Preventing fungi in seeds and seedlings is essential to ensure healthy development of the crops and avoid economic losses or quality. Whether you are an amateur gardener or a professional farmer, understanding the risks, symptoms y control strategies will allow you to maximize the success of germination and establishment of your plants.
Main fungal diseases in seeds and seedlings
Fungal diseases affect both seeds before germination and during the initial development of seedlings. Among the most relevant pathologies are Damping Off (drowning or falling of seedlings), caused mainly by soil fungi such as Pythium, Phytophthora, Rhizoctonia solani y Fusarium. Other important pathogens include Phomopsissyae, Colletotrichum truncatum, Cercospora kikuchii, Sclerotinia sclerotiorum y Aspergillus flavus, especially in crops such as soybeans, vegetables and fruit trees.
These fungi may be present in the substratum, in tools, in contaminated irrigation water or even remain dormant in non-certified seeds.
Symptoms and infection cycle
Symptoms can occur in two phases: provided y posterior to germination. Before germinating, the seed may rot and lose germination capacity. After germination, the seedlings show constriction y darkening of the neck and root, wet lesions, wilting, and eventually falling. The development of molds of Blancos o gray on the surface of the substrate or plant debris is usually evident in severe infestations.
Planting density, excess humidity, low temperatures, poor ventilation and the presence of decomposing organic matter favor the appearance of these pathogens, which may require replanting entire plots and reduce the performance of future harvests.
Transmission factors and risks
Fungi can be transmitted through:
- Infected seeds: Special attention to uncertified or poorly stored seeds.
- Contaminated substrates: Compacted or reused substrates can host fungal spores.
- Tools and equipment: Undisinfected equipment can be a source of cross-infection between batches.
- Irrigation water: Using contaminated or untreated water increases the risk of pathogen spread.
Comprehensive techniques for fungal prevention
The most effective approach is the comprehensive prevention combining good agricultural practices, chemical control and biological methods:
- Use of certified and healthy seeds: Reduces the incidence of fungi and improves the emergence rate. For more tips on pest and disease control, see our article on plants and pest control.
- Seed treatment: Preventive application of fungicides (carbendazim, thiram, metalaxyl, fludioxonil, sedaxane, among others) or biofungicides with Trichoderma viride, beauveria bassiana or bacteria such as Bacillus subtilis. It also incorporates natural extracts such as Eupatorium cannabinum or powdered cinnamon for desired and environmentally responsible effects.
- Disinfection of substrates, trays and tools: Wash with 2% sodium hypochlorite (bleach), hot water or steam to remove residual spores.
- Humidity and irrigation control: Keep the substrate moist but not saturated, use drip irrigation, and avoid wetting the above-ground parts of the plant. Always water in the morning to promote drying.
- Adequate ventilation and temperature: Avoid closed spaces, pots on the ground, or poorly ventilated areas. It is recommended not to exceed temperatures above 27-30°C and to protect seedbeds from low temperatures.
- Correct spacing: Planting at the proper density improves air circulation and uniformity of growth.
- Crop rotation and solarization: Practice rotation and use solarization (covering the soil with plastic) to reduce persistent inocula.
- Balanced fertilization: Split applications of nitrogen and potassium promote plant vigor and reduce disease.
Recommended remedies and products
- Chemical fungicides: Metalaxyl-M, captan, copper oxychloride, propamocarb, fludioxonil and pathogen-specific mixtures.
- Biological fungicides: Trichoderma spp. or bacteria such as Pseudomonas fluorescens.
- Natural solutions: Cinnamon powder, chamomile infusion, "smoked water" or plant extracts allow for environmentally friendly handling.
Additional cultural measures and integrated control
- Eliminate infected plants when symptoms appear, Destroy crop residue and frequently clean all spaces and materials.
- Apply fertilizers in divided doses, Do not overuse nitrogen and avoid compost and poorly fermented manure in seedbeds.
- Water from the base, Use raised trays and do not plant seedlings too deep.
- Consider modern methods such as industrial seed treatment to ensure precision and effective control against fungi.
The key to keeping seeds and seedlings free of fungi lies in preventive management, the combination of several strategies (chemical, biological and cultural) and the constant observationApplying this knowledge and practices ensures the success of the seedbed and the vigorous development of future crops.