There's no offseason in the fight to control aquatic weeds in the Sacramento-San Joaquin Delta.

Days after stopping its yearly herbicidal treatment of water hyacinth, state officials started using mechanical harvesting in some troubled spots against the invasive aquatic plant.

The California State Parks Division of Boating and Waterways began using the tactic in the Delta waters on Thursday and will continue until early March, when it can again use the herbicide, according to an agency news release.

The harvesting will be focused in several areas, including Whiskey Slough, Rivers End Marina and Old River in far east Contra Costa County.

Other spots include Stockton's Marina and Waterfront, Fourteen Mile Slough, Village West Marina and Weatherbee Lake near Lathrop. Areas where the hyacinth impairs boater navigation will also be targeted.

Harvesting includes large machinery that collects floating mats of water hyacinth, removes it from the water and places the plant at approved dump sites or drying areas. Depending on weather and permit conditions, harvesters can remove several acres per day, officials said.

For more information on the state's water hyacinth control program, visit www.dbw.parks.ca.gov.

Contact Paul Burgarino at 925-779-7164. Follow him at Twitter.com/paulburgarino.