Fundamentals of Plant Diseases - Slide 25 - BACTERIA: SYMPTOMS: BLIGHT

Summary

The video script discusses bacterial blight of geraniums, a common disease affecting plants when grown and saved year after year. It starts as angular spots with yellow halos, progressing to wedge-shaped infected areas. The bacteria move towards the petiole, causing leaf collapse. Overwintering geraniums can harbor the bacterium asymptomatically, leading to disease when populations increase. Management involves discarding infected plants and decontaminating with bleach or alcohol to prevent spread.

Takeaways

• 🌿 Leaf blights are diseases that can affect plants, including geraniums, and are caused by bacterial pathogens.
• 🔍 Bacterial blight of geranium starts as individual spots and can be identified by angular, yellow-haloed lesions on leaves.
• 📈 The infection progresses, causing wedge-shaped areas to turn into a pie-shaped pattern as the bacteria move towards the petiole.
• 🍂 Ultimately, the bacteria reach the main stem, leading to the collapse of the petiole and the entire leaf, hence the term 'blight'.
• 🌡 The disease is more likely to occur in geraniums that are saved and overwintered, as the bacterial population can increase over time.
• 🌱 Often, geraniums can harbor the bacterium without showing symptoms, which can lead to disease when the population grows large enough.
• 🗑️ The best management practice for bacterial blight is to discard infected plants to prevent the spread of the bacterium to healthy plants.
• 🧼 Decontamination is crucial after discarding infected plants; use a 10% bleach solution or 70% alcohol to clean pots and surfaces.
• 🏠 It's important to decontaminate any objects or surfaces that may have been in contact with infected plants to stop the disease from spreading.
• ⚠️ Overwintering plants can increase the risk of bacterial blight, so it's essential to monitor plants for signs of disease and act promptly.

Q & A

What is bacterial blight of geranium?

Bacterial blight of geranium is a common disease that affects geranium plants, causing leaf spots and eventually leading to the collapse of the petiole and the entire leaf.

How does the disease typically start?

The disease starts as individual spots on the leaves, which can be angular and have yellow halos around them.

What is the progression of bacterial blight on geranium leaves?

The infected area becomes larger and takes on a wedge-shape, moving from the edge of the leaf towards the petiole, resulting in a pie-shaped infected dead area.

What happens when the bacterium reaches the main stem of the geranium?

When the bacterium reaches the main stem, it causes the petiole to collapse, leading to the entire leaf collapsing, which is why it is referred to as a blight.

Why is it common to encounter bacterial blight when growing geraniums?

It is common to encounter bacterial blight when growing geraniums, especially if you save and overwinter your plants, as the bacterium can harbor in the plants without showing symptoms until the population increases.

What is the best management strategy for bacterial blight of geranium?

The best management strategy is to discard infected plants, as there is no way to clean or cure them once they have the bacterial disease.

Why is it important to discard infected geranium plants?

Infected plants should be discarded to prevent the bacterium from spreading to healthy plants, which could lead to additional disease.

What steps should be taken after discarding infected geranium plants?

After discarding infected plants, it is necessary to decontaminate pots, surfaces, and any objects that may have come into contact with the infected plants.

What solutions can be used for decontamination after handling infected geranium plants?

A 10% bleach solution or 70% alcohol can be used to decontaminate pots and surfaces that may have been contaminated by the infected plants.

Can geraniums harbor the bacterium without showing symptoms?

Yes, geraniums can harbor the bacterium without showing symptoms, and it is only over time that the bacterial population increases to a point where infection and disease occur.

How does the bacterial blight spread within a geranium plant?

The bacterial blight spreads within a geranium plant from the edge of the leaf back towards the petiole, causing the infected area to enlarge and eventually collapse the leaf.