Push-Pull Farming System
The Push-Pull technology involves use of behaviour-modifying stimuli to manipulate the distribution and abundance of stemborers and beneficial insects for management of stemborer pests (Figure above). It is based on in-depth understanding of chemical ecology, agrobiodiversity, plant-plant and insect-plant interactions, and involves intercropping a cereal crop with a repellent intercrop such as desmodium (push), with an attractive trap plant such as Napier grass (pull) planted as a border crop around this intercrop. Gravid stemborer females are repelled from the main crop and are simultaneously attracted to the trap crop. Napier grass produces significantly higher levels of attractive volatile compounds (green leaf volatiles), cues used by gravid stemborer females to locate host plants, than maize or sorghum. There is also an increase of approximately 100-fold in the total amounts of these compounds produced in the first hour of nightfall by Napier grass (scotophase), the period at which stemborer moths seek host plants for oviposition, causing the differential oviposition preference. However, many of the stemborer larvae, about 80%, do not survive as Napier grass tissues produce sticky sap in response to feeding by the larvae which traps them causing their mortality. Legumes in the Desmodium genus (silverleaf, D. uncinatum and greenleaf, D. intortum), on the other hand produce repellent volatile chemicals that push away the stemborer moths. These include (E)-ß-ocimene and (E)-4,8-dimethyl-1,3,7-nonatriene, semiochemicals produced during damage to plants by herbivorous insects and are responsible for the repellence of desmodium to stemborers.
Read more: How Push-Pull Works