Acute toxicity and environmental risk assessment of 25% spinetoram water dispersible granules for terrestrial organisms

Spinetoram is a broad-spectrum and highly effective biological pesticide with promising applications in integrated pest management. However, its application or residue in the environment may adversely affect the survival, growth, and reproduction of terrestrial organisms. In order to evaluate the acute toxicity and primary risk of 25% spinetoram water dispersible granules to Japanese quail (Coturnix japonica), honeybee (Apis mellifera L.), silkworm (Bombyx mori), trichogrammatid (Trichogramma ostriniae), seven-spotted ladybird(Coccinella septempunctata) and earthworm (Eisenia foetida), acute toxicity tests and primary risk assessments were performed for the above six non-target terrestrial organisms. The results of the toxicity tests showed that the acute oral median lethal dose (7 d-LD₅₀) of 25% spinetoram water dispersible granules for Japanese quail was 1510.3 mg a.i./kg bw, and the acute oral and acute contact 48 h-LD₅₀ for honeybees were 0.267 and 0.060 μg a.i./bee. The acute median lethal concentration (96 h-LC₅₀) for the silkworms was 0.22 mg a.i./L. The acute median lethal application rate (24 h-LR₅₀) for trichogrammatids was greater than562.5 g a.i./hm², and the acute 13 d-LR₅₀ for ladybirds was greater than 168.75 g a.i./hm². 14 d-LC₅₀ for earthworms was greater than 100 mg a.i./kg dry soil. The results of the risk assessment showed that when 25% spinetoram water- dispersible granules were used at the highest recommended application rate in the spraying scenario, it had acceptable primary risks to birds and soil organisms, and unacceptable risks to bees (risk quotient, RQ = 47), silkworms in spray scenarios for the outermost (RQ = 5636 > 1) and second outermost mulberry trees(RQ = 343 > 1), and for non-target arthropods in -field and off-field exposure scenarios (hazard quotient, HQ_in = 1027 > 5, HQ_off = 24.29 > 5). For unacceptable risks, mitigation measures were proposed to protect non-target environmental organisms. Additionally, field trials were recommended to conduct higher-tier risk assessments to obtain more realistic risk results, thereby reducing uncertainties in the evaluation.