Disruptive effects of azadirachtin on development of Cotesia congregata in host tobacco hornworm larvae

Abstract

Injection of the insect growth regulator (IGR) azadirachtin into Manduca sexta larvae that were parasitized by Cotesia congregata adversely affected subsequent endoparasite development when the compound was administered prior to the first larval ecdysis of the wasps. Injection of 2.5–10 μg of azadirachtin into newly ecdysed fourth or fifth instar hosts partially inhibited or totally suppressed the first larval ecdysis of the parasites. Instead of initiating rapid growth similar to parasites developing in hosts injected with the solvent carrier (ethanol) only, parasites in azadirachtin‐treated hosts never grew beyond the size normally attained in early terminal stage hosts. The host larvae survived for 2 weeks or longer following injection of azadirachtin, but their parasites never recovered and died encased within one or two exuvial cuticles. The parasitism‐specific hemolymph polypeptides previously shown to be characteristic of terminal stage hosts were undetectable in larvae in which the parasites failed to ecdyse to the second instar. The observed effects of azadirachtin on development of C. congregata differ significantly from those induced by other IGRs in parasitized M. sexta, suggesting azadirachtin has a unique, though as yet undefined, mode of action. Compared to other IGRs, this compound is extremely potent in terms of the minimum doses required to prevent emergence, but affects only the L1‐L2 ecdysis and not the L2‐L3 transition. In contrast, other compounds such as juvenoids and the JH esterase inhibitor BEPAT (S‐benzyl‐0‐ethyl phosphoramidothiolate) permit the parasite to grow and develop normally until the wasps become pharate third instar larvae, then inhibit the second larval ecdysis and emergence from the host.

Toxic effects of the neem oil (Azadirachta indica) formulation on the stink bug predator, Podisus nigrispinus (Heteroptera: Pentatomidae)

“…Studies on the insect growth regulatory mode of azadirachtin action in Calliphora vicina Robineau-Desvoidy (Diptera: Calliphoridae), Manduca sexta Linnaeus (Lepidoptera: Sphingidae), and Oncopeltus fasciatus Dallas (Hemiptera: Lygaeidae), show that JH biosynthesis and catabolism were affected by azadirachtin improving the insect growth regulatory effects505152. Azadirachtin induces supernumerary molts, lack of black pigment and malformations5354. Malformations on the legs, thorax and wings of P. nigrispinus adults exposed to neem oil in the third instar were similar to those found in the coccinellids Chilochorus bipustulatus and Phroscymnus anchorago 55 and the lacewing M. caliginosus 11.…”

Alteration of hemolymph polypeptides in Manduca sexta larvae parasitized by Cotesia congregata: A two‐dimensional electrophoretic analysis and comparison with major bacteria‐induced proteins

“…Host growth, development, and behavior [7,9,11] are altered, and invariably the host is developmentally arrested prior to wandering even if the parasites fail to develop past the first instar [12]. Some physiological changes are initiated immediately after the host is parasitized and are hypothesized to arise via mediation of the polydnavirus injected by the parasite into the host [8].…”

Acute Toxicity of a Neem Seed Kernel based Biopesticide, Nimbecidine Plus on an Edible Fresh Water Crab, Varuna litterata (Fabricius, 1798)

“…al., 1996;Mahboob et al, 1998). The adverse effects of neem based biopesticides on the non-target organisms due to indiscriminate usage were also reported (Schmutterer and Holst 1987;Beckage et al 1988;Price and Schuster 1991;Schöder, 1992;Okpanachi, 1992, 1997;Winkaler et al, 2007;Saravanan et al, 2010Saravanan et al, , 2011Maitra et al, 2014).…”