The potential of mass rearing of Monoksa dorsiplana (Pteromalidae) a native gregarious ectoparasitoid of Pseudopachymeria spinipes (Bruchidae) in South America

Abstract

26In Chile and Uruguay, the gregarious Pteromalidae (Monoska dorsiplana) has been 27 discovered emerging from seeds of the persistent pods of Acacia caven attacked by the 28 univoltin bruchid Pseudopachymeria spinipes. We investigated the potential for mass rearing 29 of this gregarious ectoparasitoid on an alternative bruchid host, Callosobruchus maculatus, to 30 use it against the bruchidae of native and cultured species of Leguminosea seeds in South 31 America. 32The mass rearing of M. dorsiplana was carried out in a population cage where the density 33 of egg-laying females per infested seed was increased from 1:1 on the first day to 5:1 on the 34 last (fifth) day. Under these experimental conditions egg-clutch size per host increased, and at 35 the same time the mortality of eggs laid also increased. The density of egg-laying females 36 influenced the sex ratio which tended towards a balance of sons and daughters, in contrast to 37 the sex ratio of a single egg-laying female per host (1 son to 7 daughters). The mean weight of 38 adults emerging from a parasitized host was negatively correlated with the egg-clutch size, i.e. 39 as egg-clutch size increased, adult weight decreased. 40 All these results show that mass rearing of the gregarious ectoparasitoid M. dorsiplana was 41 possible under laboratory conditions on an alternative bruchid host C. maculatus. As M. 42 dorsiplana is a natural enemy of larval and pupal stages of bruchidae, the next step was to 43 investigate whether the biological control of bruchid C. maculatus was possible in an 44 experimental structure of stored beans. 45 46 Key words. Gregarious parasitoid, egg-clutch size, theoretical offspring, observed 47 offspring, sex ratio, bruchid host, Callosobruchus maculatus 48 49 50 1. Introduction 51 52 Bruchids constitute the largest single problem for native and cultured species of 53 Leguminosea seeds in Latin America, attacking a number of economically important plant 54 species. The common bean weevil Acanthoscelides obtectus (Say) and the Mexican bean 55weevil Zabrotes subfasciatus (Boh) are the main post-harvest pests of dry beans and currently 56 constitute a major problem in the management of bean stocks in storage sites (Schmale et al., 57 2001; Alvarez et al., 2005 ). In the last 30 years, these two bruchid species have also been 58 recorded on new host plant species, such as Cajanus indicus, Pisum sativum, Vicia faba, and 59Vigna unguiculata (Jarry and Bonet, 1982; Johnson,1983 Johnson, , 1990. This expansion of host 60 range requires new integrated pest management strategies based on natural resources, 61 including parasitoids. In South America, as in traditional storage systems in the African 62 tropical belt, the parasitoid Dinarmus basalis (Ashm.) is currently the main candidate for the 63 biological control of bruchids in stored beans (Schmale et al., 2001;Sanon et al., 1998; Dorn 64 et al., 2005). 65The challenge now is to find one or more appropriate biological control agents which are 66 native to Latin America. Two nati...

Paracrias pluteus (Hymenoptera, Eulophidae) in Brazil: new distribution and host records, and with a new host group for Paracrias

“…Bruchines ( Coleoptera : Chrysomelidae : Bruchinae ) are considered pests of seeds of native and cultivated legumes in Latin America, causing damage to several economically important agricultural species ( Rojas-Rousse et al 2007 ) such as Glycine max ( Costa et al 2007 ), Phaseolus coccineus , Phaseolus vulgaris , Phaseolus lunatus ( Hansson et al 2004 , Bonet 2008 ), Vigna radiata ( Somta et al 2008 ), Vigna unguiculata ( Aebi et al 2008 ), and tree species such as Enterolobium contortisiliquum ( Morandini and De Viana 2009 ), Melanoxylon brauna ( Santos et al 1991 ), Mimosa bimucronata ( Silva et al 2007 ), Sclerolobium sp. ( Santos et al 1997 ) and Senna multijuga ( Sari and Ribeiro-Costa 2005 ).…”

“…Currently the most efficient method to control these infestations on a large scale is to fumigate the seeds with chemicals ( Sing et al 2008 ), but this method has economic, social and environmental implications ( Somta et al 2008 ). Therefore, control measures including plant resistance ( Ignacimuthu et al 2000 , Schmale et al 2003 , Appleby et al 2004 ), plant extracts with biocide activity ( Raja et al 2004 , Koona et al 2005 ), and natural enemies ( Sanon et al 1998 , Gauthier et al 1999 , Schmale et al 2006 ) such as parasitoids of the families Braconidae , Eulophidae , Pteromalidae ( Schmale et al 2001 , 2002 , Rojas-Rousse et al 2007 ) and Trichogrammatidae ( Pintureau et al 1999 ) constitute more sustainable alternatives.…”