Functional response and life history parameters of

Authors: Elie A Dannon Manuele Tamò Arnold van Huis Marcel Dicke

Publish Date: 2010/01/22

Volume: 55, Issue: 3, Pages: 363-378

PDF Link

Abstract

The legume pod borer Maruca vitrata Fabricius Lepidoptera Crambidae is a serious pest of cowpea in WestAfrica The parasitoid Apanteles taragamae Viereck Hymenoptera Braconidae that originates from Taiwan is a potential candidate for biological control of M vitrata We investigated under laboratory conditions the functional response of the parasitoid by offering each experienced female 10 20 30 and 40 larvae of M vitrata We studied the influence of different host larval ages on the development longevity sex ratio lifetime fecundity and parasitization rate of the wasp In a comparative study we also investigated the life history of A taragamae and M vitrata at different temperatures in the range of 20–30°C The parasitoid successfully parasitized two and threedayold host larvae first and second instars Younger larvae onedayold were parasitized to a lesser extent and only males developed in them Older larvae were not parasitized partly because of defensive host behaviour The success of parasitization was positively correlated with the density of twodayold M vitrata larvae Parasitoid developmental time and longevity decreased with increasing temperature The intrinsic rate of population increase r m exhibited an optimum curve with a maximum at 24–28°C For the host M vitrata r m was maximal at temperatures of 26–30°C The data are discussed in the context of the potential of A taragamae for biological control of M vitrataMaruca vitrata Fabricius Lepidoptera Crambidae is one of the key insect pests of cowpea causing up to 80 of yield loss Nampala et al 2002 It originates from the IndoMalaysian region and is a key pest of grain legumes in the tropics and subtropics Tamò et al 1997 Taylor 1978 The crambid develops without diapause and relies on alternate host plants to maintain its population during the cowpea offseason Arodokoun et al 2003 Bottenberg et al 1997 Taylor 1978Control of M vitrata in cowpea has mainly been achieved by using synthetic insecticides Sharma 1998 Kamara et al 2007 Besides chemical control cultural practices and moderately resistant varieties have been developed Kamara et al 2007 However cultural practices and improved varieties still require supplemental applications of synthetic pesticides in order to obtain a substantial yield increase Sharma 1998 This situation often results in an overuse of chemicals with side effects such as pest resurgence and secondary pest outbreaks insecticide resistance environmental pollution and increased human health risks Ekesi 1999 Therefore it appears important to investigate other environmentally benign control methods that can regulate the populations of the legume pod borer Of these classical biological control remains an attractive option in particular after Apanteles taragamae Viereck a solitary endoparasitoid was recorded attacking M vitrata larvae Huang et al 2003The wasp was reported parasitizing only M vitrata in Taiwan However some reports about this wasp species indicated that it was gregarious and that it parasitized five other Pyraloidea species in India Peter and David 1990 Mohan and Sathiamma 2007 For that reason we believe that the latter wasp species is likely to be different from the one we have received from Taiwan which is strictly solitary Huang et al 2003 The parasitoid was imported from Taiwan to the International Institute of Tropical Agriculture IITA in Benin for assessing its potential as a biocontrol agent against M vitrata In fact prior to large scale field releases of any biocontrol agent key aspects of its biology and ecology should be understood or evaluated van Lenteren et al 2003 Life history parameters provide useful information on the efficiency of biological control agents particularly when comparing them with the ones of the target pest Development reproduction and survival of parasitoid insects are life history components that depend on physiological and environmental factors Harbison et al 2001 Uçkan and Ergin 2003 These factors can be either abiotic eg temperature relative humidity or biotic eg size age and density of the hostThe nutritional quality of an insect host is found to be correlated with its body size West et al 1999 Thorne et al 2006 as large hosts contain more resources Uçkan and Ergin 2002 Thus the host size selected for oviposition by a female parasitoid affects the size and sex of its progeny Arthur and Wylie 1959 Jones 1982 King 1987 Dicke 1999 Lacoume et al 2006 In general large adult parasitoids emerge from large hosts and a larger proportion of females are produced when larger hosts are selected by the female parasitoid Dicke 1999 In addition large parasitoid females were found to have more eggs immediately available upon emergence or to be able to generate them when needed and have longer life expectancy than small females Cloutier et al 2000 However the influence of host size on koinobiont parasitoids is complex Harvey 2005 Larval development of koinobiont parasitoids such as A taragamae after parasitization relies on the growth rate of the host Brodeur and Boivin 2004 Harvey 2005 Pennacchio and Strand 2006 The host stage selected for oviposition by a koinobiont female is primarily based on the first host evaluation Jones 1982 Brodeur and Boivin 2004 There is a host size larval instar threshold below which the female parasitoid rejects the host for parasitization Jones 1982 Brodeur and Boivin 2004 Large hosts can exhibit strong defensive behaviour and this can interfere with the possibility of parasitization Brodeur et al 1998Host density is reported to affect the performance of a parasitoid Uçkan et al 2004 The functional response of a parasitoid can be inversely or positively hostdensity dependent or independent from host density Holling 1959 The type of functional response is another essential factor in the selection of efficient biological control agents How a parasitoid responds to an increasing host population can determine the success of biological controlAbiotic factors such as temperature and relative humidity influence the life history parameters and the performance of biological control agents In classical biological control environmental adaptability of introduced parasitoids is one of the key factors that determine their establishment and effectiveness Kalyebi et al 2006 There is a strong influence of temperature on developmental rate survival and fecundity of parasitoids Taylor 1981 Roy et al 2002 Kontodimas et al 2004 Kalyebi et al 2006 The relationship between temperature and developmental rate has been described as negative and linear over most of the temperature range Campbell et al 1974 Typically development ceases below a lower thermal threshold Above it the rate of development increases with temperature until an optimum is reached Above the optimal temperature the rate rapidly decreases to zero Campbell et al 1974 Brière et al 1999

Keywords: