Synergistic effects of Azadirachtin and Fanvarlit on larval stage of Spodoptera exigua
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عنوان دوره: سومین کنگره بین المللی حشره شناسی ایران
نویسندگان
Department of Plant Protection, Faculty of Agriculture, Azarbaijan Shahid Madani University, Tabriz, Iran,
چکیده
Beet Armyworm, Spodoptera exigua, is among the key pests of crop plants in Iran. In order to find more eco-friendly controlling method, we tested the combination effects of Azadirachtin and Fanvarlit on the 1st instar larvae in a series of experiments. Azadirachtin was applied at two concentrations including 50 and 100 ppm and Fanvarlit concentrations were 25, 50 and 100 ppm in the experiments. All experiments were conducted using 24-well plate as a replication. The larvae were exposed to treatments by feeding on artificial food mixed with respective concentrations of pesticides. Mortality data were subjected to analysis of variance followed by Duncan's multiple range test. In the combined treatments effects such as synergistic, additive or antagonistic interactions on the pest mortality were determined using a 2 test with the control-corrected data. The expected additive proportional mortality ME for the Azadirachtin-Fanvarlit combinations was calculated by ME = MN + MC (1 - MN), where MN and MC are the observed proportional mortalities. Results from a 2 test, 2 = (MNC- ME)2/ME, were compared to the 2 table value for 1 df. If the calculated 2 value exceeded the table value, a non-additive effect was suspected between two agents. If the difference of MNC- ME had a positive value, a significant interaction was considered synergistic and If negative value, a significant interaction was considered antagonistic. In contrast, if the tabulated value exceeds the calculated 2 value, it represents an additive effect at P < 0.05 after 72 h. Fanvarlit concentrations of 50 and 100 ppm caused 5 and 20% mortalities on larvae. After exposing to Azadirachtin, 25, 35 and 45% mortalities were recorded at 25, 50 and 100 ppm, respectively. The results were synergistic for all combinations of 100 ppm Fanvarlit + Azadirachtin; however, it was antagonistic effect for all 50 ppm Fanvarlit + Azadirachtin treatments. Similarly, synergistic effects were recorded as 37.5, 37.5 and 57.5 for 100 ppm Fanvarlit + 100 ppm Azadirachtin for all recording days (one day interval up to three days). These were significantly higher compared to the assigned values to 100 ppm Fanvarlit + 50 or 25 ppm Azadirachtin combinations. The results showed that the combination of Fanvarlit and Azadirachtin have potential for the control S. exigua compared to single usage of each product and could help reduce the usage of synthetic insecticides in pest management. Nevertheless, complementary greenhouse and field tests are proposed for further understanding of the performance of combined plant protection material against S. exigua.
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