infestation of rice varieties to the egg masses of chilo suppressalis walker (lepidoptera: pyralidae) in rice nurseries of mazandaran

abstract striped rice stem borer, chilo suppressalis walker (lepidoptera: pyralidae) is one of the important pests in rice fields of mazandaran. therefore, almost the farmers of northern iran apply several pesticides in nurseries for the pest control; while it is causes environmental risks and damages to human. in this research two different items including, 1- study of egg masses density in nurseries of different varieties, 2- study of egg masses density in nurseries of different localities of mazandaran, were analyzed in order to screening many resistant rice varieties, and evaluation the necessity of chemical control in nurseries. the results indicated that the highest egg masses density was observed on the varieties tarom and fajr, and the lowest density was on kados. mean comparison of egg masses densities in different stages of sampling (7-22 may 2006) indicated that there was not significant difference between the different sampling stages. additionally, egg masses densities had not significant difference in different localities of mazandaran, because the density of egg masses was low in all sampled regions. the main result of this project indicates that egg masses density of c. suppressalis is very low in all nurseries of mazandaran and even without any egg mass in some regions, while several insecticides are applied in the nurseries. therefore, application of insecticides is not necessary in nurseries and on the other hand it will be resulted to increasing the expenses for the rice farmers.