Mass releases of Trichogramma ostriniae increase maize production in DPR Korea

摘要

Field-scale experiments were conducted in 2005 and 2006 on three cooperative farms in DPR Korea to evaluate the potential of Trichogramma ostriniae releases to reduce tunnel damage of maize plants caused by the Asian corn borer, Ostrinia furnacalis, and increase grain maize production. When released three times against the first generation of the pest at nominal densities of about 150 000 parasitoids/ha each and another two times against the second generation (in total 750 000 parasitoids/ha), significant effects on all assessed parameters were obtained. In the release plots, a mean parasitism rate of 61% was found, significantly different from the 21.8% found in non-release (control) plots. Furthermore, the number of larvae was significantly reduced in release plots compared to control plots by 63.5% over all farms and both study years. Feeding tunnels caused by the Asian corn borer were reduced in length in the release plots by 64.1%. Finally, we found that fresh yield of maize ears was significantly higher in the release plots compared to control plots. For all farms and both years, the increase in fresh yield was 28.2%. In this paper we are for the first time presenting data in an international journal on the effect of Trichogramma releases on maize production in DPRK. Although T. ostriniae releases at high host densities observed in the present study were not able to completely suppress damage by the Asian corn borer, the yield increase of more than 1 ton/ha indicate that T. ostriniae releases may contribute significantly to stabilize the country's maize production as well as support community efforts to avoid reversion into a food emergency situation.