Integrated biological control of Eichhornia crassipes (Mart.) Solms at different growth stages.

摘要

Classical biological control of water hyacinth using insect agent Neochetina spp. is constrained in many tropical watershed environments with interrupted host range due to seasonal water flow and complete drying of water during the hot summer months. Accordingly, the need for reinforcing the classical bio-control approach with sustainable short term measures has been realized and studies were undertaken to explore the possibility of integrating the insect agents and the plant product of dried leaf powder of Coleus amboinicus/aromaticus in controlling water hyacinth at different growth stages based on discriminate analysis using data on plant height, leaf area and fresh weight. Among the different inoculation loads of insect agents, releasing the insect agents three/plant registered the highest reduction in fresh weight, chlorophyll and N, P, K content with small (I stage) and medium (II stage) growth stages of Eichhornia crassipes. At large growth stage (III stage) of E. crassipes none of the loads of insect agents was effective in reducing the fresh weight and chlorophyll content. Among the different concentrations of plant product, spraying at 25% registered the cent per cent reduction in fresh weight, chlorophyll and least N, P and K content at both the stages I and II of E. crassipes. No insect mortality was observed in any of the treatments compared.