Combined effect of nucleopolyhedrovirus and Microplitis pallidipes for the control of the beet armyworm, Spodoptera exigua

Abstract

Control of S. exigua was greater with M. pallidipes plus SeNPV than with M. pallidipes alone. Microplitis pallidipes preferred healthy hosts to infected hosts. Parasitoids were able to complete their development in virus-infected hosts before the hosts died from the virus infection. The parasitoid ovipositors contaminated with the virus could carry and transmit SeNPV.

Effect of nucleopolyhedrovirus infection ofSpodoptera lituralarvae on host discrimination byMicroplitis pallidipes

“…S. litura larvae were reared in sterilised glass containers (10 cm high, 15 cm diameter) on an artificial diet as described by Jiang et al (2011). The parasitoid was allowed to oviposit in early second-instars of S. litura, and hosts were reared on diet until parasitoid cocoons were formed as described by Jiang et al (in press).…”

“…Occlusions of SlNPV were isolated from liquefied cadavers of S. litura and purified by sucrose gradient centrifugation according to Jiang et al (in press). The purified OB were stored at 4°C until use (Jiang et al, 2011). When the experiment was conducted, the purified OB were diluted with distilled water into three different gradients and the OB concentration was determined using a Thomas hemocytometer under a phase-contrast microscope at 400 magnification and to get the required concentrations (1.6 × 10 8 , 1.6 × 10 7 and 1.6 × 10 6 OB·ml −1 ).…”

“…Parasitoid host discrimination behaviours play an important role in helping parasitoids maximise their progeny production by avoiding placing eggs in unsuitable hosts (Nakai, Shiotsuki, & Kunimi, 2005;Wang, Levy, & Daanne, 2013). Some studies have found that parasitoid progeny placed in virus-infected hosts die before their host dies of the viral infection (Hotchkin & Kaya, 1983;Kaya, 1970;Okuno, Nakai, Hiraoka, & Kunimi, 2002), but in other cases parasitoids may finish development before the host dies from virus infection (Hochberg, 1991;Hotchkin & Kaya, 1983;Jiang, Zeng, Ji, Wan, & Chen, 2011). To avoid harm to progeny from development in virus-infected hosts, parasitoids use behaviours to detect and reject infected hosts for oviposition (Stoianova, Hernandez, & Caballero, Caballero, 2007;Versoi & Yendol, 1982).…”

Baculoviruses: Members of Integrated Pest Management Strategies

“…The use of synergism between two different pathogens is a strategy that could be useful to conduct pest control strategies. To evaluate this possibility it have been conducted studies using Spodoptera exigua larvae and assessed the effect of using a baculovirus (Spodoptera exigua NPV) and a parasitoid (Microplitis pallidipes) to control this pest (Jiang et al, 2011). The results obtained indicate that when M. pallidipes-parasitised S. exigua larvae were infected by SeMNPV, the virus did not affect the developmental period of M. pallidipes in the host, and most parasitoids completed development, possibly because parasitism by M. pallidipes reduced larval sensitivity to the virus.…”

“…The results of this study also indicate that M. pallidipes is an important vector of SeMNPV and contributes to natural epizootics of the virus. Female parasitoids that had developed or oviposited in virus-infected hosts, or that emerged from cocoons contaminated with virus, were able to transmit infective doses of virus to healthy host larvae (Jiang et al, 2011).…”