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

TL;DR

This study demonstrates the feasibility of mass rearing the gregarious ectoparasitoid Monoksa dorsiplana on an alternative host, Callosobruchus maculatus, for biological control of bruchid pests in South American legume seeds.

Contribution

It provides a novel method for mass rearing M. dorsiplana on C. maculatus, facilitating biological control of bruchid pests in legume storage.

Findings

Mass rearing of M. dorsiplana on C. maculatus is feasible in laboratory conditions.

Egg clutch size and sex ratio are influenced by female density during rearing.

Increased egg clutch size correlates with decreased adult weight.

Abstract

In Chile and Uruguay,the gregarious Pteromalidae (Monoksa dorsiplana) has been discovered emerging from seeds of the persistent pods of Acacia caven attacked by the univoltin bruchid Pseudopachymeria spinipes. We investigated the potential for mass rearing of this gregarious ectoparasitoid on an alternative bruchid host, Callosobruchus maculatus, to use it against the bruchidae of native and cultured species of Leguminosea seeds in South America. The mass rearing of M.dorsiplana was carried out in a population cage where the density of egg-laying females per infested seed was increased from 1:1 on the first day to 5:1 on the last (fifth) day. Under these experimental conditions egg-clutch size per host increased, and at the same time the mortality of eggs laid also increased. The density of egg-laying females influenced the sex ratio which tended towards a balance of sons and daughters,in contrast to the sex ratio of a single egg-laying female per host (1 son to 7 daughters). The mean weight of adults emerging from a parasitized host was negatively correlated with the egg-clutch size, i.e., as egg-clutch size increased, adult weight decreased. All these results show that mass rearing of the gregarious ectoparasitoid M.dorsiplana was possible under laboratory conditions on an alternative bruchid host C.maculatus. As M.dorsiplana is a natural enemy of larval and pupal stages of bruchidae, the next step was to investigate whether the biological control of bruchid C.maculatus was possible in an experimental structure of stored beans.