Push–pull technology

The push–pull technology is a strategy for controlling agricultural pests by using repellent "push" plants and trap "pull" plants. For example, cereal crops like maize or sorghum are often infested by stem borers. Grasses planted around the perimeter of the crop attract and trap the pests, whereas other plants, like Desmodium, planted between the rows of maize repel the pests and control the parasitic plant Striga. Push–pull technology was developed at the International Centre of Insect Physiology and Ecology (ICIPE) in Kenya and Rothamsted Research, UK [1] by a scientific team led by Dr. Zeyaur Khan.

Pests of cereal crops

Stemborers and the parasitic plant striga are both major problems for cereal crops in eastern and southern Africa. Losses to stemborers can reach 80% in some areas and average about 15-40% in others, while those due to striga range between 30-100% in most of the region. When the two occur together, farmers often lose their entire crop. Spraying with pesticides is not only expensive and possibly harmful to the environment, but usually ineffective as the chemicals cannot reach deep inside the plant stems where stem borer larvae reside. Preventing crop losses from stemborers and striga could increase maize and sorghum harvests enough to feed an additional 27 million people in the region.

The pull

The approach relies on a combination of companion crops to be planted around and among maize or sorghum. Both domestic and wild grasses can help to protect the crops by attracting and trapping the stemborers. The grasses are planted in the border around the maize and sorghum fields where invading adult moths become attracted to chemicals emitted by the grasses themselves. Instead of landing on the maize or sorghum plants, the insects head for what appears to be a tastier meal. These grasses provide the "pull" in the "push–pull" strategy. They also serve as a haven for the borers' natural enemies. Good trap crops include well-known grasses such as Napier grass (Pennisetum purpureum) and Sudan grass (Sorghum vulgare sudanense). Napier grass has a particularly effective way of defending itself against the pests: once attacked by a borer larva, it secrets a sticky substance which physically traps the pest and limits its damage.

The push

The "push" in the intercropping scheme is provided by plants emitting chemicals (kairomones) which repel stemborer moths and drive them away from the main crop (maize or sorghum). The best candidates discovered so far with the repellent properties are members of leguminous genus Desmodium. Desmodium is planted in between rows of maize or sorghum. Being low-growing, it does not interfere with the crops' growth and furthermore has the advantage of maintaining soil stability and improving soil fertility through nitrogen fixation. It also serves as a highly nutritious animal feed and effectively suppresses striga. Another plant showing good repellent properties is molasses grass (Melinis minutiflora), a nutritious animal feed with tick-repelling and stemborer larval parasitoid attractive properties.

See also

• Cultural methods
• Sustainable agriculture
• List of sustainable agriculture topics
• Ecotechnology
• List of companion plants
• List of beneficial weeds
• List of repellent plants

References

• Annual Review of Entomology Vol. 52: 375-400 (January 2007) The Use of Push-Pull Strategies in Integrated Pest Management doi:10.1146/annurev.ento.52.110405.091407
• Verbreitung der Push-Pull Anbaumethoden
• ZDF Abenteuer Wissen: Immunsystem der Pflanzen nutzen - Bio-Strategie für nachhaltige Landwirtschaft - Die Push-pull Methode macht Kunstdünger und Insektengift überflüssig.

External links

• www.push-pull.net