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Plant–herbivore–entomopathogen tri-trophic interactions and biodiversity are relatively understudied topics in ecology. Particularly, the effects of entomopathogens on herbivore-induced plant volat...

Phenoloxidase (PO) catalyses the synthesis of o-quinones, which plays critical roles in the innate immunity of insects. The un-activated form of PO is prophenoloxidase (PPO), which has been widely reported, especially in connection with the immune response of insects to invading organisms or chemicals. However, connection between PPO and challenge by combinations of two biocontrol agents (parasitoids and virus) is not well known. We cloned the cDNA encoding an insect PPO (designated as SePPO1) from the beet armyworm, Spodoptera exigua (Hubner), and studied the response of SePPO to the challenge of Microplitis pallidipes Szepligeti and Spodoptera exigua multiple nucleopolyhedrovirus (SeMNPV). The results indicated that SePPO1 had an open reading frame of 2055 bp. Sequence alignment and phylogenetic analysis showed that SePPO1 shared 51% identity with SePPO2, and the two SePPO genes were positively correlated in mRNA levels, which indicated that they act synergistically. The two SePPOs were mainly e...

We determined the effects of parasitism by Microplitis pallidipes and/or nucleopolyhedrovirus (NPV) infection on protective enzymes in the hemolymph of Spodoptera exigua larvae. We found that concentrations of superoxide dismutase (SOD), catalase (CAT) and peroxidase (POD) were constantly higher within the five observation days after treatment in parasitized/virus-infected than healthy (control) larvae. In parasitized + infected larvae, enzyme levels reduced from day 1 compared to parasitized larvae. Compared to enzyme levels in virus-infected larvae, in parasitized + infected larvae, CAT concentrations were generally lower, while SOD concentrations were significantly lower in the first two days and POD concentrations were lower in the first two days, but higher in following three days. We concluded that joint and separate parasitism and NPV infection promoted the activities of protective enzymes. Our findings also revealed that NPV infection inhibited the activities of protective enzymes induced ...

The physiological effects of nucleopolyhedrovirus (NPV) infection and parasitism by Microplitis pallidipes (Hymenoptera: Braconidae) on the hemocytes of Spodoptera exigua (Lepidoptera: Noctuidae) larvae were examined. We found that compared to healthy (control) larvae, the total hemocyte count (THC) and granulocyte count in parasitized larvae increased 1 day after parasitization and then decreased, while the plasmatocyte count was not significantly affected for the first 5 days but was significantly enhanced on day 6 after parasitization. In parasitized + infected larvae, both the THC and granulocyte counts began be lower from day 1 compared to parasitized larvae, while the plasmatocyte count was generally lower than in parasitized larvae. Compared to the control, THC, and granulocyte counts of virus-infected larvae were higher 1 day after infection. Compared to that in virus-infected larvae, THC and granulocyte counts in parasitized + infected larvae began to decrease from day 1 while the plasmatocyte co...

The behaviour and oviposition of solitary endoparasitoid Microplitis pallidipes Szepligeti (Hymenoptera: Braconidae) were monitored to investigate the ability of the parasitoids to distinguish between nucleopolyhedrovirus (NPV)-infected and noninfected Spodoptera litura Fabricius (Lepidoptera: Noctuidae) larvae. The results indicated that the parasitoid searching time and the time until the first parasitoid attack on infected larvae were greater than those recorded on noninfected larvae; the number of infected larvae attacked by parasitoids, the percent of first attacks and parasitism rate in infected larvae were lower than those on noninfected larvae; and these differences were all significant 3 to 5 days postexposure of the larvae to a dose of 1.6 × 108 occlusion bodies (OB)· ml−1 and significant 4 and 5 days postexposure of the larvae to a dose of 1.6 × 107 OB·ml−1. The lowest dosage (1.6 × 106 OB·ml−1) had no significant effect on the above index values. In a field cage experiment, we found that the p...