Aquatic ecosystems throughout the world are threatened by the presence of invasive aquatic plants, both floating and submerged. Some of the aquatic species, such as water hyacinth (Eichhornia crassipes [Mart.] Solms), alligator weed, Alternanthera philoxeroides (Mart.), giant salvinia, Salvinia molesta D.S. Mitchell and water lettuce (Pistia stratiotes L.), Griseb. despite being relatively minor problems in their native range, have become major invaders of aquatic habitats in other parts of the

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... world after having escaped from their natural enemies. Unchecked growth of aquatic vegetation is generally undesirable and reduces the value of the water resource. Despite adopting all control options including manual, mechanical, chemical and classical biological, the problem persists. The current weed management is oriented towards finding approaches that are effective in controlling the weed and reducing environmental contamination from herbicides. Plant pathogens have been gaining increasing attention and interest among those concerned with developing environmentally friendly, effective and compatible approaches for integrated management of the noxious weeds. This paper discusses some of the major microbial agents associated with aquatic weeds and their increasing role in integrated weed management. Pistia stratiotes L., despite being a relatively minor problem in their native range, have become major invaders of aquatic habitat in other regions of the world after having escaped from their natural enemies [3] . The presence of unwarranted aquatic vegetation influences the management of water in reservoirs, manmade canals, river systems and natural waterways, which amount to millions of kilometres/square kilometres of such water bodies around the world [4, 5] . Dense impenetrable infestations restrict access to water, often reduce the usefulness of aquatic bodies for pisciculture [6] and related commercial activities, the use of irrigation canals, navigation and transport, hydroelectric programmes and tourism [7] [8] [9] . They greatly increase water loss through evapotranspiration when they completely cover the surface of a water body [10] and decrease light penetration, which affects the diversity and population of native aquatic flora and fauna in these habitats [11] [12] . Aquatic weeds can assimilate large quantities of nutrients