A Survey on the Menace of Lingzhi Mushrooms on Trees in Shell Residential Area, Port Harcourt

Abstract

Observations through routine tree surveys and reports by estate managers and residents show an increasing rate of sudden fall of healthy looking trees recently in Shell Petroleum Development Company of Nigeria Residential Area (SPDC RA), thus creating a high potential risk to lives and facility. An earlier survey had suggested that a weakening of the root system due to the presence of mushroom species of a cosmopolitan basidiomycete in the genus Ganoderma may be responsible for the tree falls. Consequently, a team was constituted for an emergency tree hazard hunt exercise using the approved criteria for tree cutting as terms of reference. During the tree hunt exercise, a survey was undertaken with the aim of identifying the mushroom species involved and type of disease, disease symptoms, method of infection/spread, any diagnostic tools for the disease as well as curative and preventive measures for the management of the disease in order to proffer suitable recommendations. Forty-one (41) out of a total of two hundred and seventy-one (271) trees surveyed (15%) were impacted by the mushroom. Disease symptoms include yellowing, necrosis, wilting of the palms fronds and development of a basidiocarp at the tree base. The fungus is soil-borne, spreading from root to root and by migration of airborne basidiospores from basidiocarp. It overwinters in dead woody debris and tree stumps. Some diagnostic tools have been developed both in the laboratory and field for the diagnosis of this disease which include; Calorimetric method using Ethylenediamine-tetraacetic acid, Ganoderma selective media, use of Polyclinal Antibodies (PAbs) and Polymerase Chain Reaction (PCR), Remote Sensing System, application of colour indices using multispectral and thermal camera as well as tomography instrument. The use of trench system, soil mounding, fungicidal treatment and replanting techniques have great potentials in the management of this disease. Periodic checks, routine removal of basidiocarps, geo-referencing and superimposing the impacted trees positions on an existing RA Base map and replanting the cut trees to re-vegetate the environment in phases with seedlings around the camp are recommended. Proper taxonomic study on the Ganoderma species diversity in the RA environment is necessary. Keywords: Shell Petroleum Development Company Residential Area (SPDC RA); Basidiomycete; Basidiocarp; Calorimetric method; Polyclinal Antibodies (PAbs); Polymerase Chain Reaction (PCR); Remote Sensing; Taxonomic study; etc.;