy Number Variation Discovery in South African Nguni-Sired and Bonsmara-Sired Crossbred Cattle. Animals 13(15):2513. 10.3390/ani13152513
Dzomba EF, Van der Nest MA, Mthembu JNT, Soma P, Snyman MA, Chimonyo M, Muchadeyi FC. (2023) Selection signature analysis and genome-wide divergence of South African Merino breeds from their founders. Frontiers in Genetics 13:932272. 10.3389/fgene.2022.932272
Wingfield BD, Berger DK, Coetzee MPA, Duong TA, Martin A, Pham NQ, Van den Berg N, Wilken PM, Arun-Chinnappa KS, Barnes I, Buthelezi S, Dahanayaka BA, Durán A, Engelbrecht J, Feurtey A, Fourie A, Fourie G, Hartley J, Kabwe ENK, Maphosa M, Narh Mensah DL, Nsibo DL, Potgieter L, Poudel B, Stukenbrock EH, Thomas C, Vaghefi N, Welgemoed T, Wingfield MJ. (2022) IMA genome‑F17 Draft genome sequences of an Armillaria species from Zimbabwe, Ceratocystis colombiana, Elsinoë necatrix, Rosellinia necatrix, two genomes of Sclerotinia minor, short‑read genome assemblies and annotations of four Pyrenophora teres isolates from barley grass, and a long-read genome assembly of Cercospora zeina. 13:19. 10.1186/s43008-022-00104-3
Swalarsk Parry BS, Steenkamp ET, Van Wyk S, Santana QC, van der Nest MA, Hammerbacher A, Wingfield BD, De Vos L. (2022) Identification and characterization of a QTL for growth of Fusarium circinatum on pine-based medium. Journal of Fungi 8(11):1214. 10.3390/jof8111214
Wienk R, Mostert‑O’Neill M, Abeysekara N, Manosalva P, Freeman B, van den Berg N. (2022) Genetic diversity, population structure and clonal verification in South African avocado cultivars using single nucleotide polymorphism (SNP) markers. Tree Genetics and Genomes 18(41) 10.1007/s11295-022-01573-8 PDF