October Pest of the Month: Botryosphaeriaceae fungi

Fungi from the family Botryosphaeriaceae (pronounced bot-tree-oh-sphere-ee-a-see) are common endophytes and dieback pathogens in a wide range of woody shrubs and trees. Endophytes are fungi that live within plants and are either benign or beneficial.

Fungi from this family can be present as endophytes within a plant for a long period of time without causing any detrimental effects, sometimes many years.

Many species of Botryosphaeriaceae fungi, however, can become aggressive pathogens causing cankers and dieback of growing tips and stems. Once present in the main stem of a plant individuals will usually die, though this can sometimes take many months in the case of large trees.

These pathogens are important for the production nursery industry because they can unknowingly be spread in infected plants that appear healthy at the time of sale/planting. This is particularly important for forestry seedlings, ornamental and landscape trees and grafted fruit and nut seedlings. Proactive management is required to prevent endophytes from becoming pathogenic and causing disease. This involves preventing wounds and protecting pruning and graft wounds with an appropriate fungicide. Remove dying and dead twigs promptly as early infection can be successfully eradicated and reduces the inoculum load in the crop. Provide optimal growing conditions as plant stress can increase risk of an endophyte from becoming a pathogen, particularly water stress and mechanical damage (e.g. from insects).

For more information on Botryosphaeriaceae fungi refer to the nursery paper on endophytes and latent pathogens. In addition, images of symptoms caused by a range of genera including Botryosphaeria, Neofusicoccum, Diaporthe and Lasiodiplodia are available at the Pest ID tool (search for these genera to find the images).

Imagery: Stem dieback and vascular discolouration caused by Botryosphaeria sp. on Leucospermum. Note many black fruiting bodies present on stem that would collectively contain millions of spores.