Tecoma rust

The fungus's life cycle involves the formation of multiple spore types, which allows it to spread rapidly during the growing season. The mycelium penetrates deep into the plant tissues, disrupting cellular metabolism and blocking photosynthesis.

This pathogen possesses high adaptability, surviving in infected plant debris or fallen leaves. This creates persistent infection reservoirs in gardens where the host plant is grown for multiple years.

The pathogen primarily affects members of the Bignoniaceae family, particularly plants of the genus Tecoma. Its narrow specialization allows it to efficiently exhaust the resources of its specific host.

Microscopic structures of Prospodium tuberculatum spores feature characteristic tubercles (bumps), which help the spores survive adverse environmental conditions and persist in the field.

Initial symptoms of the infection include small chlorotic spots on the upper side of the leaf, which eventually develop into dark brown or necrotic lesions.

On the undersides of the leaves, pustules—the spore-producing structures—are clearly visible. These appear as powdery masses, often surrounded by a yellowish halo of damaged tissue.

In areas of severe infection, leaf tissue dies, leading to premature yellowing and heavy leaf drop. This significantly impacts the plant's aesthetic appeal and overall health.

When stems and petioles are infected, deformation and curling of the young shoots often occur. In advanced cases, the fungal mycelium colonizes large areas of the plant, causing dieback.

• Yellowing and premature leaf drop
• Brown pustules on the leaf undersides
• Curling and deformation of shoots
• Stunted growth and lack of flowering
• Necrosis on stems and petioles

The development of Tecoma rust is directly dependent on air humidity levels. High humidity (above 70%) and the presence of moisture on the leaf surface are critical for spore germination.

The optimal temperature range for the pathogen's development is between +18 and +25 degrees Celsius. In these conditions, the incubation period is significantly shortened, accelerating the spread of the infection.

Dense plantings that impede air circulation contribute to moisture buildup within the canopy. This creates an ideal microenvironment for the rapid transmission of the fungus between adjacent plants.

Insufficient lighting and low sun exposure weaken the plant's natural defense mechanisms, making it more susceptible to the penetration of fungal hyphae into the leaf tissues.

Spore dissemination occurs via air currents, rain splashes, overhead irrigation, or through contaminated pruning tools used on infected specimens.

The primary damage results from the loss of photosynthetic leaf surface. Due to extensive leaf drop, the plant cannot accumulate sufficient energy reserves for the winter dormancy period.

Chronic stress caused by severe rust infection leads to poor flowering; flower quality declines sharply, or the plant may fail to bloom entirely.

Weakened by the fungus, plants become vulnerable to secondary pests and other opportunistic pathogens. Root system stress is also often observed, which may lead to plant mortality during winter.

In nursery settings, this disease can cause serious economic losses, as infected stock loses its commercial value and cannot be sold.

Prolonged parasitism of the fungus on perennial cultures leads to the gradual drying out of individual branches and eventually the entire aerial part of the plant.

The main prevention method involves strict adherence to horticultural practices: timely pruning to improve canopy aeration and avoiding overhead irrigation.

In autumn, it is essential to collect and destroy all plant debris, as the fungal spores can overwinter in fallen leaves.

For treatment, systemic and contact fungicides are used. Copper-based products or specific rust-targeted systemic fungicides typically yield the best results.

Applications should be performed regularly upon the first sign of symptoms, repeating every 10–14 days depending on weather conditions and disease severity.

When purchasing new nursery stock, conduct a thorough inspection, as latent forms of the infection can easily be introduced into your garden along with new plants.