Lepteutypa cupressi

Lepteutypa cupressi is an ascomycete fungus belonging to the Amphisphaeriaceae family. It is a highly specialized plant pathogen that primarily affects members of the Cupressaceae family.

The fungus develops its mycelium within the plant tissues, specifically targeting the bark and phloem. It is known as the causal agent of a severe canker disease that leads to the decline of trees.

External identification is challenging until reproductive structures emerge. Small, black, semi-immersed fruiting bodies called pseudothecia develop on the dead bark, containing the spores.

The infection spreads via conidia and ascospores dispersed by wind, rain splashes, and insects. High humidity is a critical factor for the initiation of active spore production.

Because the pathogen can be confused with other types of necroses, accurate diagnosis requires a microscopic analysis of fungal cultures isolated from the affected bark zones.

The primary hosts of this fungus are various cypress species, most notably Cupressus macrocarpa. Junipers, thujas, and other related conifers are also susceptible to this disease.

The disease affects both young nursery seedlings and mature ornamental trees in park landscapes. It poses a significant threat to forest stands, especially in Mediterranean-type climates.

The fungus attacks branches and trunks, disrupting the tree's vascular system. Damage to the phloem prevents nutrient transport, causing the gradual drying out of the entire canopy.

The damage is characterized by a loss of aesthetic value, a weakened immune system, and eventual tree death if the infection is severe. Infected trees serve as an inoculum source for neighboring plants.

Symptoms often appear first in the lower or middle tiers of the canopy, gradually spreading upwards. Under favorable conditions, the fungus can destroy large sections of a plantation in a short time.

The first visual sign is localized yellowing, followed by browning of the foliage on individual branches. Eventually, the color turns to a characteristic reddish-brown, and the foliage drops off.

Darkening and necrosis of the bark are visible in the affected areas of the trunk or branches. Increased resin exudation is often observed at the site of infection as the tree attempts to isolate the pathogen.

Peeling back the bark reveals brown necrosis in the cambium and underlying wood. The boundary between healthy and infected tissue is often marked by a distinct dark line.

In advanced cases, tiny black dots (the pseudothecia) appear on the dead bark. This is the most reliable sign for confirming the diagnosis under field conditions.

The overall state of the canopy deteriorates rapidly, becoming sparse and dull. Branch tips often curl, giving the tree a characteristic "tired" appearance before the organ dies completely.

The primary control measure is the sanitary pruning of affected branches. Tools must be disinfected with alcohol or a fungicide solution after each cut to prevent the spread of spores.

Strict adherence to cultural practices is essential. Avoid overcrowding in plantings, which contributes to high humidity and poor air circulation around the canopy, facilitating spore development.

Timely removal and destruction of all plant debris, including fallen needles and pruned branches, are crucial as they serve as the primary reservoir for the infection.

The use of copper-based fungicides (such as Bordeaux mixture or copper oxychloride) during the growing season helps reduce infection risks. Treatments should be preventive, especially during rainy seasons.

Boosting the immunity of conifers with micronutrient fertilizers and plant growth stimulants is recommended. Healthy, well-nourished plants are significantly more resistant to fungal pathogen invasion.