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Abstract
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A study conducted to evaluate age-dependently resistance of Helicoverpa armigera larvae to different geographic
nucleopolyhedrovirus (HearNPV) isolates as alone and in combination with a viral biological activity synergist (Tinopal F-
3543). Two native virus isolates (EAZ-I and EAZ-II) collected from East-Azarbaijan province during the year 2010 and a
non-native isolate were evaluated as standard (STD). Results showed that the larval resistance to the virus isolates increased
as the larval age enhanced. In all the treatments, as a larval instar increased, the susceptibility of the larvae was significantly
reduced. The least amount of LC50 value (1.82×102 OB/ml) was related to STD isolate against the early second instars larvae
when combined with Tinopal, and however, the highest LC50 value (1.43×106 OB/ml) was calculated for EAZ-II isolate
against the fifth instars larvae when applied as alone. The least and the highest amounts of LC50 values were achieved by
STD and EAZ-II isolates applied as alone or in combination with Tinopal, respectively. Also, LC50 values calculated for
virus combination with Tinopal were lower than that of the virus alone in all the larval instars. Age-dependent larval
resistance in the fifth instars larvae compared to the second instars were calculated 632.74 and 143.78 times for EAZ-II
isolate when the virus used as alone and in combination with Tinopal, respectively.
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