Corynespora cassiicola is a phytopathogenic fungus that affects several agricultural crops in Brazil.
Known as the cause of target spot, it attacks plants such as soybeans, cotton and cucumber. Symptoms include circular spots on the leaves, with concentric rings and a dark center, leading to defoliation and reduced productivity.
Common names
The disease caused by Corynespora cassiicola It is commonly called target spot. In some cultures, it is also referred to as corynespora spot.
Crops attacked
This fungus has a wide host range, affecting more than 530 plant species. In Brazil, the main crops affected include:
- Soybean: Target spot has become a growing concern, especially in states such as Mato Grosso, Goiás and Minas Gerais. Yield losses of up to 50% have been reported in susceptible cultivars.
- Cotton: the disease has caused significant damage in the main producing regions, such as Mato Grosso and Bahia. The early defoliation resulting from the infection compromises the productivity and quality of the fiber.
- Cucumber: in cucumber crops, target spot can reduce productivity by up to 60%, mainly affecting the leaves and, indirectly, the development of the fruit.
- Tomato: affects leaves, stems and, in severe cases, fruits, compromising quality and productivity.
- Black pepper: the disease is one of the main concerns in producing regions, affecting plant development and production.
- Papaya: causes lesions on leaves and fruits, reducing commercial quality and favoring the entry of other pathogens.
Symptoms
Symptoms vary by culture, but generally include:
- Sheets: circular or irregular spots with concentric rings, resembling a target. The lesions may have a yellowish halo and a dark center. In severe infections, early defoliation occurs.
- Stems and pods (soybeans): reddish-brown lesions may appear, contributing to premature maturation of the plants.
- Fruits (cucumber): Although the fruits are not directly affected, severe infections can lead to deformations and reduction in size due to plant damage.
Etiology
Corynespora cassiicola It is a necrotrophic fungus, capable of surviving in crop residues and infected seeds.
Environmental conditions favorable to its development include temperatures between 25 °C and 30 °C and high relative humidity.
The presence of host weeds and the absence of crop rotation contribute to the persistence and spread of the pathogen.
Control
Effective target spot management involves an integrated approach:
- Use of resistant cultivars: Although there are no fully resistant varieties, choosing less susceptible cultivars can reduce the incidence of the disease.
- Crop rotation: alternating with non-host plants, such as grasses, helps to reduce the inoculum present in the soil.
- Seed treatment: use certified seeds treated with specific fungicides to eliminate the pathogen present.
- Application of fungicides: Fungicides containing carboxamides, triazoles and multisites have shown efficacy, especially when applied preventively and with good foliar coverage.
- Cultural practices: adopt adequate spacing, correct irrigation management and weed control to reduce canopy moisture and limit the spread of the fungus.
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