Species Diversity and Population Fluctuation of Heteroptera Predators in Rice Fields of Mazandaran Province, Northern Iran

The predator bugs (Heteroptera) are one of the powerful natural enemies in almost agro-ecosystems which have important role in biological control programs. In attention to presence of diverse pests in rice fields and importance of this crop as the main food in Northern Iran, species diversity and population fluctuation of predator bugs were studied in rice fields of Mazandaran province through 2005 - 2006. In a total, 20 species of predator bugs were collected and identified from rice fields of Mazandaran province. Of the collected species, eight species including, Oncocephalus pilicornis Reuter, Oncocephalus plumicornis (Germar), Reduvius pallipes Klug, Rhynocoris iracundus (Poda) and Coranus cf. niger Rambur of family Reduviidae, Stenodema calcaratum (Fieb.), Orthotylus flavosparsus (C.Sahlb.) of family Miridae, and Brachynema puncticornis Rt. of family Pentatomidae are newly recorded from Iran. The results of population fluctuation indicated that the density of predator bugs increases through the crop season gradually, but application of insecticides causes damage to the density population severely. Also, the population density of predator bugs was varied through a day; the most abundant of population was obtained in hours 10 and 18, because of moderate climate. These beneficial insects rest beyond the rice seedlings and among the weeds around the fields through the hours 12 - 16, because of high temperature and humidity in rice fields. The results of population density of predator bugs on three rice varieties including, Fajr, Khazar, and Nemat indicated that highest density was obtained from Fajr and there was not significant difference between the two other varieties. Since the Fajr is a sensitive variety to C. suppressalis and the pest population density on it is higher than other studied varieties, there is higher density of heteropteran predators on this variety than the two others.