Beans: Identify anthracnose before it reaches the pods.

The management of anthracnose in bean It is crucial during flowering, pod formation, and pod filling, when the disease caused by Colletotrichum lindemuthianum can compromise productivity and seed quality. In mild and humid weather conditions, the risk increases and requires the producer's attention throughout the crop cycle, from January to December.

The disease can cause flower abortion, malformed pods, spots on pods and seeds, and a decrease in commercial yield. According to data released in the technical content presented, prevention combines healthy seeds, resistant or tolerant cultivars, seed treatment, crop rotation, straw management, appropriate sowing time, monitoring, and judicious use of fungicides.

Anthracnose can affect bean plants from the beginning to the end of their cycle, but the economic impacts become more evident during the reproductive stage. At this stage, the plant directs energy to flowers, pods, and grains, structures that can be directly compromised by the pathogen.

The attack can cause flower abortion, irregular pod formation, sunken and darkened lesions, and lower quality seeds. The risk is aggravated by the high variability of the fungus, which presents many physiological races. Dissemination also occurs through infected seeds and crop residues. Areas with continuous bean succession and crops planted with own seeds without analysis or treatment are among the situations that require greater attention.

Bean anthracnose is caused by Colletotrichum lindemuthianum. According to data released in the presented technical content, the fungus can survive both internally and externally in infected seeds. The pathogen also remains in crop residues left on the surface or incorporated into the soil. Spontaneous bean plants and some alternative hosts can also contribute to its survival.

In the field, moderate temperatures, generally between 18°C and 24°C, associated with high relative humidity and prolonged leaf wetness, favor the development of the disease. Frequent rain, fog, and heavy dew can prolong the wetting period of the plants. The problem tends to be greater in very dense crops, where air circulation is reduced.

Learn what symptoms to look for in the pods and leaves.

Crop monitoring should be intensified starting at the beginning of flowering. According to data released in the technical material presented, the first signs may appear in different structures of the bean plant.

On the stems and petioles, streaks or elongated, dark spots may appear, usually with defined and, in some cases, depressed edges. In severe attacks, the branches may break or dry out from the lesions. Dark spots may also appear on the leaf veins, mainly on the underside, which evolve into partial drying.

In the pods, one of the main signs is rounded or elongated lesions, dark brown to almost black in color, with a sunken appearance. Under conditions of higher humidity, fungal fruiting bodies may appear on these areas. Affected seeds show dark and irregular spots, often near the hilum. In addition to losing physical and physiological quality, they can carry the fungus to the next crop.

Anthracnose reduces pod size and compromises grain quality.

During pod formation, the disease can directly affect yield components. Flower and young pod abortion reduces the number of pods that reach harvest.

According to data released in the technical content presented, infected pods may become smaller and deformed, while the grains may exhibit impaired development.

Another impact is related to seed quality. Staining impairs commercial classification and can compromise the use of the material as seed in future plantings. Damaged tissues can also facilitate the entry of other opportunistic pathogens. Under conditions favorable to the fungus, therefore, losses can occur in both yield and the visual standard required by the market.

Decision-making begins with evaluating the origin and quality of the seed. According to data released in the technical material presented, certified seeds accompanied by phytosanitary reports reduce the risk of disease introduction. The history of the area should also be considered. Plots with recurrent anthracnose occurrences require crop rotation and more intensive monitoring during the reproductive stage.

The presence of infected bean plant debris on the surface increases inoculum pressure and should be included in management planning. Climatic conditions are another important factor. Periods with frequent rainfall, heavy dew, and mild temperatures favor infection and sporulation, regardless of the month in which they occur.

Use healthy seeds and preventative treatment.

Prevention begins before flowering. According to data released in the technical content presented, producers should prioritize certified seeds with low or no presence of Colletotrichum lindemuthianum.

Seed treatment with fungicides registered for bean cultivation can also reduce initial infection, delaying or minimizing disease incidence during flowering and pod formation. Choosing cultivars with some level of resistance or tolerance is another available tool. Because the fungus exhibits race variability, resistance is not necessarily total, but it can contribute to reducing severity and delaying disease progression.

Avoiding continuous bean cropping in the same area reduces the possibility of pathogen survival in crop residues. According to data released in the technical material presented, alternating with non-host crops, such as grasses, helps to decrease the inoculum available in the soil and straw. After harvest, proper incorporation of bean residues can accelerate decomposition and reduce fungal survival. In no-till systems, it is necessary to consider the origin of the straw and the disease history of the area. The rotation should be adjusted to avoid inoculum accumulation.

Choosing the right planting window can help prevent flowering and pod filling from coinciding with climatic conditions highly favorable to anthracnose. According to data released in the technical content presented, adequate plant densities also help avoid excessive shading and improve air circulation. This management reduces the wetting period of leaves and pods, decreasing conditions favorable to the disease.

Increase monitoring during pod formation.

From the start of flowering, visits to the crop should be more frequent. The producer needs to look for symptoms in veins, petioles, stems, and pods at different points in the field. Wetter or shady areas deserve special attention, as do the borders.

According to data released in the technical material presented, incidence, which corresponds to the percentage of plants with symptoms, and severity, related to the intensity of the symptoms, help determine the disease pressure. If in doubt, the recommendation is to seek an evaluation from an agricultural engineer.

Fungicides should be used judiciously.

Fungicides registered for the control of anthracnose in common beans can be integrated into management during the reproductive stage. The decision should consider the disease history, climatic conditions, and the initial presence of symptoms in the crop.

According to data released in the technical content presented, any application must use a product registered for the crop and for the target anthracnose, respecting the dose, application interval, spray volume, maximum number of applications, and pre-harvest interval established in the product label. Use must be based on an agronomic prescription issued by a qualified professional. In well-defined areas, localized actions such as targeted applications or intensified monitoring can be evaluated. In intense and advanced infestations, the elimination of highly diseased plants may also be considered, but the decision should be evaluated on a case-by-case basis with technical guidance.

Anthracnose control in beans should not be addressed in isolation. Irrigation management, for example, needs to avoid unnecessary wetting of the aerial parts of the plant, especially at night.

Fertilization should also be balanced. According to data released in the technical material presented, excess nitrogen can promote denser foliage and create a more humid microclimate. Control of other diseases should also be considered. The use of fungicides for different targets should take into account the spectrum of action against anthracnose, avoiding the selection of resistance and optimizing applications.

When fungicide management is involved, the producer must strictly follow the label and package insert instructions and use only products registered for beans and for the target anthracnose.

According to data released in the presented technical content, it is also necessary to use the Personal Protective Equipment (PPE) indicated for preparing the spray mixture, application, and washing of equipment. Handling should avoid contamination of water bodies, permanent preservation areas, and neighboring properties. Empty containers must be disposed of correctly, following collection programs and triple rinsing, when indicated. The agronomic prescription must be obtained and respected, issued by a qualified agronomist.

Before and during the reproductive stage, the producer can check:

• Is the seed used certified and has it been treated with an appropriate fungicide?
• Does the cultivar exhibit any level of resistance to anthracnose?
• Does the area have a history of the disease?
• Has there been any recent crop rotation?
• Is the plant density adequate?
• Is the canopy too closed?
• Do flowering and pod formation coincide with mild temperatures and high humidity?
• Are there symptoms on the veins, petioles, stems, or pods?
• Do the climatic conditions and the area's history justify the use of fungicides?
• Is the chosen product registered and was it prescribed by a qualified professional?
• Does the application respect the dosage, timing, interval, spray volume, and pre-harvest interval?
• Are the appropriate PPEs being used?
• Is there a plan for managing crop residues and crop rotation after harvest?

Protect productivity from the start.

Managing anthracnose in beans during pod formation requires an integrated strategy. Acting only after the pods show spots means missing important preventative measures.

According to data released in the technical content presented, crop protection depends on a combination of healthy seeds, suitable cultivars, seed treatment, crop rotation, crop residue management, planting density and timing, monitoring, and, when necessary, the judicious use of fungicides. The integration of these measures helps to reduce disease pressure, preserve productivity, and maintain the quality of harvested pods and seeds.

This content is for informational purposes only and does not replace the assessment of an agricultural engineer under real field conditions.