Identification, efficacy and population fluctuation of cotton aphid parasitoids
2010
Shahrokhi, Shahram, Iranian Research Institute of Plant Protection | Darvish Mojenni, Taghi | Pourghaz, AbdolHamid | Rezwani, Ali
Aphids are important pests of cotton. They cause yield loss by reducing plant growth, defoliation and excretion honeydew and colonization saprophyte fungi. Parasitoids are important group of aphid natural enemies. In order to identification of cotton aphid parasitoids and evaluation of their efficacy, an experiment was conducted in cotton fields of Gorgan and Varamin regions and Gonbad Agricultural Research Station. Sampling of 50 cotton plants was carried out each week during 2003 and 2004 growing season and aphids and parasitoids were counted on three leaf of each plant.Collected mummies were held in vials until parasitoid emergence and parasitism percent was estimated. Population fluctuation of aphids and parasitoids and their correlation were also studied. Results revealed that Aphis gossypii was dominant aphid species in cotton fields. In Gonbad region, collected aphid parasitoids were belong to genus Aphelinus from family Aphelinidae. Results demonstrated that parasitoids were effective natural enemies of cotton aphids in suitable condition, so that parasitism percent was considerable during growing season (12.5-94%) in Gonbad agricultural research station and the wasps parasitized 56.5 and 62.8 of aphids (in average) in 2003 and 2004, respectively. In conclution, aphid parasitoids of cotton in Gonbad region could be introduce as effective biocontrol agents of cotton aphids duo to their high parasitism rate, significant correlation with host aphid population and host feeding behaviour. However, population of cotton aphid parasitoids, Lysiphlebus fabarum (Aphidiinae, Braconidae), in Gorgan and Varamin regions was low and conservation of this group of natural enemies against pesticides is necessary.
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