Basal stem rots
Mycosphaerella spp.
What is Basal stem rot (Mycosphaerella pinodes Phoma medicaginis var.)?
Basal stem rot, also called a black stem or Ascochyta blight, is a fungal disease that affects legume crops. It is caused by multiple pathogens, including Phoma medicaginis var. pinodella, Ascochyta pisi, and Mycosphaerella pinodes. Infected plants show symptoms like blackened and dying stems from the soil line upwards. Leaves stems, and pods may develop severe spots, resulting in reduced yields.
How does Basal stem rot (Mycosphaerella pinodes Phoma medicaginis var.) occur?
Spores can survive for extended periods in the soil as thick-walled chlamydospores and then be transmitted through infected seeds, soil, or plant debris. The disease cycle begins when spores encounter susceptible host plants. Under favorable conditions of moisture and temperature, the spores germinate and penetrate the plant tissues, leading to infection and subsequent reproduction of the pathogens, completing the cycle of disease spread and recurrence.
Symptoms
1 - Effects on Plants
• Infected plants undergo stem tissue blackening, stunted growth, wilting, and eventual death, causing reduced crop yield and quality. • Severe spotting affects leaves, stems, and pods, further diminishing productivity. These detrimental effects result in economic losses for farmers.
2 - Effects on Soil
• The fungal pathogens can survive for extended periods in the soil as thick-walled chlamydospores. This can lead to the persistence of the disease in the soil, increasing the risk of future infections in subsequent plantings of susceptible crops.
Solutions
1 - Prevention
• Pathogen-Free Seed: Use seeds obtained from fields free of disease and refrain from saving seeds from affected fields. • Straw Management: After harvest, either burn or plow under the diseased straw to reduce pathogen survival. • Planting Timing: Opt for midseason to late-maturing varieties or consider delaying planting by two weeks, as this can result in lower disease incidence.
2 - Treatment
• Fungicide Seed Treatments: Fungicides like Captan, Mertect, Nevado, Thiram, Rovral, or Wakil XL are effective in controlling seedborne infections and safeguarding the seeds from fungal diseases. • Foliar Fungicides: Use foliar fungicides to prevent or control disease during the growing season. Effective fungicides include Aprovia Top, Cueva, Endura, OSO 5% SC, Priaxor Xemium Brand, Proline 480 SC, or Strobilurin fungicides on a preventive or curative basis, following label instructions.
