Hektar

Symptoms (Key Characteristics for Disease Diagnosis)

• Initial Symptom: Discoloration of the veins and wilting of the leaf petioles.
• Field Symptoms:
  • Attack begins with yellowing of the basal leaves, which become necrotic, dry, and progressively moves upward toward the plant's top.
  • At first, only the leaflets on one side of the leaf show symptoms, followed by the entire leaf wilting and yellowing.
• Greenhouse Symptoms:
  • Rapid progression of wilting, leading to withering, drying, and plant death within a few days without loss of leaf color.
• Night Recovery: In the early stages, wilted plants recover at night but worsen during the day under strong sunlight, eventually leading to irreversible wilting.
• Stem Analysis: Cross-sections through the stem show browning of the vascular tissues, also visible in petioles of wilted leaves.
  • In Fusarium wilt, the browning is more intense but less extensive compared to Verticillium wilt.

Factors Favoring Disease Occurrence and Spread

• Pathogen Type: A soil-borne pathogen present in both protected areas (greenhouses) and the field.
• Infection:
  • Occurs through the roots, often facilitated by root injuries, but even uninjured roots are susceptible.
• Favorable Conditions:
  • Soil temperatures around 28ºC.
  • High atmospheric humidity.
  • Soil pH levels of 5-5.6.
  • High nitrogen and low potassium levels in the soil encourage disease progression.

Prevention and Control Measures

1. Resistant Hybrids

• Cultivating Fusarium-resistant hybrids is the most effective preventive measure in solariums.

2. Soil Disinfection (Chemical)

• If growing non-resistant hybrids:
  • Soil disinfection with Nemasol (700 liters/ha, Metam sodium) through the drip irrigation system.
  • Maintain a soil temperature >15ºC for at least three weeks while covering the surface with plastic film. Afterward, remove the film and perform a phytotoxicity test (with lettuce or bean seedlings) before planting.

3. Preventive Treatments

• If soil disinfection was not performed and monoculture is used:
  • Apply preventive treatments with tebuconazole or 375 g/L 8-hydroxyquinoline sulfate (Beltanol) through the drip irrigation system:
    • First treatment at planting.
    • If necessary, apply 1-2 more treatments at 3-4 week intervals at maximum doses.

4. Additional Cultural Practices

• If Fusarium appears in solariums:
  • Light mulching or adding peat to encourage adventitious roots.
  • Frequent light watering and supplemental nutrition (both soil and foliar) to help maintain plant turgor.
  • Use shading nets from the third decade of May until the third decade of August to reduce heat stress.

5. Organic and Ecological Control Measures

• Altosan: A defense inducer applied through the drip system (20 liters/ha in two stages, 21-day intervals). It acts as a "vaccine" by inducing the production of phytoalexins in plants, strengthening their defense against Fusarium.
• Garex B: An ecological product based on garlic extract, applied through drip irrigation at a dose of 5 liters/ha.
• Mimox: A fungistatic product made from Mimosa extract, applied via drip irrigation at 2-3 liters/ha every 12-15 days.

Conclusion

Fusarium wilt in tomatoes is a highly damaging disease, particularly in solariums and greenhouses where it can rapidly kill plants. The disease is best managed by planting resistant hybrids, maintaining healthy growing conditions, soil disinfection, and adopting an integrated pest management approach that includes both chemical and organic control methods.