Downy mildew on lemon leaves

Disease name: Downy mildew on lemon leaves

The scientific name: Oidium citri

Type of disease: fungal

Disease family: Oomycete

(White to gray fuzzy bumps on lemon leaves)

• The causes of disease:

This disease is caused by a fungus Oidium citri Which usually spreads in the spring, white to gray fuzzy bumps form on the leaves of the affected plant, which is why the disease is given this name.

• Symptoms of the disease:

Young leaves turn white or gray as a result of the presence of burrs, and in the case of severe infection, they cause deformation of the leaves and buds, leading to the premature fall of leaves and fruits and the death of twigs and branches.

• Disease development cycle:

The disease can be transmitted over long distances by wind, and agricultural equipment such as pruning tools, mechanical harvesters, etc. have a role in transmitting the disease from one plant to another.

• Conditions suitable for the spread of the disease:

The fungus spreads in shady, poorly ventilated orchards, and it needs moderate to cool temperatures. This is the reason for its spread in the spring, when rainfall is frequent and temperatures remain cool.

• Losses resulting from the spread of the disease:

If the infestation is neglected, the infestation may develop and may cause other diseases, which greatly reduces tree productivity and fruit quality. Therefore, continuous monitoring of the field and early detection are among the most important factors to avoid major losses in the field.

(Parts of the lemon tree are infected with downy mildew)

• Control:

1. Remove infected leaves and burn them away from the field.
2. Cleaning the field of harmful plants and plant residues.
3. Use of pesticides containing dithiocarbamate.
4. Avoid overhead watering and watering in the early morning hours to prevent providing a damp environment to suppress the spread of the disease.

• preventive measures:

1. Planting disease-resistant varieties.
2. Determine good distances between trees planted in the field in order to give them proper ventilation and avoid transmitting infection between close trees.
3. Organizing and sterilizing agricultural tools before use.
4. Good and moderate fertilization.

• Sources:
• https://www.lovethegarden.com/uk-en/article/downy-mildew
• https://www.daf.qld.gov.au/__data/assets/pdf_file/0006/65166/Citrus-Citrus-powdery-mildew.pdf
• https://www.gardeningknowhow.com/plant-problems/disease/downy-mildew.htm