Journal of Taiwan Agricultural Research

Author:Ching-Chin Chien* and Shu-Chen Chang

Abstract:

    Closterocerus okazakii (Kamijo) is one of the dominant species in the parasitoids of Liriomyza sativae Blanchard in Taiwan.  In an attempt to increase the availability of the biological control agent of C. okazakii, the influence of storage temperature and duration on this wasp was investigated.  The results of the investigation showed that there was a significant difference in the percent emergence between 0-day-old pupae stored at 7℃ for 1–2 weeks (% emergences of 83.1–90.4%) and the control (% emergence of 97.8%).  However, the percent emergence did not decrease if the 0-day-old pupae were stored at 10℃ for 1–2 weeks.  When the pupae were stored at 7℃ for 1–2 weeks and the emergent wasps were reared at 25℃ with honey and host (L. sativae), the longevity and female proportion were not significantly different from the control; but the offspring production, host-killing capability and proportion host parasitized per fed were significantly decreased by 39.0–50.6、26.5–37.5 and 35.0%.  When the pupae were stored at 7℃ for 3 weeks or 10℃ for 1–4 weeks, the female longevity, offspring production, and host-killing capability were significantly decreased by 29.4–42.2、65.8–72.7 and 42.1–60.6%, respectively, compared to those of the control.  Adults (0-day-old) were fed only with honey at 15 and 25℃ for various periods for the study of storage conditions.  After the end of the storage periods, wasps were kept at 25℃ with both honey and hosts to evaluate their offspring production and host-killing capability.  The results revealed that offspring production and host-killing capability of the wasps significantly decreased by 60.6–68.0 and 26.0–36.2% compared to those of the controls after the adults had been stored at 15℃ for 10-20 days and 25℃ for 10 days, respectively.  Daily oviposition and host-feeding patterns of females after strage were different from the control.  Long-tern storage of pupae and adults of C. okazakii is not recommended.  But if long-term storage is required, the best storage condition is maintaining the 0-day-old pupae at 7℃ for 1–2 weeks, followed by female wasps fed with pure honey at 15 and 25℃ for 10–20 and 10 days, respectively.  The best storage conditions for wasp release as biopesticide are maintaining 0-day-old pupae at 7℃ for 1–2 weeks or 10℃ for 1–4 weeks; and female wasps fed with honey at 15℃ for 10–30 days or 25℃ for 10 days.

Key words:Closterocerus okazakii, Liriomyza sativae, Storage, Fertility, Host-killing capability

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