Anthracnose: Preventing Leaf Spots and Blights On Your Plants

Ed Wike
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Anthracnose Overview

This is a fungus that’s visible right around the time the leaves first start to appear on your favorite ornamental plants. It’s going to be a burgundy or dark-colored splotches on the leaves. At the beginning stages it’s going to be larger lesions, almost like a paint splotch. And eventually, it will kind of span out to all the leaves.

Appearance

The first appearance that you’re going to see this on your plants is going to be on the soon-to-be-exposed leaves. It’s going to be a very dark, oval-shaped splotching, almost looking like a paint splotch. It’s going to be all over the leaf. Later on, it’s also going to spread out to the older leaves too. It’s going to turn everything a dark burgundy color.

What Is Anthracnose?

It’s a fungus that can plague a wide variety of plants. While some spots are just cosmetic, anthracnose can be deadly to your plants. You may find it affecting the leaves or the fruit or both. In some cases, the lower foliage is affected and the top foliage is fine. This can be a common symptom of both apple stunt and anthracnose.

The fungus grows in humid, rainy conditions and overfertilizing your plants can increase the likelihood of anthracnose attacking. The funds can spread by spores from one leaf to the next or by rain splashing the spores onto to the unaffected leaves. It can take as long as two weeks for your plant to show the first signs. The disease is particularly seductive and the leaves may look fine until you start noticing more and more spots. The fungus attacks the leaves' tissue and devours it, leaving areas on the leaves that are lighter than the rest of the leaf or have bronzed or brownish color.

Keep your plants in full sun as this will make the metalized areas show up quickly. If you see the spots near the end of a branch, be sure to inspect the buds for lesions.

Life Cycle Of Anthracnose

This fungus has four known causal agents, of which the most common is Glomerella cingulata. These cause the disease in a variety of plants, some of which are:

  • Tomato
  • Apple
  • Citrus
  • Cucumber
  • Pepper
  • Potato
  • Rhododendron
  • Gardenia
  • Rose

The fungus overwinters on infected plant debris. It is an obligate parasite. In the spring, spores are small, initially white, but they quickly develop into a powdery black over time.

Fungus spores are spread by wind, rain and infected plant material.

Fungal spore development is favored by moist and warm conditions, particularly those with high humidity and stagnant air.

Moisture can also trigger symptoms. Watering can increase susceptibility.

The disease appears as small, dark brown spots with well-defined borders. Blotches are irregular and usually starting on petioles and the edges of leaves. Leaves may brown, wilt, and die as a result of infection. Healthy tissue underneath the infection appears dark, as these portions are still photosynthesizing.

Young leaves and stems can be particularly vulnerable, but the disease may also occur on the fruit itself and cause discoloration of tomatoes and apples.

Symptoms of Anthracnose

Anthracnose is a fungal disease that affects a wide range of plants, including annuals, vegetables, perennials, and shade trees. It is more prevalent in areas where nights are warm and humid. It likes to grow in wet, rainy weather and it thrives when conditions are most favorable for growth.

The fungal spores of the disease land on your leaves and begin to create leaf spots. The spots will grow and merge together until it causes your leaves to wither and die. The infected leaves will drop off, further spreading the fungus to the foliar and root tissues of your plants.

Your plants will be most at risk during the hot summer months. Left untreated, the fungus will spread and harm your plants' overall health.

Early Anthracnose Detection

Treatments & Prevention.

The most common early anthracnose symptoms usually appear in spring or early summer. These are signs of the fungus as it attempts to infect garlic crops during damp, cloudy weather. Early anthracnose symptoms can include brownish-gray spots on the leaves. These spots start small, but quickly expand to reach as much as 10 cm in diameter.

Since the spores of the anthracnose fungus can also overwinter in your garden, it’s a good idea to remove and destroy any whole bulbs (that you don’t plan to plant in future) that may still be out in your garden in late fall. Another way to prevent anthracnose outbreaks in your garden is to cultivate the land thoroughly before sowing your garlic crop each spring.

On top of that, you can also help your garlic plants fend off the early anthracnose infection with a few preventative steps. The best known among these control methods is spacing. When you grow your garlic in a wide bed (at least 30 cm between bulbs), the chances of the disease spreading from plant to plant are smaller. If you’re growing only one row of garlic bulbs, try to plant them so that there is at least 10 cm between them.

Later Anthracnose Progression

Anthracnose is a fungal disease that primarily infects foliage. It's found in all states and affects over 1000 varieties of plants. You're likely to encounter anthracnose on your plants if you live in warmer areas.

Anthracnose usually appears on the underside of the leaf or at the leaf edges. It will have powdery, white, or grayish spores that form on top of the leaves. Plants with the Anthracnose fungus produce small, tan-colored lesions that start as spots or patches. These spots may continue to grow, and become larger blotches.

These blotches are usually darker than the leaf and eventually turn brown. The blotches may also have a more yellowish or grayish center, with the outer edge of the spots being brown. Blisters may also form on infected parts of the leaves. If the blisters burst, a brown to purple brown spore mass will be found inside of the blisters.

Controlling Anthracnose

Anthracnose is a fungus that affects leaves, stems, and buds of many plants. It is also referred to as early blight, leaf spot, leaf rot, etc. The newer leaves are most commonly affected. Eventually the fungus advances into the main stem. Anthracnose is a wind-borne disease that thrives in wet, warm weather conditions. It overwinters in plant debris and on nearby crop residues.

Anthracnose is quite common in cultivated crops, especially during the rainy seasons. It is important to prevent outbreaks before they occur by applying disease control measures at the first sign of trouble. Since it is difficult to determine which plant tissue is infected, it is better to control all diseased tissue to control the disease.

The best control of anthracnose is achieved by enhancing the natural resistance of the crop. This can be done by selecting disease resistant hybrids or cultivars that are more resistant to the disease. Using disease resistant varieties is by far the best option as it is effective and economically sensible.

Other controls consist of planting crops under favorable conditions to reduce disease development. A very good conservation practice for anthracnose control is to plant the crop early to avoid late season infections. Select the planting site wisely for maximum protection. Avoid planting on low and wet areas. Avoid situations where puddles or standing water are a constant problem. These areas can serve as a disease reservoir.

Anthracnose Treatment

When it comes to disease prevention, the best solution is to plant non-susceptible varieties of plants. If you already have infected plants with Anthracnose, then treat the plants to slow down the spread of infection.

If the infection is limited to one part of your plant, then you can spray the infected areas with a fungicide.

For plants that have a lot of leaf surface to cover, use a fungicide that is labeled for use on vegetables.

If you have several infected plants, spray off the entire plant and let it dry.

Be sure to spray all sides of the plant, even the undersides of the leaves.

This is especially helpful if you have a lot of plant leaf surface to cover.

If the infection has already spread to a number of your plants, then you will need to use a systemic fungicide. You spray the fungicide onto the leaves and it moves into the roots. Spray all the plants in your garden, even the unaffected ones. This will help protect against a more widespread infection.

The best time to spray the plants with a fungicide is in the early morning after dew has evaporated off of the plants.

The leaves will have more time to absorb the fungicide and will be better protected.

Preventing Anthracnose

The Basics

Anthracnose is one of the challenges of late summer, and early fall, particularly in areas where rainfall is heavy. The fungus-like organism causes spots and blemishes on leaves of garden plants.

The fungus infects a variety of plants and usually arrives on leaves which already have other damage.

The damage looks like brown or black marks on the leaves.

Spores from fungus will have spread to affected leaves and new damage on clean plants can be spotted quite easily.

This is because the spores will be visible on affected plants. The same spores that cause the spots on plants will be present in the air and on clothing.

The results of attracting spores are rash marks and similar spots on leaves.

So now you have some fungi you may wonder "will I get anthracnose on my plants?"

Here are some easy ways to prevent anthracnose:

Frequently Asked Questions

If you’re a novice gardener or seriously new to the world of plants and flowers, chances are that you’ve probably heard of anthracnose.

This fungal disease is a common problem among non-hardy plants.

It's fairly easy to prevent and treat, and though it is prevalent, it's typically not a serious life-threatening disease.

With the proper care, you can keep your beloved plants free of anthracnose.

In this article, we’ll take a look at how you can identify the condition, the causes, and what you can do.

Q: Can you eat tomatoes with anthracnose?

Anthracnose is a fungal disease of tomatoes that looks like brown to black spots on the surface of the leaves and the fruit. It is caused by soil-borne fungi that is spread by spores. The disease can be triggered by a number of conditions that include excessive soil moisture, scarified or wounded plants, excessive nitrogen fertilizer rates, or temperatures between 80 and 90 degrees Fahrenheit.

Can you eat tomatoes with anthracnose? You sure can, but the fruit has to be eaten when it is still green. Once it starts to turn red, you have more than likely waited too long to harvest it. While the infected tomato can be eaten, it will not be ideal.

Once the plant has been infected by fungi, it is best to prevent the spread of this disease by not allowing the plant to grow in the same location for longer than two years in a row. Tomatoes that are identified as susceptible should be mulched with fresh sawdust to help prevent soil borne fungi. You need to use the wood from hardwood trees and limit the amount applied to two inches. It is also recommended that you avoid watering the plants through overhead irrigation methods. If you do have to water, water lightly and do not water for more than 3 days afterward. This will help keep the soil from staying overly damp and infested with fungi.