Alternaria rot
Alternaria citri
What is Alternaria rot (Alternaria citri)?
Alternaria rot primarily caused by Alternaria citri, is a fungal disease affecting fruits like navel oranges and lemons. It can occur in citrus-growing areas worldwide, including countries like the United States, Spain, Italy, Brazil, Australia, and others. It is a filamentous fungus found in soil and decaying plant material and can infect crops during growth, harvest, transportation, or storage, leading to postharvest diseases such as Alternaria rot.
How does Alternaria rot (Alternaria citri) occur?
Alternaria citri reproduce through asexual spores called conidia, formed on infected plant tissues or decaying matter. These spores disperse via wind, water, or insects. Under favorable conditions, conidia germinate and infect susceptible plants, causing Alternaria rot. The fungi continue to produce conidia, contributing to disease spread. Environmental factors, host susceptibility, and cultural practices affect their reproductive cycle.
Symptoms
1 - Impact on Plants
Alternaria rot causes damage to affected plants, reducing crop yield and quality. It can lead to fruit or vegetable decay, defoliation, and weakened plant health.
2 - Soil Health
The presence of Alternaria citri in the soil can increase with infected plant debris accumulation. This poses a risk for future crop rotations as the pathogen may infect susceptible plants.
3 - Impact on Environment
The spread of Alternaria rot can have ecological implications. Infected fruits left in fields or improper disposal can serve as a source of inoculum, affecting nearby crops or wild plants.
Solutions
1 - Prevention
1. Maintain good orchard hygiene by removing and destroying infected plant debris and fallen fruits to reduce the inoculum source. 2. Avoid planting susceptible crops in areas where Alternaria rot has been prevalent in previous seasons. 3. Prune plants to improve air circulation and reduce humidity, creating less favorable conditions for fungal growth. 4. Avoid excessive moisture on foliage and fruits, as high humidity promotes disease development. 5. Maintain appropriate temperature and humidity levels during storage to slow down fungal growth and reduce disease progression.
2 - Chemical Control
Examples of fungicides commonly used for managing Alternaria rot include azoxystrobin, captan, chlorothalonil, fludioxonil, mancozeb, pyraclostrobin, and thiophanate-methyl. Consult with local agricultural authorities for specific fungicide recommendations and guidelines.
