Damage

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

Nicole M. Van Dam, Mesfin Wondafrash, Vartika Mathur , Tom O. Tytgat. (2018) Differences in Hormonal Signaling Triggered by Two Root-feeding Nematode Species Result in Contrasting Effects on Aphid Population Growth. Frontiers in Ecology and Evolution 10.3389/fevo.2018.00088
Mlonyeni XO, Wingfield MJ, Greeff JM, Wingfield BD, Slippers B. (2018) Genetic diversity of Amylostereum areolatum, the fungal symbiont of the invasive woodwasp Sirex noctilio in South Africa. Forest Pathology :e12449. 10.1111/efp.12449
Tan YP, Shivas RG, Marney TS , Edwards J , Dearnaley J , Jami F , Burgess TI. (2018) Australian cultures of Botryosphaeriaceae held in Queensland and Victoria plant pathology herbaria revisited. Australasian Plant Pathology PDF
Jami F , Marincowitz S, Crous PW, Jacobsohn A, Wingfield MJ. (2018) A new Cytospora species pathogenic on Carpobrotus edulis in its native habitat. FUSE 2 10.3114/fuse.2018.02.03 PDF
Ali DB, Marincowitz S, Wingfield MJ, Roux J, Crous PW, McTaggart AR. (2018) Novel Cryphonectriaceae from La Réunion and South Africa, and their pathogenicity on Eucalyptus. Mycological Progress 10.1007/s11557-018-1408-3