To maximize use of available management resources, conduct surveys for hydrilla when water temperatures reach 62.6 °F (17°C) for at least two weeks.
Conduct pre-treatment plant surveys beginning in mid-July to inform the annual treatment plan, as surveys will determine plant locations and will provide input to determine duration and dosage of treatment.
Use contact and systemic herbicides to treat hydrilla. Contact and systemic herbicides are associated with different treatment timing windows and address different aspects of the hydrilla plant. Employ chemical treatment using contact herbicides after tubers have sprouted (late June to July) but prior to the formation of new tubers (late August to November). Tuber sprouting has been documented to be synchronous in the Great Lakes and Northeast and, therefore, should allow for consistent annual treatment timing. In the Great Lakes Basin, time systemic chemical treatments, such as fluridone, which targets vegetative tissues (leaves, stems, or roots) to occur no earlier than mid-June, as systemic herbicides should be applied when tubers are sprouting.
Use bathymetric data to facilitate an accurate determination of water volume. Using this data will help generate treatment plans that will achieve more consistent and evenly distributed herbicide concentrations which is more efficient and cost-effective effective.
Provide herbicide applicators with GIS shapefiles of the areas to be treated that can be downloaded into their GPS systems. Doing so will help to keep herbicide applications in the target area of interest.
Monitoring is critical to assess the rate of plant expansion, inform the components of a treatment plan, and evaluate the efficacy of a treatment plan. Monitoring is critical to obtain an estimate of remaining hydrilla populations after each year of treatment. Monitoring data are also used to inform the development of annual treatment plan, to determine locations, durations, and dosages of herbicide treatments. Annual monitoring should include: