Effect of host change on demographic fitness of the parasitoid, Trichogramma brassicae

Shahzad Iranipour1a, Nahid Vaez2, Ghadir Nouri Ghanbalani2, Rasoul Asghari Zakaria3, Mohammad Mashhadi Jafarloo4

1Department of Plant Protection, Faculty of Agriculture, University of Tabriz, Tabriz, Iran
2Department of Plant Protection, Faculty of Agriculture, University of Mohaghegh Ardabili, Ardabil, Iran
3Department of Plant Breeding, Faculty of Agriculture, University of Mohaghegh Ardabili, Ardabil, Iran
4Agriculture and Natural Resource Research Center of East Azerbaijan Province, Tabriz, Iran

Abstract

Trichogramma brassicae (Bezdenko) is the most important species of Trichogramma parasitoids in Iran. The cotton bollworm, Helicoverpa armigera (Hubner) is a polyphagous insect pest that attacks many crops including cotton, maize, soybean, tomato, etc. The bollworm egg is a suitable target for many Trichogramma species. Factitious hosts such as eggs of the flour moth, Anagasta kuehniella (Zeller) and cereal moth, Sitotroga cerealella (Hubner) are used for mass rearing purposes. But a problem that arises sometimes in laboratory cultures is the development of a tendency toward laboratory hosts following a few generations rearing with them. This may tend to a low efficiency on target pest in field conditions. In this study the possibility of declining efficiency of the parasitoid on target pest by developing such a preference to alternative hosts in previous generations were investigated when the flour moth or cereal moth uses as laboratory host. Two generations of T. brassicae were reared on each of the mentioned hosts and then transferred to H. armigera eggs for two further generations. The intrinsic rate of natural increase as well as other life table parameters were used for monitoring fitness of the parasitoid at successive generations. Even generations were included to determine if previously rearing host affected parasitoid performance. Results revealed that host shift from cereal moth to bollworm caused a sudden fall in population growth parameters (both intrinsic rate of natural increase and net replacement rate). Further rearing on bollworm eggs led to a relapse in both parameters. No similar effect was observed in cultures initiated with the flour moth. As a whole, cereal moth was a more suitable host than flour moth.

Keywords: Helicoverpa armigera, factitious host, life table, host suitability

Correspondence: ashiranipour@tabrizu.ac.ir
Associate Editor: Allen Cohen was editor of this paper.

Received: 18 June 2009 | Accepted: 23 December 2009 | Published: 28 June 2010

ISSN: 1536-2442 | Volume 10, Number 78

Iranipour S, Vaez N, Ghanbalani GN, Zakaria RA, Jafarloo MM. 2010. Effect of host change on demographic fitness of the parasitoid, Trichogramma brassicae. Journal of Insect Science 10:78, available online: insectscience.org/10.78