Nutritional indices of the willow leaf beetle, Plagiodera versicolora Laicharting, third instar larvae and adults were studied on four host plants including Salix alba L., Salix aegyptica L., Populus caspica Bornm.and Populus alba L.at 22 ± 2 ºC, 70 ± 10% R.H., and a photoperiod of 16:8 h (L: D). The results showed that the highest consumed food by the larvae and adults (148.5 ± 18.0 and 175.21 ± 4.51 mg dry weight, respectively) was on P. caspica. The larvae fed on S. alba and S. aegyptica had the highest efficiency of conversion of ingested food (ECI) (2.3 ± 0.33 and 2.23 ± 0.67%, respectively) and efficiency of conversion of digested food (ECD) (2.5 ± 0.35 and 2.41 ± 0.72%, respectively). Approximate digestibility (AD) of larvae was the highest on P. caspica and P. alba (98.51 ± 0.25 and 98.14 ± 0.1%, respectively). The lowest relative consumption rate (RCR) of the larvae and adults was on S. alba (0.14 ± 0.001 and 0.13 ± 0.006 mg/mg/day, respectively). ECI and ECD values of the adults fed on various host plants were not significantly different. Adults fed on P. caspica had the highest values of RCR (0.59 ± 0.01 mg/mg/day), relative growth rate (RGR) (0.02 ± 0.008 mg/mg/day) and AD (98.72 ± 0.24%). These results demonstrated the higher feeding performance of the willow leaf beetle on P. caspica and its poorer performance on P. alba.  

Keywords: nutritional indices, willow leaf beetle, Plagiodera versicolora, host plants

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