Fuarium wilt

Fusarium wilt
    Occurrence of serious wilt was reported from Haryana, Punjab, Rajasthan, Uttar Pradesh and West Bengal.
    Causal organism: Fusarium oxysporum f.sp. psidii Prasad, Mehta and Lall. F.solani (Mart.) Sacc.,
    Symptoms:
    • The disease is characterised by yellowing and browning of leaves, discolouration of stem and death of the branches along one side. Sometimes the infection girdles the stem and whole plant may wilt. Leaf necrosis die and the twig barks split.
    Etiology
    • Mycelium is white or pink with a purple tinge. Microconidia are borne on simple phialides arising laterally on the hyphae. Microconidia are oval to ellipsoid, cylindrical, straight to curved and 7 to 10 x 2 to 3 mm. Macroconidia are 3 to 4 septate and 32 to 50 x 3 to 7 um in size. They are fusoid to subulate and pointed at both ends. Sporodochia and spinanodes are present, chlamydospores may be intercalary or terminal.
    • Asexual spores : Micro & macro conidia
    • Vegetative spores : Chlamydospores (Resting spores)
    • Sexual spores : Ascospores borne in ascus
    • Primary source of inoculum: Soil borne inoculum in the form of chlamydospores and infected plant parts.
    • Secondary source of inoculum: inoculums produced on the infected host

    Mode of spread and survival
    • The fungus first colonizes on the surface of the roots and enters the stem tissues at the basal portions near the ground level. It multiplies in vascular region and affects the cortical cells.

    Epidemiology
    • Higher disease incidence is noticed during the monsoon period. The disease appears in August and increases sharply during September - October. It is severe in alkaline soils.
    Life cycle


    Management
    • Dry branches should be cut off and wilted plants uprooted.
    • Soil should be treated with lime or gypsum to make the soil pH 6.0 to 6.5 and balanced nutrition of host reduces severity of the disease when organic nitrogen is supplied.
    • The soil of the pits should be treated with 37 to 40 per cent formaldehyde (45ml of formaldehyde plus 270 ml of water plus 35 kg of soil).
    • This treatment has to be covered with a polythene sheet for at least 15 to 20 days. When traces of formalin disappears, the pits are filled with this soil after planting the tree
    • Soil drenching with Carbendazim @ 1.5 g/lit considerably reduces the disease.

Last modified: Friday, 22 June 2012, 6:19 AM