Evaluating the Safety of Insecticides on Beneficial Wasps in Labs and Fields

Greg Howard
13th July, 2024

Evaluating the Safety of Insecticides on Beneficial Wasps in Labs and Fields

Image Source: Natural Science News, 2024

Key Findings

  • The study from the University of Trento, Italy, evaluated the impact of various insecticides on the parasitoid Ganaspis brasiliensis, a biological control agent for the spotted wing drosophila (SWD)
  • Spinosad was found to be highly toxic to G. brasiliensis, causing 92.5% mortality, making it unsuitable for integrated pest management (IPM) programs
  • Cyantraniliprole was the least toxic insecticide tested, showing potential as a selective pesticide compatible with IPM strategies for SWD
The spotted wing drosophila, Drosophila suzukii (SWD), is a significant pest affecting fruit crops in Europe and America. It has a high adaptability to various environmental conditions, making it a persistent problem for fruit producers[2]. Traditional control methods rely heavily on insecticides, but these can lead to issues such as crop rejections due to exceedance of maximum residue levels (MRLs) and are particularly challenging for organic operations[2]. Integrated pest management (IPM) strategies are being explored to reduce chemical inputs and improve sustainability. A recent study conducted by the University of Trento, Italy, evaluated the susceptibility of the parasitoid Ganaspis brasiliensis (G1 strain) to various insecticides to identify suitable alternatives for integrated pest management of SWD[1]. Ganaspis brasiliensis has been released in Europe and America as a biological control agent against SWD, making it crucial to understand how different insecticides affect this parasitoid. In this study, researchers tested five classes of insecticides: neonicotinoids, diamides, pyrethroids, organophosphates, and spinosyns, both in laboratory settings and field trials in vineyards and sweet cherry orchards. The goal was to evaluate both lethal and sublethal effects on G. brasiliensis. The findings revealed that spinosad exhibited the highest toxicity, with a median lethal concentration (LC50) of 0.00372 of the maximum field dose, and caused 92.5% mortality at initial application (T0) in field trials. This high toxicity makes spinosad incompatible with biological control programs involving G. brasiliensis. Similarly, λ-cyhalothrin showed significant sublethal effects, reducing the longevity of both male and female parasitoids when applied at LC30 levels. In field trials, deltamethrin demonstrated the highest persistence, causing significant parasitoid mortality up to 14 days after treatment. In contrast, cyantraniliprole was found to be the least toxic active ingredient in both topical and residual bioassays. Although its residues caused mortality up to 7 days after treatment in the field, it was still considered a more selective pesticide, making it a potential candidate for integrated management strategies for SWD. These results are consistent with earlier findings on the impact of insecticides on beneficial organisms. For instance, a study on the predator mite Iphiseiodes zuluagai showed that pyrethroids had a prolonged harmful impact compared to neonicotinoids, which were less damaging and more suitable for IPM programs[3]. Similarly, the current study highlights that while some insecticides like spinosad and pyrethroids are highly toxic to beneficial parasitoids like G. brasiliensis, others like cyantraniliprole may be more compatible with IPM strategies. The study also aligns with previous research on the biological control of SWD using parasitoids. Surveys in Asia identified Ganaspis cf. brasiliensis as a promising candidate due to its restricted host range and effectiveness[4]. Further evaluations of its functional response to host densities confirmed its potential as a biological control agent[5]. The current research builds on these findings by providing essential information on how different insecticides affect G. brasiliensis, thereby guiding the selection of insecticides that can be integrated with biological control methods. In conclusion, the study from the University of Trento provides valuable insights into the compatibility of various insecticides with the biological control agent G. brasiliensis. While spinosad and λ-cyhalothrin are highly toxic and thus unsuitable, cyantraniliprole shows promise as a selective pesticide for integrated pest management of SWD. This research underscores the importance of evaluating both lethal and sublethal effects of insecticides to develop sustainable and effective pest management strategies.

AgricultureEnvironmentAnimal Science

References

Main Study

1) Assessment of non-target toxicity of insecticides on Ganaspis brasiliensis (Ihering) in laboratory and field conditions.

Published 12th July, 2024

https://doi.org/10.1002/ps.8271

Related Studies

2) Drosophila suzukii (Diptera: Drosophilidae): A Decade of Research Towards a Sustainable Integrated Pest Management Program.

https://doi.org/10.1093/jee/toab158

3) Sublethal effects of pyrethroid and neonicotinoid insecticides on Iphiseiodes zuluagai Denmark and Muma (Mesostigmata: Phytoseiidae).

https://doi.org/10.1007/s10646-017-1844-x

4) The parasitoid complex of D. suzukii and other fruit feeding Drosophila species in Asia.

https://doi.org/10.1038/s41598-018-29555-8

5) Functional Responses of Three Candidate Asian Larval Parasitoids Evaluated for Classical Biological Control of Drosophila suzukii (Diptera: Drosophilidae).

https://doi.org/10.1093/jee/toz265


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