Lettuce is one of the most widespread crops in the world. However, it requires certain growing conditions that can cause situations that can generate pests and diseases that can kill crops. There are different types of lettuce diseases recognizable to the naked eye to be treated quickly to avoid major disasters.
For this reason, we are going to dedicate this article to tell you what the main lettuce diseases are, how to recognize them and what are their treatments.
Contents
lettuce diseases
white rot
This disease is one of the most common in lettuce. We are going to see what its characteristics are, what damage it produces and how to deal with it.
It can occur in any vegetative state of lettuce, even during transplanting. Its development is always influenced by climatic and cultural factors: excessive humidity, sudden changes in temperature, soil that is too cold at the time of planting, insufficient ventilation and injury or necrosis of plant tissue.
The main sources of disease transmission are conidia and plant debris, which are dispersed by wind, rain splash, plastic and condensation droplets in irrigation water. Conditions favorable for disease development are temperature, relative humidity and crop phenology.
The optimum relative humidity range is around 95% and the temperature varies between 17ºC and 23ºC.
Here is the damage caused by this disease:
- It can affect small plants at the seedling stage, causing immediate death or preventing their emergence.
- In young plants, the attack generally begins at the base of the leaves, and once attacked, the leaves fall to the ground, favoring the development of parasites that kill the plant after a few days.
- In mature plants, foci begin in tissues that are necrotic or weakened due to imbalances, physiological damage, or bacterial attack. From there, if the environmental conditions are favorable, it invades new tissues.
- Sometimes the primary infection comes from the soil with Botrytis sclerotiorum accompanied by Sclerotium. In this case, the first attack occurs in the area around the neck of the plant, causing the outer leaves to fall to the ground in such a way as to favor the development of the disease.
- Post-harvest losses too are important and occur in lettuce stored with latent infection. In incubation conditions with high relative humidity, healthy lettuce in contact with it may become contaminated.
- The first stage of Sclerotinia infection develops in tissues near the soil, so it is located in the area where the attack on the crown of the plant begins. These can occur both in young and adult plants, although their incidence is greater from the heart due to the special humid microclimate that develops in the soil.
- Affected plants stop growing, turn yellow and dry out. They offer no resistance when it comes to remove them, as they will wet, soften and rot the whole neck and the area of the base of the outer leaves.
To prevent and act against white rot, we can do the following:
- Wider planting frames during high risk periods.
- Transplant to a ridge to improve ventilation.
- Seed varieties resistant to different varieties of Bremia lactucae are used.
- The preventive treatment starts from the seedbed until the end of the cycle, in plots prone to diseases.
Other Lettuce Diseases
alternate
When identifying this fungal disease, it is necessary to look for small black spots on lettuce leaves. As per usual, thrives in high humidity conditions precautions are therefore sometimes taken during the rainy season.
anthracnose
It usually appears on the oldest leaves before the others, and It predominates especially in the central nervous system, petioles and leaves.
Small sunken yellowish spots with red or necrotic edges appear on these leaves. Over time, this reddish ring expands inward, causing necrosis of the entire spot.
powdery mildew
Powdery mildew is a well-known fungal disease that affects almost all crops. It usually grows on the upper and lower sides of the leaves, and the outer leaves are covered in white mycelium and have a powdery appearance.
gray rot
This fungus can appear in any vegetative state of a lettuce crop. It is usually related to high humidity, so irrigation control is very important. Ventilation is also a good technique to prevent the spread of this disease.
The attack usually begins on the lower part of the lettuce, although it can also appear on leaves with physical damage, problems or disease.
septoria
Septoria produces spots on the underside of leaves. For this fungus to appear, crops must be in areas with high humidity or rainy season. Small irregularly shaped chlorotic spots appear on the leaves. Over time, these spots become necrotic and form chlorotic rings around them, a symptom of disease progression.
sclerotin
The disease causes a soft-looking white rot on lettuce leaves. The infection starts at the base of the plant and spreads over time. This fungus can remain in the soil for up to 5 years, so hygiene techniques such as exposure to sunlight are recommended. It usually thrives in conditions of high humidity, temperatures between 25-28ºC, sun and raintherefore spring is generally more abundant.
Black circular spots with concentric circles appear on the leaves. These necrotic spots first appear on the lower leaves of the plant and spread from there. This can lead to defoliation and premature death.
To prevent it, early ripening and excessive leaf moisture should be avoided. Acaricides, Mancozeb or Zineb can be used. Applications They must be repeated every 10 or 15 days in order to completely eliminate this disease.
Hopefully with this information you can learn more about lettuce diseases and their characteristics.