Skip to content

Papaya stem rot and planting depth

Papaya stem rot (also called foot rot or collar rot) is a soilborne disease caused by several pathogens, principally Phytophthora palmivora, Fusarium solani and Pythium species. It is one of the most damaging field problems of commercial papaya and is closely linked to planting depth and orchard drainage.

Identification and symptoms

Symptoms begin as water-soaked, dark lesions at or just below the soil line. Lesions enlarge upward, girdling the stem; affected plants wilt, the canopy yellows and the trunk collapses, often without obvious foliar symptoms early on. Roots beneath the lesion are decayed. Plants buried below their polybag soil line at transplanting are particularly susceptible because the porous lower stem stays wet against soil during rain or basin irrigation.

Host crops and life cycle

The pathogens are common soil inhabitants and survive on debris, in soil and in alternative hosts. Phytophthora palmivora produces sporangia and motile zoospores in free water and is favoured by warm, wet conditions and waterlogged or compacted soils. Splashing rain or irrigation moves inoculum onto stems.

Damage and economic impact

Outbreaks have been associated with mortalities of 90% or more in young blocks where deep planting and poor drainage coincide. Even moderate stem-rot incidence sharply lowers the productive plant stand and disrupts harvest scheduling.

Management

Standard recommendations integrate cultural and chemical/biological tools:

  • Planting depth: place the seedling such that the polybag soil surface is level with or slightly above the surrounding bed; never bury the collar.
  • Bed and drainage design: raised beds, free internal drainage, organic mulches to prevent rain splash onto the collar.
  • Sanitation: remove and destroy infected plants and tools; avoid moving infested soil.
  • Biocontrol: root-zone application of Trichoderma harzianum / T. viride at around 50 g/plant with farmyard manure.
  • Chemical: protectant fungicide drenches with metalaxyl-MZ, copper compounds or mancozeb during high-risk periods.

These practices complement ringspot management (Papaya Ringspot Virus Management) on tolerant varieties such as Taiwan Red Lady (Papaya Taiwan Red Lady).

See also: Papaya Taiwan Red Lady, Papaya Ringspot Virus Management.

References

  1. Management of Papaya Stem Rot. Krishi Jagran.
  2. Phytophthora Blight of Papaya. University of Hawaii CTAHR.