Ultimate Guide to Bean Diseases: Symptoms, Prevention, and Treatment
Phaseolus vulgaris, is also known as the common bean, is a herbaceous annual plant in the Fabaceae family that is farmed as a pulse and green vegetable.
Bean types such as,
- Green peas
- French bean
- Long beans have been cultivated since 6,000 years ago for their fruits or pods for vegetables in various parts of the world.
Here are the tips for growing beans in your garden. This article gives you information about bean diseases.
Bean diseases aren’t limited to types cultivated by one or more groups, but they are constrained by climatic factors. They cause serious damage and loss in various ways; by injuring or killing the growing plants and seedlings, spotting and decaying seeds. These bean diseases can cause serious yield losses in heavily infected bean fields.
Bacterial, Viral, and Fungal Bean Diseases
Bacterial Diseases
There are three main bacterial diseases of common beans: common bacterial blight (Xanthomonas campestris PV. phaseoli), bacterial brown spot (Pseudomonas syringae PV. syringae), and halo blight (Pseudomonas syringae PV. phaseolicola).
Common Blight
Xanthamonas phaseoli are the causative agent, and it thrives in warm, rainy conditions. The pathogen can live on or in the seed, and the infected seed is the pathogen’s major source. The bacterium can also be found in bean plant remnants.
The pathogen has a higher chance of surviving on the surface of the soil than in residues that have been worked into the soil. Uneven brown patches on the leaves, especially towards the borders where there is a thinner border of yellow, are symptoms.
Spots on pods are usually round, somewhat sunk, wet, and dark green. As spots age, they turn a dark red-brown color and get covered with bacterial slime when exposed to high humidity. Stems may be girdled, causing wilting, and stem spots are uncommon. Water-soaked spots turn red-brown, usually without a yellow rim, stems may be girdled, causing wilting, and stem spots are uncommon.
Once the virus has taken hold, the only way to mitigate the harm is to saturate the area with a copper compound. To prevent secondary infection, make sure the sprayer covers the underside of the leaves. However, once common blight has taken hold, you will never be able to eradicate the illness. Use disease-free seeds, resistant cultivars, crop rotation, and avoid overheating irrigation to control common blight.
Halo Blight
Halo blight is a severely devastating disease caused by Pseudomonas syringae PV. phaseolicola that you should avoid at all costs. The most common source of the halo blight bacterium is infected bean seed. In bean seed, the pathogen can live for up to four years.
Bean leftovers from earlier seasons can potentially harbor the virus. Wind-driven rain, overhead irrigation, equipment, and people and animals can all spread the halo blight bacterium. After heavy rainstorms, severe outbreaks of halo blight are common.
The disease is active at temperatures ranging from 16 to 23 oC. The bacterium may be present at 28°C. Even if symptoms do not appear, When the temperature drops, the disease will become active once more.
Bean leaves, pods, and seedlings are all affected by halo blight. Water-soaked patches on the lower surface of the leaf indicate the presence of symptoms. Around the infection spots, a halo of yellow-green tissue forms. Infection foci are usually tiny.
Plants get extensive systemic chlorosis when they have a severe leaf infection. Pod symptoms are often red or brown sores that are sometimes water-soaked. Pod lesions may remain green and have crusty bacterial oozing on the surface as pods grow and turn yellow. If diseases spread to the pod suture, the developing seed may become shriveled or discolored.
Bacterial Brown Spot.
Pseudomonas syringae PV. syringae is a bacterium that can cause diseases in a variety of plants, but only a specific strain causes bacterial brown spots. Pseudomonas syringae PV. syringae is a bacterium that can cause diseases in a variety of plants, but only a specific strain causes bacterial brown spots. Bean leaves and pods are affected by bacterial brown spots.
The lesions are usually round, brown, and necrotic, with a blight yellow zone surrounding them. Lesions fall out of the leaves on occasion, giving them a shot-hole appearance. The tissue is usually not soaked in water or only a little. When a pathogen spreads throughout the body, it can cause stem lesions. The lesions on the pods are round and wet at first. They turn brown and rotten.
Control Of Bacterial Diseases
Preventing bacterial bean illnesses is the most effective method of control. Because these diseases need moisture to reproduce and spread, seeds that have been exposed to summer thunderstorms, low autumn temperatures, and rains, and overhead irrigation are more likely to get contaminated with bacteria.
Choose bean cultivars that are resistant to bacterial illnesses that have afflicted them in the past. The susceptibility of different varieties to different bacterial infections varies substantially. The leaves of some cultivars are highly sensitive to one or more diseases, while the pods may be resistant. Before relocating to disease-free fields, tractors and other equipment used in fields with bacterial illnesses should be properly cleaned and disinfected.
Avoid applying pesticides or cultivating when the leaves are wet to prevent the bacteria from spreading on equipment or in spray water.
Crop residues on the soil surface are the ideal place for all three bacterial pathogens to survive. To encourage decomposition, infested bean wastes should be mixed into the soil promptly after harvest and thoroughly covered. Without bean remains, these bacteria can’t thrive in the soil.
Bean residues on the soil surface do not decompose quickly, allowing bacteria to persist for prolonged periods. Until the crop wastes have completely dissolved, fields with bacterial illnesses should not be used for beans again. Follow a minimum 2-year bean rotation to achieve this. Root-rotting organisms, white and gray molds, and anthracnose can all be reduced with proper rotation.
Viral Diseases
Aphids carry the Bean Common Mosaic Virus (BCMV), Bean Common Mosaic Necrosis Virus(BCMNV), and Bean Yellow Mosaic Virus (BYMV), which can be transferred through seed. BCMV can cause a variety of symptoms.
Leaves with flecked dark and light green patterns; leaves may be deformed; yellow spots may be seen on leaves; plant growth may be slowed. The virus can be found in a variety of crops, ornamentals, and weeds all around the world.
Many of these plants act as virus reservoirs, allowing the virus to survive from season to season. The virus is easily spread manually, as well as through seeds and aphids. For these issues, there are no chemical solutions that are advised. Many of these viruses are spread by aphids, although they can also be spread by seed. As a result, saving seeds from year to year is not a good idea.
The only way to control viral diseases is by using resistant varieties. Crop rotation, early planting, and deep plowing of infected fields are NOT effective in controlling viral diseases.
Fungal Diseases
Cercospora Leaf Spot
Cercospora Leaf Spot is caused by the organism Cercospora sp. It appears as uneven, tan dots on the lower leaves of plants. Excessive leaf drop and plant stunting are symptoms of a severe illness. Infection is worsened by prolonged rain, high humidity, and temperatures between 75 and 85 F.
Planting should be done with disease-free seed. After harvesting, remove all rubbish from the garden. For two to three years, don’t plant beans in the same spot. In the home garden, there are no resistant types or recommended chemicals for this disease.
Rust
Rust is a fungus that causes cinnamon-brown granular patches on leaves and pods. A rust infestation that goes untreated can drastically diminish productivity and finally destroy the crop. Rust fungus spores are carried by the wind and flourish in damp environments.
Cool to moderate temperatures, along with wet circumstances that result in lengthy periods of free water on the leaf surface, stimulate rust growth. Under ideal circumstances, many disease cycles can occur at 10-14 day intervals.
Planting disease-resistant types, using fungicides regularly, rotating crops, and avoiding overhead watering are all part of disease control.
Anthracnose
The fungus Colletotrichum lindemuthianum causes anthracnose, a seed-transmitted infection. Pod infection appears as on the pods as round, reddish-brown to near-black lesions. As the lesions become larger, the patches form a sunken core. The brown, decaying tissues in the middle are swiftly replaced by pink fruiting structures that hold the fungus’ spores.
After then, the fungus may be able to penetrate seeds. When contaminated seeds are sown, they become a source of infection for subsequent crops. Storms, humans, and machinery passing across the field when the plants are moist can readily spread the virus to healthy plants.
If anthracnose is discovered in a field, fungicides can be used to control the disease’s spread. Chemical control, on the other hand, is based on early infection detection and will be useless after the disease has been identified.
Lilani graduated with a bachelor of agriculture, with a specialization in biotechnology from the Wayamba University of Sri Lanka, as well as she is following a Master’s in Molecular Life Sciences. She has a passion for writing and communicating about agriculture topics and loves enthusing people about the botanical world.
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