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Abstract
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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 5
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