Septobasidium pilosum

The fungus forms distinctive, felt-like or hairy mats on the bark of host plants. These mats, which can vary in color, serve as a protective cover for the scale insects while the fungus absorbs nutrients from the insects and the plant surface.

The lifecycle of this fungus is strictly dependent on the presence of its insect hosts. Without the colonization of scale insects, the fungus cannot thrive or spread effectively in its characteristic form on the tree.

It is predominantly found in warm and humid regions, where climate conditions favor the growth of fungal mats on the multi-year branches of fruit and ornamental trees.

This pathogen acts as a complex biological parasite. It does not kill the host tree immediately but creates a parasitic complex that weakens the plant's structural and physiological integrity over time.

The primary hosts of Septobasidium pilosum include citrus trees, apple trees, pear trees, and various ornamental shrubs. The damage is largely indirect, caused by the protection the fungus provides to the scale insects.

Because the fungal mat shields the scale insects from predators, parasites, and chemical treatments, the insect populations can grow unchecked, leading to massive sap-sucking damage on the plant.

Direct damage occurs as the fungal mat inhibits normal gas exchange and transpiration through the bark. This can lead to localized bark necrosis and the subsequent drying out of branches.

Trees affected by this pathogen often show signs of general decline, including reduced fruit yield, leaf yellowing, and stunted growth in heavily infested areas.

The aesthetic value of ornamental plants is severely reduced, and for commercial fruit orchards, the presence of the fungus increases management costs and lowers market quality.

The most prominent sign of infection is the presence of felt-like or hairy crusts covering the bark. These crusts can range in color from light grey to reddish-brown.

Upon closer inspection, one can always find a colony of scale insects beneath the fungal cover. The presence of these mats is a reliable indicator that the tree is infested with scale insects.

Affected bark may appear cracked, rough, or abnormally textured compared to the smooth, healthy bark of surrounding branches.

In advanced stages of infection, one may observe the dieback of small twigs and branches, often accompanied by the proliferation of the fungal mat over the dying tissue.

A sickly appearance of the tree, combined with visible mats on the stems and branches, confirms the need for immediate phytosanitary intervention.

Control of Septobasidium pilosum primarily focuses on the management of scale insect populations. Without eliminating the insect host, the fungus will continue to persist and spread.

Application of systemic insecticides is essential to penetrate the protective fungal layers and control the hidden scale insect colonies.

Sanitary pruning is highly recommended; removing and burning severely infested branches is an effective way to lower the inoculum levels in the orchard.

Dormant oil sprays, applied during the tree's winter dormancy, help to mechanically smother the insects and loosen the fungal mats on the bark surface.

• Targeted insecticide treatments for scale insects.
• Sanitary pruning and removal of affected wood.
• Dormant season oil applications for bark cleaning.