Combined Non-Target Effects of Insecticide and High Temperature on the Parasitoid Bracon nigricans

Abstract

We studied the acute toxicity and the sublethal effects, on reproduction and host-killing activity, of four widely used insecticides on the generalist parasitoid Bracon nigricans (Hymenoptera: Braconidae), a natural enemy of the invasive tomato pest, Tuta absoluta (Lepidoptera: Gelechiidae). Laboratory bioassays were conducted applying maximum insecticide label rates at three constant temperatures, 25, 35 and 40°C, considered as regular, high and very high, respectively. Data on female survival and offspring production were used to calculate population growth indexes as a measure of population recovery after pesticide exposure. Spinetoram caused 80% mortality at 25°C and 100% at higher temperatures, while spinosad caused 100% mortality under all temperature regimes. Cyantraniliprole was slightly toxic to B. nigricans adults in terms of acute toxicity at the three temperatures, while it did not cause any sublethal effects in egg-laying and host-killing activities. The interaction between the two tested factors (insecticide and temperature) significantly influenced the number of eggs laid by the parasitoid, which was the lowest in the case of females exposed to chlorantraniliprole at 35°C. Furthermore, significantly lower B. nigricans demographic growth indexes were estimated for all the insecticides under all temperature conditions, with the exception of chlorantraniliprole at 25°C. Our findings highlight an interaction between high temperatures and insecticide exposure, which suggests a need for including natural stressors, such as temperature, in pesticide risk assessments procedures.

Citrus peel essential oil nanoformulations to control the tomato borer, Tuta absoluta: chemical properties and biological activity

“…The potential damage and high growth rate of this pest have pushed growers to increase the number of insecticide applications throughout the tomato production cycle 1 . This has led to the rapid development of insecticide resistance 3,4 and has also had a considerable negative impact on non-target organisms, such as natural enemies and pollinators 5–7 . As a consequence, alternative control tools to conventional synthetic pesticides have been tested and/or implemented within tomato Integrated Pest Management (IPM) packages.…”

Selectivity of novel and traditional insecticides used for management of whiteflies on the parasitoid Encarsia formosa

“…Cyantraniliprole was shown to be slightly toxic toward adults of E. Formosa and Bracon nigricans Szépligeti, and harmless to Tamarixia triozae (Burks) when exposed to its residues . Moreover, it did not influence the reproduction of exposed B. nigricans females . However, cyantraniliprole was classified as highly toxic towards E. formosa , Diglyphus isaea (Walker) and Aphidius colemani Viereck following topical application .…”

Residual toxicity of insecticides used in Tunisian citrus orchards on the imported parasitoid Diachasmimorpha longicaudata (Hymenoptera: Braconidae): Implications for IPM program of Ceratitis capitata (Diptera: Tephritidae)

“…Even if we have classified both as slightly harmful for D. longicaudata (IOBC class 2) as in other risk assessment studies (Stark et al, 2004), opinions are still divergent about their compatibility with many biocontrol agents of other plant pests, especially parasitoids with emphasis on its possible trans-generational sublethal side effects (Bueno & Freitas, 2004;Biondi et al, 2012bBiondi et al, , 2013Costa et al, 2014;Abbes et al, 2015). As for the precedent substance, more research is required to determine the sublethal side effects on D. longicaudata.…”