Compatibility of an insect, a fungus, and a herbicide for integrated pest management ofdioecious hydrilla

摘要

During the past 15 yr dioecious hydrilla (Hydrilla verticillata) in Florida developed resistance to fluridone and endothall, two registered herbicides approved for aquatic use. An integrated pest management approach could mitigate the effects of herbicide resistance and improve the sustainability of dioecious hydrilla management in Florida. In this study, we tested a reduced-risk method for dioecious hydrilla control by integrating selective insect herbivory with a disease organism or low concentrations of a new herbicide recently registered for aquatic use. Two rates of the fungal pathogen Mycoleptodiscus terrestris (Mt) and the acetolactate synthase-inhibiting herbicide imazamox, and two densities of the hydrilla tip-mining midge Cricotopus lebetis alone and in combination were randomly applied to aquaria containing established hydrilla plants and replicated three times. Hydrilla shoots in each tank were harvested ~30 d after the treatments were applied. Hydrilla biomass produced in each treatment was compared. Results showed that combining the hydrilla tip-mining midge C. lebetis with either the Mt fungus or herbicide imazamox significantly reduced hydrilla growth and the effects in some treatments were synergistic. Furthermore, C. lebetis wascompatible with the herbicide imazamox; adult emergence of C. lebetis was similar in aquaria treated with imazamox compared with untreated controls. Incorporating biological control agents like Mt and the tip-mining midge C. lebetis into an integrated weed-management strategy could reduce overreliance on herbicides and provide a more sustainable solution to Florida's dioecious hydrilla problem.