Are your trees at risk? International Year of Plant Health Part 6

23 July 2020

Here’s a handy list of the tree species which have been known to be infected already.

The list shows current host trees in South Africa on which infestations of the polyphagous shot hole borer have been confirmed. The Latin names of species as well as the common names have been included for reference. The lists are divided by exotic and indigenous species. 

Reproductive host trees

The following are host trees in which both the beetles and the fungus establish, and where the beetle successfully reproduces. In most cases, the reproductive hosts will eventually be killed by the fungus.

Exotic species                                

Acacia melanoxylon   -  Blackwood

Acacia mearnsii    -     Black wattle

Acer buergerianum   -  Trident (Chinese) maple

Acer negundo -  Boxelder

Acer palmatum - Japanese maple

Brachychiton discolor - Pink flame tree

Gleditsia triacanthos  - Honey locust

Liquidambar styraciflua - American sweetgum

Magnolia grandiflora -  Southern magnolia

Persea americana   -  Avocado

Platanus x acerifolia   -  London plane

Quercus palustris  -  Pin oak

Quercus robur - English oak

Ricinus communis - Castor bean

Salix alba - White willow

Indigenous SA species

Combretum kraussii - Forest bushwillow

Erythrina caffra  -  Coast coral tree

Podalyria calyptrata - Water blossom pea

Psoralea pinnata  -  Fountain bush

Salix mucronata  -   Cape willow

Virgilia oroboides subsp Ferruginea - Keurboom

A keurboom    A keurboom  ​

A series of images showing how a keurboom is affected by the polyphagous shot hole borer, right down to its core. 

 

Non-reproductive host trees

The following are host trees that are attacked by the beetle and where the fungus establishes, but where the beetle does not successfully breed.

Exotic species

Bauhinia purpurea - Butterfly orchid tree   

Betula pendula - Silver birch     

Camellia japonica -  Common camellia       

Carya illinoinensis - Pecan nut        

Ceiba pentandra - Kapok 

Cinnamomum camphora - Camphor

Citrus limon - Lemon

Citrus sinensis - Orange

Eriobotrya japonica - Loquat

Erythrina livingstoniana -  Aloe coral tree

Eucalyptus camaldulensis - River red gum 

Ficus carica - Common fig   

Fraxinus excelsior - European ash  

Jacaranda mimosifolia - Jacaranda        

Macadamia sp - Macadamia nut           

Melia azedarach - Syringa

Morus sp - Mulberry         

Platanus occidentalis - American plane          

Platanus racemosa - Californian plane        

Plumeria rubra - Frangipani       

Populus nigra - Lombardy poplar

Prunus nigra -  Black plum     

Prunus persica - Peach  

Psidium guajava - Guava 

Schinus molle - Pepper tree      

Taxodium distichum - Swamp cypress           

Ulmus minor = Ulmus procera - English elm     

Ulmus parvifolia - Chinese elm    

Viburnum sinensis - Viburnum       

Vitis vinifera - Grapevine

          

Indigenous SA species

Bauhinia galpinii - Pride of De Kaap

Buddleja saligna - False olive

Calodendrum capense - Cape chestnut

Calpurnia aurea  -    Geelkeurboom

Combretum erythrophyllum    -  River bushwillow

Cordia caffra - Septee tree

Cussonia spicata  -  Cabbage tree/ Kiepersol

Diospyros dichrophylla -    Star apple

Diospyros lycidioides - Monkey plum

Ekebergia capensis - Cape ash

Erythrina lysistemon -  Common coral tree

Ficus natalensis -  Natal fig

Grewia occidentalis - Cross berry

Gymnosporia buxifolia - Spike thorn

Halleria lucida - Tree fuchsia

Harpephyllum caffrum - Wild plum

Melianthus major - Honey flower/Kruidjie-roer-my-nie

Nuxia floribunda - Forest elder

Olea europea subsp. Africana  Wild olive

Podocarpus falcatus - Outeniqua yellowwood

Podocarpus henkelii - Henkel’s yellowwood

Protea mundii - Forest sugar bush

Prunus Africana - Red stinkwood

Rapanea melanophloeos -Cape beech

Schotia brachypetala - Weeping boerbean/Huilboerboon

Senegalia (Acacia) galpinii - Monkey thorn

Vachellia (Acacia) karroo - Sweet thorn

Vachellia (Acacia) sieberiana var. woodii - Paper bark thorn

Virgilia divaricate -  Keurboom

An example of a cross berry tree affected by the PSHB   An eg of a cross berry tree

A cross berry tree affected by the PSHB; and below, a monkey plum tree affected to its core. 

a monkey plum tree  a monkey plum tree affected

The polyphagous shot hole borer (PSHB) manifests differently on species of trees, but it is marked by the iconic holes it leaves in branches which look like the tree has been shot at with a gun. As the PSHB bores through the tree to create its galleries/tunnels where it lays its larvae to feed off the fungus it carries, the trees start to ooze sap as they slowly die.