Multiple predation effects of Episyrphus balteatus (Dip., Syrphidae) and Hippodamia variegata (Col., Coccinellidae) on Aphis gossypii (Hem.: Aphididae) population

Subject Areas : entomology and othea arthropods

F. Tavoosi Ajvad ¹ , H. Madadi ² , B. Gharali ³ , M. Kazzazi ⁴

1 - Graduated student of Agricultural Entomology, Department of Plant Protection, Faculty of Agriculture, Bu-Ali Sina University, Hamedan, Iran
2 - Department of Plant Protection, Faculty of Agriculture, Bu-Ali Sina University. Hamedan, Iran
3 - Research Center for Agriculture and Natural Resources, Qazvin, Iran
4 - Department of Plant Protection, Faculty of Agriculture, Bu-Ali Sina University. Hamedan, Iran

Received: 2012-01-30 Accepted : 2012-12-31 Published : 2013-05-22

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Abstract :

Although herbivores often encounter with many predator types, most experimental predation studies have focused on the effects of single predator on its prey. Recent researches have presented new insight about the effects of multiple predators on their preys. The effects of different types of predators may affect the population of prey in a quite complex way. To perceiving the influence of combined usage of predators on consumption ratio, we investigated the intraguild predation (IGP) between 3rd instar larvae of Episyrphus balteatus De Geer (Diptera: Syrphidae) with the 2nd and 3rd instar larvae of Hippodamia variegata Goeze (Coleoptera: Coccinellidae) on the sweet pepper seedlings in the presence of 3-days old nymphs of cotton aphid, Aphis gossypii Glover (Hem.: Aphididae). Predator rearing and IGP experiments were carried out under laboratory conditions (22± 2°c, 60±10% RH and 16L: 8D photoperiod). The treatments included 2nd and 3rd instar larvae of H. variegata and 3rd instar larvae of E. balteatus alone, their combinations and control (without predators). All experiments had 10 replicates. The expected and observed proportions of killed aphid were calculated for each treatment. Comparison of these proportions indicated that the probability of aphid predation is reduced in multiple treatments than single usages. In the most cases, the third instar larvae of E. balteatus alone were more efficient than H. variegata 2nd and 3rd instar larvae both in combined and single situations.