Abstract: The green slender planthopper, Saccharosydne procerus (Homeptera:Delphacidae) serves as a major alternate host of the egg parasitoid, Anagrus nilaparvatae, an important biocontrol agent of the rice planthoppers. Zizania caduciflora plants bearing numerous parasitized eggs of S. procerus highly promoted the A. nilaparvatae populations for the neighboring rice field, and efficiently suppressed the occurrence of the rice planthopper. In the free choice test, A. nilaparvatae emerged from eggs of either S. procerus or Nilaparvata lugens preferred N. lugens eggs to S. procerus. The parasitism of S. procerus by A. nilaparvatae exceeded 15%, while S. procerus eggs were alone provided. S. procerus could not complete its life cycle on rice, indicating no significant damage of this planthopper to rice. These results suggested that a proper management of rice and Z. caduciflora fields may enhance the efficiency of egg parasitoid, Anagrus spp. To control both rice planthoppers in rice field and S. procerus in Z. caduciflora field.

Key words: Saccharosydne procerus, Anagrus nilaparvatae, host preference, conservation of natural enemy, Zizania caduciflora