Parasitism and Optimization ofHyposoter didymator(Hymenoptera: Ichneumonidae) Rearing onSpodoptera littoralisandHelicoverpa armigera(Lepidoptera: Noctuidae)

Abstract

This study was carried out to improve the rearing methods of endoparasiteHyposoter didymator(Thunberg) for biological control release. The growth and the development ofH. didymatoron the first, second, and third instars ofSpodoptera littoralis(Boisduval) andHelicoverpa armigera(Hübner) under laboratory conditions were investigated. Results indicated thatS. littoraliswas a suitable host for the rearing of H. didymator The development time of the parasite on the second instar of both hosts was almost the same (∼17 d). The age of the female parasite affected the percentage of adult emergence, pupal mortality, and females in the offspring reared onS. littoralishost. The best copulation period ofH. didymatorfemales and males was 36 h that resulted in 51.8% of females in the offspring. The male to female ratio during copulation period, as well as the presence of males after copulation, and the number of host larvae for each parasite female had no effect on parasitism. Results suggested thatS. littoralissecond instar is a suitable host for mass rearing ofH. didymatorparasite, which may improve the use ofH. didymatoras a biocontrol agent.

Compatibility between the endoparasitoid Hyposoter didymator and the entomopathogenic fungus Metarhizium brunneum: a laboratory simulation for the simultaneous use to control Spodoptera littoralis

“…Moreover, the reproductive potential of H. didymator females, over 3 days, was not affected by direct applications of the fungus on parasitoid adults, even at high conidial concentrations (10 7 and 10 8 conidia ml −1 ), as no significant differences in S. littoralis parasitization were scored during this time for any treatment (Table ). As the most productive copulation/egg‐laying period for H. didymator females and males is 36 h after emergence, our results show that fungus‐treated H. didymator females would have plenty of time to parasitize S. littoralis larvae before being killed by the fungus (≈ 4 days after treatment), even if they were inoculated as soon as they emerged. It is worth stressing that direct contact between the fungus and the parasitoid represents the worst‐case scenario under field conditions and could be prevented, or at least reduced, if fungus is applied after parasitization.…”

“…That led us to think that the most crucial factor for the parasitoid, and the reason why a lower parasitization was recorded the first day both in the EFP24 and P24 treatments, was the larval instar of the host. It has been shown that H. didymator only parasitizes second (L2) or third (L3) instar S. littoralis larvae . Earlier and later larval stages are considered as low‐quality hosts because they provide few nutrients and have strong immune responses that prevent parasitoid development .…”

“…They were then placed on sterile wet filter paper in sterile Petri plates, sealed with laboratory film, incubated at 25 °C and inspected for fungal outgrowth . The parasitoid reproductive potential, referred as H. didymator complete parasitism, was represented by the number of emerging parasitoid pupae . Finally, total mortality was expressed as the sum of the two former variables (larvae with fungal outgrowth and larvae showing a complete parasitism) and the rest of S. littoralis larvae, which died not evidencing fungal outgrowth nor complete parasitism, i.e .…”

“…As defense units that modulate the cellular immune responses, hemocytes are a very important component of the insect immune system, and the affection of the immune system of the host may increase its susceptibility to other biocontrol agents . The well‐known efficacy of H. didymator controlling several insect pests, including S. littoralis , have led different authors to emphasize on the interest of developing biocontrol strategies using this parasitoid . Although several authors have reported difficulties rearing this parasitoid, and generally considered time‐consuming and easily biased towards males, the recent development of new rearing methods is leading to a more efficient production which could be used if a commercial H. didymator production is aimed …”

Performance of the newly identified endoparasitoid Cotesia icipe Fernandez‐Triana & Fiaboe on Spodoptera littoralis (Boisduval)

“…Different biological agents such as the entomopathogenic fungi (Ahmed & El‐Katatny, ), entomopathogenic nematodes (Atwa, ; Shairra & Noah, ), viruses (Jones, Moawad, McKinley, & Grzywacz, ) and parasitoids (Depalo, Marchetti, Baronio, Martini, & Dindo, ; Hatem, Shawer, & Vargas‐Osuna, ; Vojtech, Meissle, & Poppy, ) have proven effective against S. littoralis . During surveys of amaranth lepidopteran parasitoids in central Kenya, a new species of Cotesia named Cotesia icipe Fernandez‐Triana & Fiaboe was frequently found parasitizing S. littoralis larvae (Fiaboe, Fernández‐Triana, Nyamu, & Agbodzavu, ).…”