What is 'push–pull' ?

‘PUSH-PULL’ TECHNOLOGY: ‘Push-pull’ is a novel approach in pest management which uses a repellent intercrop and an attractive trap plant. Insect pests are repelled from the food crop and are simultaneously attracted to a trap crop. A ‘push-pull’ strategy was developed by ICIPE and its collaborators for the control of stemborers and striga weed in resource-poor maize farming systems. This technology controls both stemborers and striga and improves soil fertility. Maize is intercropped with a legume, silverleaf desmodium (Desmodium uncinatum) and Napier grass (Pennisetum purpureum) is planted around the intercrop (diagram above). The desmodium produces volatile chemicals, such as (E)-ß-ocimene and (E)-4,8-dimethyl-1,3,7-nonatriene, which repel the stemborer moths from the maize ('push') while those released by Napier grass, such as octanal, nonanal, naphthalene, 4-allylanisole, eugenol and linalool, attract female moths ('pull') to lay eggs. Desmodium roots produce chemicals which stimulate Striga seed germination, such as 4'',5''-dihydro-5,2',4'-trihydroxy-5''-isopropenylfurano-(2'',3'';7,6)-isoflavanone, and others which inhibit their attachment to maize roots, such as 4'',5''-dihydro-2'-methoxy-5,4'-dihydroxy-5''-isopropenylfurano-(2'',3'';7,6)-isoflavanone (suicidal germination), thereby reducing Striga seed bank. The legume also improves soil fertility through nitrogen fixation.

Chemicals (isoflavones) secreted by desmodium roots inhibit attachment of striga to maize roots and cause suicidal germination of striga seed in soil

Both plants provide quality fodder for livestock. Therefore, farmers using ‘push–pull’ technology for pest control not only reap three harvests (maize, Napier grass and desmodium); they also dramatically reduce the devastating effects of the parasitic weed Striga hermonthica through the effects of desmodium.