Current control methods for aquatic weeds in New Zealand include mechanical control, herbicides and inundative biological control using sterile grass carp as well as habitat manipulation and integrated control. These options have been used to successfully eradicate weeds (both on a local scale and nationally) and are often highly cost-effective. However, a relatively small number of aquatic weed species have become so widespread that the cost of using these techniques against them can be prohibitive. For example, the annual control costs for hornwort in New Zealand are approximately $3.3 million/yr. A new control method with the potential to reduce these management costs is desirable. In this talk I shall discuss the potential for using classical biological control to tackle some of the worst submerged aquatic weeds in New Zealand.