Underwater tiller blades churn up to 8 inches into the sediment and dislodge buoyant Eurasian watermilfoil roots. Floating roots may then be collected from the water. Control with rotovation, generally extends 2 or more growing seasons. Harvesting can be compared to underwater lawn mowing. Plants are cut generally 5 feet below the water's surface, collected by conveyer, and stored until disposal on land.
Harvesting removes surfacing mats and creates open areas of water.
However because of its rapid growth rate Eurasian watermilfoil generally needs to be harvested twice during the growing season. Washington requires that cut plants be removed from the water. The United States Department of Agriculture in conjunction with the Army Corps of Engineers have carried out searches for Eurasian watermilfoil biological control agents in Pakistan, Bangladesh, China, Korea, and Yugoslavia. Several insects have been evaluated, including a number of pyralid moths and several stem-boring weevils. However, many of these insects were found to be non-specific to Eurasian watermilfoil or to offer little potential as effective biological control agents.