Tree disease and death can arise from a multitude of factors, including living organisms (biotic) such as insects and fungi, or abiotic agents such as frost, drought and chemical damage. In order to adjust management practices appropriately, it is crucial to correctly identify the cause of damage to trees. The following section summarizes some of the most common causes of tree damage or disease and provides guidelines for distinguishing between the different categories of damage, disease and decline.

Distinguishing between causes of tree health problems

Abiotic Biotic
Non-living (eg. chemicals, frost, drought) Living (Fungi, bacteria, insects)
Absence of host specificity Often host specific
Non-infectious Infectious (can spread from one tree to another)
Usually a gradient visible (worst near source of origin, with impact gradually becoming less as distance from source increases)
Damage usually of same age/phase of expression
Often random in the plantation
Damage often at different stages of development as pathogen/pest spread from one tree to another

Signs and Symptoms

Disease and pest problems may be identified by observing certain signs and symptoms of infection / infestation. Signs include the presence of fungal fruiting bodies, or egg capsules of insects, while symptoms include leaf spots, defoliation, cracking of stems, wood stain etc. Characterizing the type of damage and the visible signs is useful in making accurate diagnoses.

New Publications

Clasen FJ, Pierneef RE, Slippers B, Reva O. (2018) EuGI: a novel resource for studying genomic islands to facilitate horizontal gene transfer detection in eukaryotes. BMC Genomics 19:323. 10.1186/s12864-018-4724-8
De Beer ZW, Marincowitz S, Duong TA, Wingfield MJ. (2018) (2592) Proposal to conserve Endoconidiophora fagacearum (Bretziella fagacearum, Ceratocystis fagacearum) against Chalara quercina (Thielaviopsis quercina) (Ascomycota: Sordariomycetes: Microascales). Taxon 67:440-440. 10.12705/672.14
Kanzaki N, Tanaka SE, Ito M, Tanaka K, Slippers B, Tabata M. (2018) Some additional bionomic characters of Deladenus nitobei. Nematology 10.1163/15685411-00003168
Barnes I, Fourie A, Wingfield MJ, Harrington TC, McNew DL, Sugiyama LS, Luiz BC, Heller WP, Keith LM. (2018) New Ceratocystis species associated with rapid death of Metrosideros polymorpha in Hawai`i. Persoonia 40:154–181. 10.3767/persoonia.2018.40.07
Dittrich-Schröder G, Hoareau TB, Hurley BP, Wingfield MJ, Lawson S, Nahrung HF, Slippers B. (2018) Population genetic analyses of complex global insect invasions in managed landscapes: a Leptocybe invasa (Hymenoptera) case study. Biological Invasions 10.1007/s10530-018-1709-0