Nutritional and growth indices of Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae) on different corn hybrids

The effect of 11 corn (Zea mays L.) hybrids on the nutritional and growth indices of Helicoverpa armigera (Hübner) was determined under laboratory conditions (25 ± 1 °C, 65 ± 5 % RH and a 16:8 h light:dark photoperiod). The results obtained from the nutritional indices of the whole fourth and fifth instar larvae, on the basis of dry weight, showed that the highest efficiency of conversion of ingested food (ECI) and efficiency of conversion of digested food (ECD) were observed when larvae were fed with hybrid KLM78*MO17. The lowest ECI value was observed in larvae fed with hybrid K36*MO17. The lowest ECD was observed when larvae were fed with hybrid K35*K36. The growth index of overall immature stages varied from 0.021 to 0.062, with the minimum on K48*K18 and the maximum on K47*K19. The standardized insect-growth index and fitness index were highest when larvae were fed with hybrid K47*K19. The lowest standardized insect-growth index was on K48*K18. Also, the lowest fitness index was on K48*K18. Developmental time of the fourth and fifth instars was longest when larvae were fed with hybrid K48*K18. The results of this study indicate that K35*K36 and K48*K18 are unsuitable hybrids for the feeding and growth of the pest.