Zoological Studies

Vol. 45 No. 4, 2006

Larvicidal Efficiency of Aquatic Predators: A Perspective for Mosquito Biocontrol

Ram Kumar and Jiang-Shiou Hwang*

Institute of Marine Biology, National Taiwan Ocean University, 2 Pei- Ning Rd., Keelung, Taiwan 202

Ram Kumar and Jiang-Shiou Hwang (2006) Biological control of mosquito larvae with predators and other biocontrol agents would be a more-effective and eco-friendly approach, avoiding the use of synthetic chemicals and concomitant damage to the environment. Manipulating or introducing an auto-reproducing predator into the ecosystem may provide sustained biological control of pest populations. The selection of a biological control agent should be based on its self-replicating capacity, preference for the target pest population in the presence of alternate natural prey, adaptability to the introduced environment, and overall interaction with indigenous organisms. In order to achieve an acceptable range of control, a sound knowledge of various attributes of interactions between a pest population and the predator to be introduced is desirable. Herein, we qualitatively review a wide range of literature sources discussing the ability of different aquatic predators to control mosquito larval populations in environments where mosquitoes naturally breed. Different predators of mosquito larvae include amphibian tadpoles, fish, dragonfly larvae, aquatic bugs, mites, malacostracans, anostracans, cyclopoid copepods, and helminths. The most widely used biocontrol agents of mosquito populations are the western mosquito fish, Gambusia affinis, and the eastern mosquito fish, G. holbrooki. The effect of these fishes on native faunal composition and their inability to survive in small containers, tree holes etc., which are ideal breeding sites of vectorially important mosquitoes, make them inefficient in controlling mosquito populations. On the basis of larvicidal efficiency, the ability to produce dormant eggs, the hatchability of dormant eggs after rehydration, faster developmental rates, and higher fecundity, various tadpole shrimp can be considered to be ideal control agents in temporary water bodies and rice paddy fields. Among various predators of mosquito larvae, the cyclopoid copepods are efficient, found naturally, are safe for human beings, and are also economical in their application. The mosquito larval selectivity patterns of many cyclopoids, their adaptability to variable aquatic environments which are ideal breeding sites for mosquitoes, their resistance to starvation, and their day-night prey detection ability using hydromechanical signals make them an ideal biocontrol agent. Therefore, there is a need to test the feasibility of cyclopoid copepods by putting them into operational use as ecocompatible means of biocontrol.

Key words: Mosquito predators, Larvivory, Copepod, Dragonfly larvae, Vector control.

*Correspondence: Tel: 886-2-24622192 ext. 5304. Fax: 886-2-24629464. E-mail:Jshwang@mail.ntou.edu.tw