Hydrilla is a submersed aquatic freshwater plant which grows from shallow waters to water depths of over 20 feet. It is widely distributed in warm areas of the world, and occurs in both dioeceous and monoecious strains. A dioecious female strain of hydrilla was introduced into Florida from Sri Lanka in the early 1950s through the aquarium trade. Hydrilla spread rapidly throughout Florida in the 1970s and 1980s and is particularly problematic in our shallow and naturally nutrient rich lakes. The herbicide fluridone, which was effective at low dosages and with minimal non-target effects, was used extensively since 1980 to manage hydrilla. Unfortunately, over the past 5 years, hydrilla has developed resistance to fluridone, stimulating new interest in the search for potential biological control agents.
- Exploration for natural enemies was conducted in Kenya, Uganda and Burundi from 2006-2009. A tip boring mayfly, Povilla adusta, occasionally attacked a high proportion of plants in Lake Tanganyika, but would not be appropriate as a biological control agent because of its broad host range. Herbivorous fish were also found to feed on hydrilla, but again, are not useful for biological control because of lack of host specificity.
- The biology of a tip mining chironomid of hydrilla, Cricotopus lebetis, was investigated. The midge, which may be adventive in the southeastern USA, was found in several Florida lakes. The midge was able to complete development in several different native and exotic aquatic plants, and even in a non-vascular plant, Chara sp.