Anthracnose Symptoms In Beans – Managing Bean Plant Anthracnose In Gardens

Anthracnose Symptoms In Beans – Managing Bean Plant Anthracnose In Gardens

Growing beans can be a simple garden exercise for children who are just starting their first gardens or adult gardeners looking to branch out from nursery raised plants. They’re generally hardy, but have a few diseases that can wipe them out rapidly. Anthracnose is one, but this article will help you better understand how to control anthracnose on beans.

What is Anthracnose on Beans?

It can be incredibly rewarding to grow your own food, especially when you start to move beyond the seedlings you can buy at your local nursery. Beans are usually a pretty easy garden plant to grow directly from seed, since they produce abundantly and have few common problems in most areas. Unfortunately, anthracnose in beans can be a serious problem for some gardeners, but there are steps you can take to protect your plants.

Like many fungal plant diseases, anthracnose can present very differently on different types of plants. On beans, anthracnose symptoms may appear at first as black to brown lesions on the cotyledons and stems of plants. As the anthracnose progresses, the lesions spread and pink fungal spores form in their centers. Severely infected plants are sometimes killed or suffer from girdling of leaves and stems; pods and seeds will show distinct circular red-brown lesions.

Anthracnose is primarily a seed-borne disease in beans, but when conditions are wet and temperatures are cool to moderately warm, spores will spread readily to uninfected plants as well. These spores can come from active plant infections nearby or from spores that were lying dormant on bean foliage from past years.

Managing Bean Plant Anthracnose

Treating anthracnose on bean pods is a losing battle. If your pods are already infected, it’s too late to salvage them, though you can slow the spread of anthracnose in your current and future bean plantings. There are no known chemical treatments for anthracnose, but cultural control of bean anthracnose is fairly effective.

First, always allow beans to dry completely before touching or entering a bean planting. Anthracnose spreads rapidly in the presence of water, so by eliminating this important vector you can often protect the plants that haven’t been infected yet. Secondly, be sure to always clean the tools you’re using in the bean garden before using them elsewhere. Spores can hitchhike rides on these gardening implements.

If you’re trying to salvage this year’s harvest, wait for a very dry day and remove as many infected plants as you can find. This will remove potential infection points, giving you a better chance of having some kind of harvest. When anthracnose appears early in the growing season, you can often replace bean plants you’ve pulled with new seed, provided you were careful to collect all the debris. Do not collect seed for sowing next year, since the seeds stand a high chance of vectoring fungal spores.

In subsequent seasons, spread your beans further apart to make it more difficult for raindrops and animals to transmit anthracnose between plants. Also, practicing a two-year crop rotation with a green manure can both help to bulk up the soil and break the infection cycle. There are a few anthracnose-resistant beans on the market, but none are resistant to all anthracnose strains. If you want to experiment with anthracnose-resistant beans, be patient and record your findings so you’ll know which varieties are best suited to your local conditions.


Program Areas

Anthracnose is a worldwide disease of beans caused by the fungus Colletotrichum lindemuthianum. Common bean is very susceptible to this disease, as is tepary bean. Scarlet runner bean, lima bean, and mung bean are somewhat susceptible. Anthracnose is one of the most important bean diseases. It is worse in temperate regions. Under cool (60° F), wet conditions, the disease can cause complete loss. It can cause disease at all stages of plant growth, from seedlings to growing pods.

Symptoms. On seedlings grown from infected seed, symptoms start as small dark brown to black spots on the seed leaves. Rust-colored specks appear on the hypocotyl and enlarge along, and sometimes around, the stem. If the spots grow completely around the stem, the seedling is killed. The spots become sunken and fill with a salmon-colored ooze, which consists of millions of spores.

On established plants, the veins on the underside of the leaves and the petiole can become infected with elongate, somewhat angular, brick-red to purple spots that soon turn dark-brown to black. Spots may sometimes occur on the upper sides of leaves.

On the pods, symptoms begin with small tan to rust-colored spots whi ch enlarge to dark sunken areas surrounded by a slightly raised black ring with cinnamon-colored border. In the center of the spots, there is often a tan to salmon-colored ooze, which consists of millions of spores. Ooze dries to gray-brown to black granules. On the seeds, large or small yellowish-brown sunken spots may form, which turn brown to black. Pods may shrivel and die if infection is severe.

Similar Diseases. Anthracnose is similar to bacterial blights, which may have yellow or white ooze exuding from the spots on the pods, rather than the tan to salmon-colored ooze of anthracnose. Leaf symptoms are different as well.

Prevention. The fungus survives in the seed, so it is important to use certified disease-free seed, or seed that has been hot water soaked or fungicide treated. Use of a three-year crop rotation is recommended. Keep the fields weed free for good air circulation during the season. It is important to plow under bean refuse immediately after harvest as the fungus survives in debris as well. Resistance is available for this disease, but there are several races of the fungus, and it is important to know which races are in the area before varieties are selected for planting.

Contact your local Cooperative Extension center or refer to current recommendations for chemical control measures in the latest New England Vegetable Management Guide.

  • Ntahimpera, N., et al. 1997. Influence of Tillage Practices on Anthracnose Development and Distribution in Dry Bean Fields. Plant Diseases 81:71-76.
  • Schwartz, H.F. 1991. Anthracnose in Compendium of Bean Diseases. R. Hall, ed. APS Press, St Paul, MN. pp. 16-17
  • Sherf, A.F. and A. A. MacNab. 1986. Vegetable Disease and Their Control. John Wiley and Sons, New York.

This information was developed for conditions in the Northeast. Use in other geographical areas may be inappropriate.

By: Pamela S. Mercure, IPM Program Assistant, University of Connecticut, 1998, Reviewed 2012

The information in this document is for educational purposes only. The recommendations contained are based on the best available knowledge at the time of publication. Any reference to commercial products, trade or brand names is for information only, and no endorsement or approval is intended. The Cooperative Extension System does not guarantee or warrant the standard of any product referenced or imply approval of the product to the exclusion of others which also may be available. The University of Connecticut, Cooperative Extension System, College of Agriculture and Natural Resources is an equal opportunity program provider and employer.


Anthracnose is a fungal disease of corn, cucumber, beans, peppers, squash and tomato. It can spread very quickly in warm (80 degrees F), wet weather, especially if air circulation is poor. Fortunately for California gardeners it doesn’t thrive in our hot dry summers.

This disease first appears as small, variously colored, circular spots (those on watermelon are angular) on the older leaves, though it eventually spreads to younger leaves, stems, pods and fruit. The spots enlarge and merge, getting darker until the leaves drop off and the plant is defoliated (or the stem is girdled) and dies. Sunken, round, water-soaked spots appear on fruit.

Anthracnose prevention is easier than cure. Remove diseased plants promptly to minimize its spread. Keep the plants off of the ground on stakes or cages to provide good air circulation. The spores overwinter on volunteers and crop debris, so clear up the beds in fall and rotate your crops. The spores are most often spread via water, when soil containing spores are splashed onto the plants by rain or irrigation. You can reduce this by mulching around the plants and by using drip irrigation. They may also be spread on the hands if the gardener, so don’t touch wet plants (especially not after removing infected plants). Some crop varieties are resistant to Anthracnose.

Anthracnose can also be carried on the surface of the seed, in which case treat them with hot water (127 degrees F for 25 minutes) or bleach solution (1 part bleach to 10 parts water for 30 minutes) to kill the spores.

Image: David B. Langston, University of Georgia, Bugwood.org

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Watch the video: Mango Anthracnose Disease Management