Lupin phomopsis

The fungus overwinters in soil and on crop debris, surviving as pycnidia and mycelium. It can persist in the soil for several years, making it a challenging pathogen to eradicate through crop rotation alone.

Dissemination occurs via conidia that are released from pycnidia during rainfall. These spores are dispersed by splashing water and wind, facilitating the spread of the disease to healthy plants within the field.

As a specialized parasite, Plenodomus lupini primarily targets various species of lupin. It is recognized as one of the most significant fungal threats to lupin cultivation worldwide.

The fungus penetrates the plant through natural openings or mechanical wounds, subsequently colonizing the stems and disrupting the transport of nutrients within the plant host.

The disease is characterized by the appearance of brown or dark-colored circular spots on leaves, petioles, and stems. These lesions expand over time, often coalescing to cover significant portions of the plant tissue.

Visible black dots, representing the fungal pycnidia, appear in the center of the lesions. This specific sign is a key diagnostic feature for confirming the presence of the pathogen in the field.

Stems affected by phomopsis become brittle and prone to breakage, which is a major symptom that impacts crop lodging and harvest efficiency. Plants with severe stem infections often exhibit early senescence.

Young seedlings infected by the fungus may undergo damping-off, leading to reduced stand density. On mature plants, the disease progress often results in premature leaf drop and stunted growth.

Infected pods show mottled symptoms and can become shriveled, resulting in low-quality seed. These seeds often serve as a carrier for the pathogen, spreading it to subsequent planting seasons.

Phomopsis development is highly dependent on environmental conditions, particularly moisture. Temperatures ranging from +18 to +25 degrees Celsius are optimal for fungal growth and sporulation.

Extended periods of high relative humidity, frequent rain showers, and foggy mornings significantly increase the rate of infection. Moist conditions are essential for the release and germination of conidia.

Poor crop rotation practices contribute to the build-up of the pathogen in the field. Growing lupin on the same land too frequently is a primary cause of severe disease outbreaks.

Dense planting patterns that limit air circulation create a conducive microclimate for the fungus. Lack of airflow prevents moisture from evaporating, prolonging the duration of leaf wetness.

Mechanical injuries resulting from pest feeding or agricultural machinery create entry points for the pathogen, accelerating the infection process in vulnerable lupin crops.

Lupin phomopsis causes significant economic loss by reducing both green mass and grain yields. Infected plants suffer from restricted growth, which drastically lowers their photosynthetic capacity.

Stem damage prevents the translocation of water and nutrients to the developing pods, leading to poor pod filling and decreased seed quality, often rendering the yield unsuitable for marketing.

Increased susceptibility to lodging makes harvesting difficult and results in physical loss of crop volume. In severe cases, entire plots may fail due to high disease incidence.

Seeds harvested from infected fields have reduced viability and carry the fungus, which can lead to seedling blight when used for the following season's planting.

The disease also increases operational costs due to the need for preventative fungicide applications and the potential requirement for additional soil treatment measures.

The most effective strategy for managing phomopsis is a strict crop rotation cycle of at least 4 to 5 years, which significantly reduces the pathogen pressure in the soil.

Using certified, fungicide-treated seeds is crucial to ensure that the initial plant population remains free from the pathogen and to reduce early-season infection risks.

• Deep plowing to bury crop residues and prevent the survival of pycnidia.
• Selecting resistant or tolerant lupin varieties suitable for local climatic conditions.
• Ensuring optimal plant spacing to promote airflow and decrease humidity within the canopy.
• Applying targeted foliar fungicides at the onset of symptoms to suppress the fungal spread.

Balanced fertilization with phosphorus and potassium can bolster the plant's natural immunity, helping it resist early colonization by Plenodomus lupini.

Regular field scouting is essential for early detection. Monitoring allows for the identification of disease hot spots, enabling timely and localized control measures to minimize overall impact.