Parsley (botanical name Petroselinum crispum) is a flowering plant typically cultivated in Europe and the Mediterranean region. It belongs to the Apiaceae family and is biennial.
The plant has tiny green leaves and soft stems and is usually used as a garnish in European and American cuisines.
Apart from having countless health benefits, Parsley also serves as a beautiful addition to gardens.
Parsley is a sensitive plant, and improper plant care can easily result in the formation of white spots over time.
Why Does My Parsley Have White Spots?
There are several reasons why your Parsley has developed white spots. These include fungal infections like powdery mildew and downy mildew (which cause powdery white spots to aggregate on leaves), viral infections like celery mosaic, and bacterial infections. Other reasons range from pest attacks and insufficient sunlight to weevil eggs on Parsley leaves.
Seven Causes of White Spots on Parsley
1. Powdery Mildew
Powdery mildew is an infection caused by several fungal species. In Parsley, powdery mildew caused by Oidium subgenera Pseudoidium results in white powdery spots on the leaves.
Initial symptoms include chlorosis and the development of pustules on the underside of leaves.
These lesions give rise to powdery white spots that gradually spread across the whole plant.
Powdery mildew has higher occurrences during hot summers. The lack of moisture and high levels of humidity encourage the formation of spores. Parsley plants overcrowded in one place, rid the roots of sufficient breathing space.
Roots lacking aeration are vulnerable to pathogen attack.
2. Downy Fungus Mildew
Downy Fungus Mildew is another fungal infection caused by fungi, which are obligate parasites. They belong to the phylum Oomycota.
The disease is also common in Parsley plants and is caused by the fungal pathogen, Plasmopara petroselini.
This plant disease primarily occurs in cool, humid regions. Soggy, wet leaves are more vulnerable to pathogen attack.
As the infection spreads, small yellow spots appear at the adaxial surfaces of the leaves. Moist winds help to disperse the microscopic spores.
At the underside of Parsley leaves, hyphae’s rapid growth gives way to white mycelium that slowly engulfs the whole plant.
Leaves begin to wither, and necrosis results in the death of different parts of the plant.
3. Celery Mosaic Virus
Another cause of white spots on Parsley is the celery mosaic virus. The virus gets its name from the mosaic of white circles it produces on parsley leaves.
The celery mosaic infection can be identified by stunted growth of plants and spots that initially appear as faint yellow and slowly transition into a pale white color.
The virus is transmitted through aphids, which act as vectors. When aphids infected with the virus feed on Parsley plants, the pathogen is carried to the plant system.
Over time, the symptoms develop, and the infection severely affects the plant’s growth and development.
4. Pest Attack
When pests such as aphids, thrips, and whitefly attack the parsley plants, white spots slowly begin to appear on the leaves. These spots can either be an indication of feeding injury or can be the eggs of the pests.
If your plant has dusty leaves, then it may be vulnerable to the attack of mites. Moreover, over-fertilized plants have buds that attract several insects towards the plant.
One more cause of numerous white spots on Parsley leaves is the eggs of insects such as the Carrot Weevil.
While the insect hibernates beneath the soil in cold seasons, it is reasonably active during the hot seasons. They reproduce through tiny eggs that appear as white spots to the naked eye.
You can expect to see these spots in June and July when carrot weevil is in its reproductive stage. The eggs initially appear as white and blacken when they are ready to hatch.
5. Bacterial Infection
Cold, humid places encourage the growth of bacteria that cause bacterial leaf spots. These are tiny microscopic organisms that divide rapidly by binary fission at 75-85 degrees Fahrenheit (23-29 degrees Celsius).
If the infection spreads across the entire plant, growth is inhibited.
During the early stages of infection, yellow and black spots aggregate across the mid-rib of the parsley leaves. In older leaves, these spots whiten, and the leaves shrivel up and die.
6. Hard Water and Saline Soil
Hard water is plain water containing high concentrations of dissolved minerals. These minerals include calcium bicarbonate, magnesium sulfates, magnesium carbonates, and sodium chloride.
When water travels through limestone or gypsum deposits deep within the soil, the carbonates dissolve in it.
When gardeners use hard water to water their Parsley plants, they may observe white chalky deposits on the leaves. The same can be observed with the excessive use of fertilizers.
This is because while the water evaporates, the high salt content remains on the leaves in the form of white deposits.
Another reason can be that as Parsley plants have halophytic ancestors, they extrude extra salt on the leaf surface, to stabilize pH levels within the plant.
It usually happens when Parsley is grown in saline soil, and the plant needs to get rid of the excessive salt.
You can quickly eliminate these white spots by wiping the leaves or replacing the soil mix with a less saline one.
7. Insufficient Sunlight
Lack of sufficient sunlight inhibits the plant from producing enough chlorophyll. Since chlorophyll is responsible for leaves’ green color, its deficiency results in white patches on the leaves.
To avoid this situation, you can ensure that your plant has enough sunlight exposure.
Five Solutions to White Spots on Parsley Leaves
1. Use of Fungicides
In the previous section, we mentioned fungal infections several times. Fungi constitute the most prominent pathogens that attack Parsley, and hence being aware of treatments against these fungal infections is essential.
In the case of powdery mildew, you should spray your plant with Bordo Mix, commonly available in shops. The fungicide is effective against the fungal pathogen, and if the plant is not wholly infected, it can be saved.
You are required to spray once every week till the white spots disappear, and the plant shows promising signs of recovery.
If your Parsley plant has been infected with downy fungus mildew, try using fungicides containing copper hydroxide. At the same time, do not allow the leaves to remain wet for long periods.
Bacterial infections like bacterial leaf spotting also require treatment with fungicides, mainly having high copper concentrations.
However, before you treat your infected Parsley plants with these fungicides, you must consult a plant specialist. After carefully considering the symptoms, he/she would be able to suggest an appropriate fungicide for the respective condition.
2. Use of Insecticides
If you observe white egg-like structures on the leaves of your Parsley plant, chances are they are weevil eggs.
You can get rid of these eggs by spraying your plant with insecticides, like Azinphos-methyl. Azinphos-methyl is rich in organophosphates and is highly effective if consistently used for thirty days.
3. Soil Drainage and Appropriate Irrigation Methods
Overwatering is one of the common causes of viral and fungal attacks. To avoid wet leaves and soggy soil, adopt better irrigation methods like furrow or drip irrigation.
In this way, your soil will receive sufficient water, and leaves will remain moderately dry.
Soil drainage helps reduce humidity levels. To make your soil well-drained, you can stuff the soil with organic matter like compost and natural manure.
4. Maintain Proper Sanitation, Aeration and Plant Hygiene
To prevent future pest attacks, maintaining proper sanitation is crucial. Wipe the leaves of dust and grit, and deeply plow the soil to dig out any insects.
It is equally crucial to make certain that the roots are adequately aerated and have enough breathing space to grow and spread.
5. Dispose of the Plant
Any Parsley plant that has been severely affected by pest attack is beyond treatment. The only course of action is to dispose of the entire plant.
After uprooting the plant, if mites or other insects persist in the soil and adjoining areas, you can use fire as a means to kill all the pathogens.
Before re-planting a new crop in the same soil, ensure that the entire soil mix is replaced, all pathogens are removed, and the area is adequately cleaned.
Frequently asked questions related to white spots on parsley
Can you eat Parsley with white spots?
If the white spots on parsley leaves are due to growth in saline soil, or lack of chlorophyll, then the leaves are safe to eat. However, if bacteria, fungi, or viruses have infected the leaves, it is strictly advised to avoid consuming them.
Does vinegar kill powdery mildew?
Vinegar is chemically acetic acid and is hence effective against fungi. It is recommended to use a dilute solution of vinegar to treat a mild form of the fungal infection. Higher concentrations of vinegar can burn the leaves and should thus be avoided.
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Daniel has been a plant enthusiast for over 20 years. He owns hundreds of houseplants and prepares for the chili growing seasons yearly with great anticipation. His favorite plants are plant species in the Araceae family, such as Monstera, Philodendron, and Anthurium. He also loves gardening and is growing hot peppers, tomatoes, and many more vegetables.