Interaction of the Koinobiont ParasitoidMicroplitis rufiventrisof the Cotton Leafworm,Spodoptera littoralis, with Two Entomopathogenic Rhabditids,Heterorhabditis bacteriophoraandSteinernema carpocapsae

Abstract

Entomopathogenic nematodes are generally considered beneficial organisms. However, they can affect beneficial insects such as parasitoids. The interaction between the entomopathogenic nematodes Heterorhabditis bacteriophora Poinar (Rhabditida: Heterorhabditidae) and Steinernema carpocapsae Weiser, and the parasitoid Microplitis rufiventris Kokujev (Hymenoptera: Braconidae) was investigated in the laboratory. In non-parasitized hosts, Spodoptera littoralis Boisduval (Lepidoptera: Noctuidae) larvae exposed to H. bacteriophora showed a higher percent mortality than those exposed to S. carpocapsae. Both nematodes were able to invade and propagate in non-parasitized S. littoralis larvae and those parasitized by M. rufiventris. Both nematode species reproduced in Microplitis-parasitized hosts, but there was a higher number of nematodes in non-parasitized larvae. S. carpocapsae yielded higher numbers of infective juveniles than H. bacteriophora. Generally, the number of nematodes harvested increased as their host's size increased. The interaction between the nematodes and parasitoid favored the nematodes when the nematodes were inoculated during the parasitoid egg stage or the young parasitoid larvae, thus giving the nematodes a better chance to grow and reproduce, resulting in the death of the parasitoid larvae. Conversely, when the nematodes were inoculated during the late larval instar of the parasitoid, the competition partially favored the wasp, thus giving approximately 50% of the wasps a better chance to develop, emerge, and reproduce, providing evidence that both nematodes and wasps could reproduce in the same host. Egg maturation of female wasps derived from nematode-infected hosts was not significantly different than those from control hosts. The combined application of nematodes and parasitoids may be beneficial if the detrimental effects of the nematodes on the parasitoid could be avoided by precisely timing the application strategies. It is clear that Microplitis larvae and the nematodes share the host larva and engage in a trophic interaction with each other. Intraguild predation is briefly discussed.

Natural Warriors against Stored-Grain Pests: The Joint Action of Beauveria bassiana and Steinernema carpocapsae

“…EPNs have been evaluated in combination with insecticides, biocontrol agents, and parasitoids to increase their efficacy against insect pests [ 49 , 99 , 100 , 101 , 102 , 103 ]. Several factors can influence the interaction between EPF and EPNs, such as the species and strains of EPF and EPNs, the target insect host, application parameters, and environmental conditions [ 49 , 103 , 104 , 105 , 106 , 107 ].…”

Review of entomopathogenic fungi and nematodes as biological control agents of tephritid fruit flies: current status and a future vision

“…Probably, the endosymbiotic rhabdoviruses associated with D. longicaudata may deter EPN species from attacking developing D. longicaudata in hosts, similar to protection of EPNs (in EPN‐killed insects) afforded by the reported scavenger deterrent factors from symbiotic bacteria of EPNs or, perhaps, D. longicaudata is naturally resistant to EPN infections (Simmonds et al, 2016; Hoy, 2019). Moreover, the rapid pupation of third instar A. suspensa to resistant pupae may quickly shield the koinobiont parasitoid D. longicaudata , similar to the protection against EPNs afforded to the braconid parasitoid Microplitis rufiventris (Kokujev) in the late instar of the cotton leafworm Spodoptera littoralis (Boisduval) (Lepidoptera: Noctuidae) (Atwa et al, 2013).…”

Interactions between Entomopathogenic Nematodes and Entomophagous Insects

“…The 3 rd instar larvae of S. littoralis (parasitized with the braconid, Microplitis rufiventris (Kok.)) were treated with H. bacteriophora and S. carpocapsae (1200 IJs/5 parasitized larva/Petri-dish) harboring the egg stage, mid 1 st , 3 rd and late 3 rd instars of the parasitoid [34]. It was found that the percentages of hosts that gave rise to adult parasitoids after treatment with S. carpocapsae were 12, 11, 16 and 53% for egg, mid 1 st , 3 rd and late 3 rd instar of the parasitoid on host larvae, respectively.…”