Notes to broadcasters
In August 2000, farmers and scientists completed a large and important agricultural experiment in China. The study confirmed that crop diversity — planting a mixture of different crops or crop varieties in the same space — helps prevent crop disease. The farmers and researchers were studying a disease called blast (Magnaporthe grisea) — a major fungal disease of rice. Farmers usually control blast by spraying fungicides. The farmers involved in this experiment were able to stop using fungicides to control the disease within two years. The following is a fictional drama highlighting the idea that diversity in the field reduces the incidence of disease. More details about the study in China are provided at the end of the script for those interested in writing their own radio programs about or related to the study. It is important to note that randomly selecting any two varieties of rice will not necessarily provide protection against blast.
SOUND EFFECTS(Sounds of the countryside: roosters crowing, birds singing…).
HOLD SOUND EFFECTS UNDER DIALOGUE.
END SOUNDS OF COUNTRYSIDE. FADE IN MUSIC AND HOLD SOFTLY UNDER NARRATOR.
FADE OUT MUSIC. FADE IN SOUND EFFECTS (Countryside sounds: roosters crowing, birds singing…)
HOLD UNDER DIALOGUE. SOUND OF FOOTSTEPS.
MUSICAL BREAK(Five seconds).
FADE IN SOUND EFFECTS (Sound of footsteps as they walk together).
CONTINUE SOUND EFFECTS UNDER DIALOGUE.
END SOUND OF FOOTSTEPS.
FADE OUT COUNTRYSIDE SOUNDS. FADE IN MUSIC AND HOLD UNDER NARRATIVE.
FADE OUT MUSIC.
Contributed by: Jennifer Pittet, Researcher/writer, Toronto, Canada.
Reviewed by: Christopher Mundt, Professor, Department of Botany and Plant Pathology, Oregon State University, USA.
Between the years 1998 and 2000 farmers and scientists carried out one of the largest agricultural experiments of its kind in the world. The study area covered 100,000 acres of farmland and involved thousands of farmers. It examined the effect of intercropping two varieties of rice on the incidence of blast (Magnaporthe grisea), a serious disease of rice.
Previous to the experiment, farmers were planting large areas of standard hybrid rice. They planted separate smaller plots exclusively with sticky rice, which is a valuable crop, but also very susceptible to blast.
In this experiment, farmers planted in a new way. They planted mixtures of the standard and sticky rice together. Four rows of standard rice were planted, then one row of sticky rice, then four more rows of standard rice, and so on. These fields were compared with fields where only sticky rice was planted. In these pure stands of sticky rice there was a 20% incidence of blast. In the fields where sticky rice was intercropped with standard rice, the incidence of blast was reduced to 1%.
The researchers concluded that in the intercropped fields where there were two kinds of rice, the standard rice plants blocked the spread of the blast fungus which spreads by spores in the wind. The difference in height between the two rice varieties was also a factor. The sticky rice plants are very tall and experienced drier, warmer conditions with their heads above the shorter standard rice plants. Disease is less likely to develop in these dry, warm conditions.
“Chinese farmers fight crop disease with diversity,” Pesticide Action Network Updates Service, August 29, 2000. Pesticide Action Network.
Red de Acción en Alternativas al uso de Agroquímicos, Apartado Postal 11-0581, Lima, Perú. E-mail: email@example.com.
“Simple method found to increase crop yields vastly,” C.K. Yoon, New York Times, August 22, 2000, D1-2.
“Genetic diversity and disease control in rice,” Y. Zhu et al., Nature, 406:718-722, August 17, 2000. Macmillan Publishers Ltd.