Cucumber Leaf Spot Treatment For Angular Leaf Spot On Cucumbers
Angular leaf spot (ALS) is one of the most common vegetable disease in cucurbit family. ALS is caused by several different species of fungus. The main cause of ALS are various soilborne fungi, such as Rhizoctonia solani, Phytophthora infestans, Pythium spp., Fusarium oxysporum and others.
These soilborne fungal pathogens attack the vascular tissues of plants causing wilting, stunted growth and death.
The problem with these soilborne fungi is that they multiply rapidly, which results in rapid spread of the disease from one part of the field to another. This means that if a single infected plant becomes infected it could potentially affect many other nearby plants within its range. This makes prevention of the disease difficult because there is no way to control or eradicate all the affected plants.
Another problem with these soilborne fungi is that they do not die when exposed to sunlight. They remain viable even after being left out in the sun for long periods of time. Thus, once a plant becomes infected, it may continue spreading to other nearby plants without any intervention from humans.
The best way to prevent the disease from spreading is to prevent the pathogen from getting inside your crop. In some situations, if the crop has a high tolerance to the pathogen, it may be possible to use biological control to manage the infection by applying beneficial microbes such as sulfur-based bacteria, which are naturally occurring in the soil and cannot infect plants.
It is important to have a clean garden and use clean seedlings. This can help prevent the disease from spreading from one part of the garden to another. Also, proper sanitation is important because it prevents the spread of the pathogen from one part of the garden to another after the plants become infected.
It is also important to plant your crop in a manner that allows for good air circulation so that plants are less likely to become infected. For some crops it may be helpful to plant your crops in hills rather than in rows. This allows air to move through the plant canopy better and prevents water from stagnating on the leaf surface.
One of the reasons that angular leaf spot is so difficult to control is that there are several different species of fungus that can cause angular leaf spot. Even if you manage to kill off the initial fungal pathogens that infect your crop, others may become active later in the growing season when the weather is more favorable for their growth as well as the growth of your crop.
There are several different types of chemicals and bio-controls that can be used to help manage angular leaf spot but none of them are very effective, especially when used alone. The only thing that works to any degree is a combination of several different strategies.
One of the main ways of managing angular leaf spot is through the use of crop rotation. Rotating your crops to a part of your garden that hasn’t had a susceptible crop for at least three years helps reduce the amount of soil-borne pathogens that may be in the soil. This doesn’t completely eliminate the problem but it does help a little.
Another thing you can do, if the disease hasn’t become too severe, is to remove all the leaves from the plant and dispose of them (preferably in the garbage). This prevents the spread of the disease from one part of the plant to another.
A more drastic approach is to sterilize your tools by dipping them in a 5% sodium hypochlorite (the common household bleach) for at least one minute or by burning them. Tools that are used on infected plants should not be used on healthy plants.
In extreme cases, such as an outbreak or highly susceptible crop, fungicide might be needed to help control the disease. Fungicides can be expensive and often are only effective when used at the first sign of the disease. Even then, the cost of the fungicide might exceed the value of the crop that you are trying to protect.
It is best to try some of the less-toxic methods first before resorting to fungicides.
Here are some organic ways to manage angular leaf spot:
Rotate your crops; make sure that you don’t plant susceptible plants in the infected bed for at least three years.
Remove leaves from plants (and dispose of them) as soon as you notice the disease. This will help slow the spread of the disease.
Plow in organic matter (cover crops, manure, etc.) in beds that have had a susceptible crop to help build up the organic matter in the soil. This will make the soil more damp and promote the growth of the natural enemies of the pathogens.
Remove weeds (especially those known to harbor the disease) from the beds.
Fill holes made by plant roots with soil that has had organic matter mixed into it. This helps prevent the movement of the soil-borne pathogens within the soil.
Avoid working in your beds when the soil is wet as this encourages the movement of the pathogen.
Fungicides can be used to prevent or reduce disease problems. Fungicides can be effective but must be used before or at the first sight of disease.
Fumigate your soil with the use of a gas spary (such as CH3CCl3) in the spring. The use of this gas greatly reduces the population of certain fungal pathogens that might infect your plants.
Spray your plants with copper based fungicides. These are fairly effective but must be reapplied every seven to ten days.
Use organic fungicides containing oils, Vinegar or H202 (Hydrogen Peroxide). These organic fungicides are not as effective as the chemical ones but they are still somewhat useful.
Bacteria: (Bacterial Spot)
This disease is caused by the Xanthomonas campestris pv. musacearum bacteria. It is most common in areas with high humidity and cool temperatures.
The symptoms of this disease are the appearance of dark spots on the leaves. The spots start out dark-green or purple in color and then turn brown as they mature.
These spots can eventually cover the entire leaf, turning it completely brown and necrotic (die). This disease does not affect the rest of the plant, just the leaves. This may cause defoliation but it does not cause death.
The rest of the plant is usually able to produce more leaves to replace those that have been lost.
This disease is most common in seedlings and younger plants. Once a plant is over a month or two old it has a greater resistance to the bacteria. This is why it is so common in seedlings.
The seeds can be infected with the bacteria when they are planted.
The signs of this disease are the dark brown spots on the leaves (usually starting on the older leaves first), leaf drop and slow growth. There is not much you can do to prevent this disease. It is a common problem in areas where the rain makes the air humid, such as in the Pacific North West.