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Guava wilt — wilted tree with yellowing leaves Photo: placeholder pending image-fill pass

Guava wilt (Fusarium / Nattrassia / Gliocladium complex)

Guava wilt is a soil-borne disease complex of Psidium guajava and is the single most important biotic constraint on guava cultivation in the Indo-Gangetic plains. It is caused by a consortium of soil fungi — Fusarium oxysporum f. sp. psidii, Nattrassia mangiferae (= Neoscytalidium dimidiatum), Gliocladium roseum and Macrophomina phaseolina — acting in combination, with composition shifting by site and season. The disease was first recorded at Allahabad (Prayagraj) in 1935 and is now endemic across the major guava belts of Uttar Pradesh, Bihar, Madhya Pradesh, Punjab and Haryana.

Identification and symptoms

The first visible symptom is unilateral chlorosis: leaves on one or two branches turn yellow, droop and die back while the rest of the canopy remains green. Within 4-8 weeks the wilt extends to the whole tree; leaves remain attached and turn brown ("flag" symptom). Fruit on affected branches stop sizing and remain small and hard. Below ground, fine feeder roots blacken and slough; a cross-section of the lower trunk and main roots shows brown discolouration of the wood, vascular browning and frequently a sour fermenting odour. Sudden total wilt within a fortnight is more typical of established trees in heavy black soils after monsoon waterlogging; gradual decline over a season is typical in lighter soils.

Hosts and lifecycle

The pathogen complex survives as chlamydospores and mycelium in soil and in crop residue for several years. Infection occurs through wounds in feeder roots and the root collar, often after waterlogging, nematode damage (root-knot, Meloidogyne incognita) or implement injury. The fungi colonise the xylem, block water transport and cause the wilt symptoms above. The disease is most severe on heavy, poorly drained soils with pH below 6.5 and where guava is replanted into an old guava orchard without a rest period. Spread within an orchard is by infected planting material, irrigation water and contaminated implements; long-distance spread is almost entirely by nursery stock.

Damage and economic impact

Guava wilt typically kills 5-15% of trees in an established orchard each year once it appears; entire orchards have been abandoned in parts of Allahabad, Lucknow, Saharanpur, Sangli and the Krishna delta. Replanting failure is the secondary economic loss: a guava orchard removed for wilt cannot usually be replanted to guava on the same site for at least 5-7 years without recurrence. The disease is the principal driver of the gradual shift of guava production from Uttar Pradesh into newer belts in Madhya Pradesh, Bihar and Andhra Pradesh.

Management

There is no curative chemical treatment for established wilt. ICAR-CISH Lucknow and IIHR recommend integrated management:

  • Healthy planting material: source budded or layered plants from accredited nurseries that index mother trees and use disease-free media.
  • Resistant rootstocks and selections: Chinese guava (Psidium friedrichsthalianum) and P. molle show field tolerance and are used as rootstocks at CISH; among scion selections, Lalit, Shweta and Allahabad Safeda Selection-49 show field tolerance compared with susceptible Sardar (Lucknow-49) and L-49.
  • Cultural: avoid replanting guava into a wilt-affected site for 5-7 years; rotate with non-host crops (cereals, legumes). Maintain orchard drainage and avoid basin flooding; ring-trench irrigation reduces collar-zone waterlogging. Apply 10 kg well-rotted FYM + 1 kg neem cake per tree annually to build antagonistic microflora.
  • Biological: drench root zone with Trichoderma harzianum or T. viride (5 kg/ha enriched in FYM) and Pseudomonas fluorescens (2 kg/ha) twice a year before flowering and after harvest.
  • Chemical: drench with carbendazim 0.1% + copper oxychloride 0.3% (5-10 L per tree depending on age) at first symptom appearance and repeat after 30 days. Remove and burn the worst-affected trees to reduce inoculum.

Sucker control through pruning (Guava Pruning Cycle) and basin sanitation reduce the auxiliary stress that triggers latent infections.

See also: Guava Allahabad Safeda, Guava Arka Kiran Iihr, Guava Pruning Cycle.

Sources

  1. Guava wilt. ICAR-Central Institute for Subtropical Horticulture, Lucknow.
  2. Guava wilt management. National Horticulture Board.
  3. Guava Cultivation Package. ICAR-Indian Institute of Horticultural Research.