Functional response of different life stages of Hippodamia variegata to 4th instar nymphs of Aphis gossypii under microcosm condition
2010
Mohajeri Parizi, E. | Madadi, H. | Allahyari, H. | Mehrnejad, M. R.
Ladybirds are one of the most important natural enemies of aphids in crop fields and orchrds. Hippodamia variegata (Goeze) is one of the best known of this genus and is found on different crops like Alfalfa and vegetables. It feeds on many different aphid species such as pea aphid and cotton aphid. In this study, semiartificial set-ups (two leaves cucumber seedlings) were used for exploring functional response of 3rd and 4th instar larvae and three days old females of ladybirds to 4th instar nymphs of cotton aphids. The 24-h experiments were conducted at 25 ± 1º C, 60 % R.H. and 16:8 (L:D) photoperiod. Cotton aphid densities were 4, 16, 32, 64, 128 and 150 nymphs. Based on logistic regression, functional response type II was determined for all three life stages. Also, searching efficiency and handling time parameters were: 0.0482 h-1 and 1.0289 h for 3rd instar larvae, 0.0387 h-1 and 0.0231h for 4th instar larvae and 0.0935 h-1 and 0.1112 for adults. In addition, theoretical maximum of predation rate (1/Th) was 0.9719, 43.29 and 8.99 4th aphid nymphs per hour. Results showed that searching efficiency of 3rd instar larvae of H. variegata was high even in relatively complex conditions but 4th instar larvae was the most voracious stage of this predator.
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