Fusarium oxysporum f. sp. capsici,

Fungal Disease

Fusarium oxysporum f. sp. capsici,

Fungal Disease

Fusarium oxysporum f. sp. capsici,

Fungal Disease

Fusarium wilt, caused by Fusarium oxysporum, is a soil-borne disease that affects capsicum (bell peppers), leading to wilting, yellowing, and plant death. It can be easily confused with bacterial wilt; however, Fusarium wilt lacks bacterial streaming or ooze. Below is a detailed overview of the disease, including symptoms, research data on fungicides, and management strategies. Fusarium wilt pathogens favor warm temperatures (26°C to 32°C), acidic soils (pH 5.0 to 5.5), and high humidity.

1. Symptoms

• Initial signs include marginal yellowing of leaves and wilting of the entire plant.
• Unlike bacterial wilt, Fusarium wilt does not exhibit bacterial streaming or ooze.
• Internal stem discoloration at the crown region may be seen, but this is not always consistent across plants.

2. Diagnosis

• Fusarium wilt is confirmed through culturing plant samples, as symptoms may mimic other wilting diseases.

3. Research Data on Fungicides*
Several fungicides have been evaluated for their effectiveness against Fusarium oxysporum in capsicum, both under in vitro and field conditions. Here are the key findings:

In vitro Evaluation of Fungicides

• Carbendazim: Complete mycelial growth inhibition at all tested concentrations (50, 100, and 200 ppm).
• Tebuconazole + Trifloxystrobin: Full inhibition at 500 ppm; also effective at lower concentrations, with 95.18% inhibition at 250 ppm and 89.25% at 100 ppm.
• Hexaconazole + Zineb: 88.51% inhibition at 500 ppm concentration.
• Chlorothalonil: 84.44% inhibition at 1000 ppm.
• Azoxystrobin + Difenconazole: 82.96% inhibition at 500 ppm concentration.
• Captan: 79.99% inhibition at 1000 ppm.
• Hexaconazole: Effective even at low concentrations, with 76.66% inhibition at 150 ppm.
• Mancozeb: Less effective, with 51.85% inhibition at 750 ppm and 44.44% at 500 ppm.

Field Evaluation of Fungicides

• Carbendazim and Carbendazim + Mancozeb: Showed no incidence of Fusarium wilt and were statistically superior to other treatments.
• Tebuconazole + Trifloxystrobin: Also highly effective, resulting in no disease incidence.
• Hexaconazole + Zineb and Azoxystrobin + Difenconazole: Both fungicides showed a disease incidence of 15% and 20%, respectively, and were statistically on par.
• Mancozeb: Least effective, with 35% disease incidence.

4. Fruit Yield Data

• Maximum fruit yield (13.0 kg/plot) was recorded with Carbendazim + Mancozeb treatment, followed by Carbendazim (12.0 kg/plot) and Tebuconazole + Trifloxystrobin (11.5 kg/plot).

5. Management Recommendations

• Soil Drenching: Regular soil drenching with Carbendazim has been found effective in inhibiting Fusarium fungal bits at depths of 5 cm.
• Alternating Fungicides: To avoid fungicide resistance in the pathogen, alternating the use of fungicides like Carbendazim, Tebuconazole + Trifloxystrobin, and Azoxystrobin + Difenconazole is recommended.
• Fungicide Mode of Action:
  • Carbendazim belongs to the methyl benzimidazole carbamate (MBC) class and inhibits mitosis by binding to β-tubulin in microtubules, suppressing fungal growth.
  • Triazoles like Tebuconazole, Difenconazole, and Hexaconazole act as demethylase inhibitors (DMIs), interfering with the fungal cell wall structure.
  • Strobilurins like Azoxystrobin and Trifloxystrobin inhibit fungal respiration.

With proper use of fungicides and soil drenching techniques, Fusarium wilt in capsicum can be effectively managed, minimizing disease incidence and improving crop yield.

*Research done at Dr. YS Parmar University of Horticulture & Forestry, Nauni,Solan, Himachal Pradesh, India (~ 1444 ~
Journal of Pharmacognosy and Phytochemistry 2019; 8(5): 1444-1447)