Bean Anthracnose is a fungal infection called Colletotrichum lindemuthianum that originates from seeds and affects various types of beans such as dry beans, snap beans, runner beans, mung beans, cowpeas, and broad beans. This disease primarily targets dry and snap beans, causing significant damage. The presence of seed spots and blemishes resulting from the infection reduces the quality rating and marketability of the beans, leading to financial losses for growers.
Bean Anthracnose Cycle
The fungus can persist on contaminated seeds and crop debris for a minimum of two years, although this duration is influenced by environmental factors. However, the survival rate of the fungus significantly decreases when infected materials are buried in the field and exposed to water. The presence of alternating wet and dry cycles in the soil further reduces the survival of the fungus.
Bean anthracnose is more likely to develop under cool to moderate temperatures, along with prolonged periods of high humidity or free water on the foliage and young pods. Moisture plays a vital role in the development, spread, and germination of spores, as well as in the infection of the plants. A prolonged period of wet conditions is necessary for the fungus to establish its infection.
The time it takes for visible symptoms to appear after infection can range from 4 to 9 days, depending on factors such as temperature, bean variety, and tissue age.
The fungal spores can easily be transported to healthy plants through wind-blown rain, human activity, and machinery movement in contaminated fields, especially when the plants are wet. Frequent rainy weather increases the occurrence and severity of the disease.
Bean Anthracnose Symptoms and Signs
Bean anthracnose can affect various parts of the bean plant, including leaves, stems, and pods.
When seedlings are grown from infected seeds, they often exhibit dark brown to black sunken lesions on their cotyledons and stems.
In severe cases, cotyledons that are heavily infected with the disease tend to wither and die prematurely, leading to stunted growth of the plants. The affected areas can even encircle the stem, resulting in the death of the seedling.
In moist conditions, the lesions on the cotyledons and stems produce small pink masses of spores.
These spores can spread from the cotyledon and stem lesions to the leaves. Typically, the symptoms manifest on the underside of the leaves as dark brick-red to black lesions along the leaf veins.
As the disease progresses, the discoloration becomes visible on the upper surface of the leaves. However, leaf symptoms are often inconspicuous and can be easily overlooked when inspecting bean fields.
The pods exhibit the most noticeable symptoms of bean anthracnose. These symptoms include small blemishes ranging from reddish brown to black and circular lesions with a distinct reddish brown color.
Mature lesions are characterized by a circular border that is reddish brown to black, with a grayish black interior.
Under moist conditions, the interior of the lesions may release pink masses of spores.
In severe cases, infected pods can shrink and become wrinkled, and the seeds they contain are usually infected as well. Infected seeds display brown to black blemishes and sunken lesions.
Bean Anthracnose Management Strategy
To effectively prevent and eliminate bean anthracnose, the following high-quality fungicides are recommended:
- GREEN COP® 500WP at a rate of 50 grams per 20 liters of water.
- ABSOLUTE® 375 SC at a rate of 10 milliliters per 20 liters of water.
To effectively manage and control bean anthracnose, it is recommended to follow the following practices:
- Opt for certified seed, approved seed, or seeds with a proven track record of being disease-free. Using disease-free seed is the most crucial preventive measure.
- Refrain from planting beans in land that has hosted an infected crop for at least two years.
- Whenever possible, remove diseased plants to help restrict the spread of the disease.
- Avoid cultivating or harvesting affected crops during wet conditions to prevent the dissemination of spores.
- Exercise caution not to pack pods that show slight signs of disease, as anthracnose can develop during transportation.
- Minimize unnecessary movement within fields infested with the disease.
- Choose bean varieties that possess resistance against anthracnose for planting.
Here are some helpful tips:
- To control seed coat infections, consider treating seeds with BIODISTINCTION XTRA.
- When conducting foliar sprays, it is recommended to mix the fungicide with INTEGRA at a rate of 3ml per 20 liters of water. INTEGRA acts as a sticker, spreader, and penetrant, enhancing the effectiveness of the fungicide.
- Timely application of fungicides is of utmost importance to achieve effective control.
- To prevent the development of resistance in the fungus, alternate the use of different fungicides throughout the plant’s growing season.