Does an increase in invertebrate biodiversity in rice fields affect rice water weevil (Lissorhoptrus oryzophilus) populations?

Rice IPM in the U.S. is done mainly with the use of pesticides, plant resistance and cultural practices, but lacks a biological control component.  Here we investigate whether if increasing the diversity of invertebrates in a rice field can effect rice water weevil (Lissorhoptrus oryzophilus) populations.  Two different experimental approaches were used to test this hypothesis.  One added manure to a continuously flooded field and the second used standard growing practices, but used water from an older rice field for its flood water.  No insecticides were used in either treatments or controls for either method.  Plots were sampled by coring, aquatic netting, trapping, floating pitfall traps and sweep netting.  In both experiments, treatments did increase biodiversity, but they failed to significantly affect L.oryzophilus numbers.  Increasing biodiversity in U.S. rice fields is possible, although it fails to exert a controlling effect on rice water weevils.