Abstract:  【Aim】To clarify the release patterns of 2-ethyl-3,6-dimethylpyrazine, the alarm pheromone of the red imported fire ant, Solenopsis invicta in two different slow-release carriers, the natural rubber plug (NRP) carrier and the PVC pipe (PVCP) carrier, and to verify the results in the field test. 【Methods】A standard curve of the relationship between the dose and peak area of 2-ethyl-3,6dimethylpyrazine was established by using headspace solid-phase microextraction (HS-SPME) and gas chromatogram-mass spectrometry (GC-MS). The release amount and release rates of 2-ethyl-3, 6-dimethylpyrazine at different doses were determined after extraction in these two slowrelease carriers for 15, 30 and 60 min, respectively. 【Results】In NRP carriers, the release rate of 2-ethyl-3, 6-dimethylpyrazine at the same dose gradually slowed down with the increase of extraction time. There were significant differences in the release amount of 2-ethyl-3, 6-dimethylpyrazine at the dose of 10 000 ng between 15 and 30 min, and between 15 and 60 min extraction, and in the release amount of 2-ethyl-3,6-dimethylpyrazine at the dose of 100 000 ng between 60 and 15 min， and between 60 and 30 min extraction. There were significant differences in the release dynamics of 2-ethyl-3, 6-dimethylpyrazine at the same dose among different extraction time. In PVCP carriers, the release rate of 2-ethyl-3, 6-dimethylpyrazine at the same dose was gradually increased with the extraction time. There were significant differences in the release amount of 2-ethyl-3, 6-dimethylpyrazine at the same dose among different extraction time. In the field test, we confirmed that 1 000 ng of 2-ethyl-3, 6-dimethylpyrazine in NPR carriers significantly attracted S. invicta, and with the increase of dose, 2-ethyl-3, 6-dimethylpyrazine showed a significant repellent effect against S. invicta. In PVCP carriers, 10 000 ng of 2-ethyl-3,6-dimethylpyrazine had a significant attractant effect on S. invicta, and with the increase of the dose, 2-ethyl-3, 6-dimethylpyrazine showed a significant repellent effect against S. invicta. 【Conclusion】The release rate of 2-ethyl-3,6-dimethylpyrazine, the alarm pheromone of S. invicta in NRP carriers gradually slows down with the increase of extraction time, while its release rate in PVCP carriers gradually speeds up with the extraction time. Also, 1 000 ng of 2-ethyl-3, 6-dimethylpyrazine used with NRP carriers or 10 000 ng of 2-ethyl-3,6-dimethylpyrazine used with PVCP carriers can be used for the monitoring of S. invicta, and the NRP carrier is more suitable for the rapid detection of S. invicta.

Key words: Solenopsis invicta, alarm pheromone, headspace solid-phase microextraction, slow-release carrier, release pattern