Management of wilt of pigeonpea caused by Fusarium Udum

Abstract

The wilt caused by Fusarium udum Butler is an important soil borne disease of pigeonpea. Plants get infected at an early stage, symptoms, however, appear at different growth stages depending on the severity of infection. Generally, wilt symptoms appear 4-6 weeks after sowing but become common and pronounced at reproductive stage. The yield loss depends on the stage at which the plants wilt; the yield decline may rise to 100% when wilt occurs at the pre-pod stage. The wilt incidence may range 69-99% and 31-63% in susceptible and moderately susceptible cultivars, respectively. The disease occurs in most of the pigeonpea growing ountries of Asia, Africa, Europe and America, and results to considerable yield loss to the crop particularly in India. The annual yield loss to igeonpea due o wilt in India has been estimated worth of US$ 36 million. newlineThe wilt fungus, F. udum is host specific being pathogenic only on pigeonpea. In addition to soil inhibiting nature, the fungus has also been ound to be seed borne. The fungus produces micro and macroconidia; chlamydospores are formed under unfavorable environmental conditions, both in parasitic and saprophytic phases from the hyphae and conidial cells. The chlamydospores survive during prolonged absence of the host and at the advent of favorable conditions they act as an initial inoculum of the fungus. Being an internal pathogen, initially no symptom appears. At the advanced stage of disease when symptoms appear it becomes difficult to control the disease. This has necessitated to implement management module that prevents infection by the pathogen at initial stage as well as sustains its effectiveness for longer period. Several management tools are available in the market but have some limitations. Fungicides viz., arbendazim, thiram, vitavax and captan are quick in action, but expensive and create numerous environmental hazards. Biological control is an other option for disease management.