Residual effects and foliar persistence of pesticides used in irrigated rice on the parasitoid Telenomus podisi (Hymenoptera: Platygastridae)
2022
Rakes, Matheus | Pasini, Rafael Antonio | Morais, Maíra Chagas | Zanella, Renato | Prestes, Osmar Damian | Bernardi, Daniel | Grützmacher, Anderson Dionei
We evaluated the lethal and sublethal effects of azoxystrobin, cyhalofop-butyl, and thiamethoxam on Telenomus podisi after spraying rice plants in a greenhouse, as well as the degradation kinetics of these compounds over time. Pesticides were sprayed at 50 and 100% of the maximum field recommended concentration for the crop (MFRC). At 0, 5, 10, and 20 days after application of the treatments (DAAT), T. podisi was exposed to leaves containing dry pesticide residues. On these same dates, rice leaves from each treatment were collected for determination of pesticide residues by UHPLC–MS/MS. Based on the results for mortality, parasitism, emergence, and sex ratio of T. podisi, the effects were grouped using a reduction coefficient (Eₓ) and classified according to the scale of the International Organization for Biological and Integrated Control (IOBC). The fungicide azoxystrobin (at 50 and 100% MFRC) was the only one classified as harmless (Class 1). The herbicide cyhalofop-butyl was classified as slightly harmful (Class 2) to T. podisi until 5 DAAT. The insecticide thiamethoxam (50 and 100% MFRC), up to 5 DAAT, was classified as harmful (Class 4) on T. podisi. Regarding residue, the initial concentrations (0 DAAT) of azoxystrobin, cyhalofop-butyl, and thiamethoxam at 100% MFRC in rice leaves were 102.14, 210.09, and 36.93 mg kg⁻¹, respectively. At 50% MFRC, initial waste was approximately half that extracted at 100% MFRC. The estimated half-lives (DT₅₀) were approximately 17, 4, and 5 days for azoxystrobin, cyhalofop-butyl, and thiamethoxam, respectively. Furthermore, we found a positive correlation between effects and residues.
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