Assistant professor National Taiwan University Taipei, Taipei, Taiwan (Republic of China)
The rice leaffolder (Cnaphalocrocis medinalis) is a major insect pest of rice in Asia, and it caused an average of 18–24% yield losses in rice (Oryza sativa L.). According to the elemental defense hypothesis, the accumulated metals in plant tissues may enhance plant defense against herbivorous insects and pathogens. However, it is unclear whether the exogenous elemental application can induce rice defense to these biotic stressors. Here, we examined the potential of copper (Cu) and iron (Fe) micronutrient supplements for the protection of rice plants against the rice leaffolder. C. medinalis-susceptible rice seedlings were grown under different concentrations of CuSO4 or Fe-citrate, and the effects of elemental treatments on larval growth, as well as on rice growth and yield components were evaluated. Our results showed that intermediate levels of Cu (20 μM CuSO4) and high Fe (265 mg/L Fe) did not inhibit the growth of C. medinalis larvae, but significantly inhibited rice growth and reduced grain yield. A high level of Cu (80 μM CuSO4) was found to inhibit C. medinalis larval growth and pupal development but at the same time adversely affected the growth of rice plants. Prolonged treatment with 10 μM CuSO4 had no adverse effects on rice growth or yield components. These results indicate that pest control based on the application of Cu may be possible through the intervention of nanotechnology to achieve effective larval sublethal and lethal doses.