Evaluation of the Efficacy of Insecticide chlorfluazuron (EC 5%) against Helicoverpa armigera Hub. in Soybean

The soybean pod borer, Helicoverpa armigera (Lep.: Noctuidae) is the most important pest of soybean crop. Its larva feeds on young leaves, terminal and apical buds and pods of the crop and causes damage. In order to introduce new insecticides for chemical control of this pest, present experiment was carried out in a Randomized Complete Block Design with seven treatments in three replications in Mazandaran, Ardabil (Moghan) and Golestan provinces in 2011. The treatments included chlorfluazuron (Atabron® EC 5%), with three doses (500 ml/ha, 75 ml/ha and 1000 ml/ha) as a new insecticide, indoxacarb SC15 (250ml/ha), thiodicarb (1000g/ha), profenofos (2500ml/ha) and control (sprayed with plain water). Insecticide application was carried out when most of the pest eggs were hatched and very young larvae started feeding on the crop. Sampling and counting of the pest larvae were performed 1 day before and 3, 7, and 14 days after the treatments by randomly selecting 10 plants from four middle rows in each plot. Data were analyzed with SAS software, the means were compared using Duncan and the larval mortality was calculated by Henderson-Tilton formula. The results show that there is a significant difference in the percent efficacy among the treatments. The results of all three provinces are similar. The mean comparison of percent lethality based on Duncan test showed that the least larval lethality percentage occurred on the day three after the treatment. Mean comparison of percent efficacy of the tested pesticides in provinces of Ardabil, Mazandaran and Golestan showed that Chlorfluazuron (1000ml/ha) with 89.3%, 74.67%, and 60.05% and indoxacarb SC15 (250ml/ha) with 87.57%, 77.73% and 57.68% ranked first in the group. Chlorfluazuron, 750 ml/ha (83.69%, 60.87%, 35.86%), Chlorfluazuron, 500 ml/ha (75.42%, 53.1%, 40.93%), thiodicarb (75.69%, 45.33%, 34.81%) and profenofos (68.64%, 35.17%, 31.85%) were ranked in the next groups respectively. Chlorfluazuron (1000ml/ha) and Indoxacarb SC15 (250ml/ha) showed the highest efficacy against the larvae and therefore both of them could be recommended for the chemical control of H. armigera in soybean fields.