effect of different irrigation systems on larval infestation of agrotis spp., spodoptera exigua hb. and spodoptera litorallis bois in sugar beet fields

in order to improve the efficiency of irrigation systems and investigate their impact on the pest population levels, furrow and sprinkler irrigation systems were compared in sugar beet fields. in this study, three different fields were chosen and irrigated by one of the furrow, classic and center pivot irrigation systems.  in each field, 20 plots were randomly selected of which 10 plots were marked as untreated control and the rest were sprayed with insecticides. during the growing season, the numbers of insect pests were weekly recorded. results of the experiments indicated a significant difference between root yield of sugar beet in furrow irrigation and center pivot irrigation with 71.31 t/ha and 61.36 t/ha, respectively, while no significant difference between furrow and classic irrigation systems was observed.  sugar yield in furrow, classic and center pivot irrigation was 7.92 t/ha, 8.96 t/ha, and 7.39 t/ha, respectively. there was also a significant difference at 5 % level between classic and furrow irrigation but the difference between center pivot system and classic irrigation was not significant. the rate of sugar beet infestation by cutworms (agrotis spp.) and armyworm (spodoptera exigua) in furrow irrigation was 1.146 % and 2.033 %, respectively which was significantly different from classic irrigation (0.858 % and 1.69 %) and center pivot system (0.872 % and 1.692 %). in classic irrigation, the larval population of s. litorallis was 0.932 per plant which was significantly different from furrow irrigation with 0.825 larvae/plant. treated and untreated plots were not significantly affected by the pests in furrow and center pivot irrigation systems, but there was significant difference between root yield of sugar beet in treated plots (71.99 t/ha) and untreated plots (66.92 t/ha) in classic irrigation.