Evaluation of Herbicide-Resistant Maize Hybrids for the Control of Striga Hermonthica in the Guinea Savannas of Northern Nigeria.

Striga hermonthica is a widespread parasitic weed species that can cause considerable yield loss in susceptible maize cultivars in West and Central Africa. Most of the control measures do not provide complete protection from damage. A unique approach for controlling Striga has been developed which combines seeding coating with an acetolactate synthase-inhibiting herbicide of maize hybrids (IR) that are resistant to the herbicides. Field trials were conducted in northern Nigeria to determine the performance under natural Striga infestation of 4 imazapyr treated IR maize hybrids that possess genetic resistance to Striga. These were compared with 4 non-IR maize hybrids. The treatments were arranged in two set of trials that were laid out adjacent to each other. In the first set, the hybrids were treated with the  herbicide imazapyr. In the second set, the hybrids were not treated with the herbicide.  When treated with the herbicide, none of the non-IR hybrids germinated. At 12 weeks after planting maize (WAP), Striga emergence ranged from 16-33 plants per plot for hybrids that were treated. Differences among the treated hybrids were not significant. Three hybrids produced superior yields that were statistically similar.. When untreated, the IR hybrids recorded lower number of emerged Striga (19-39 plants/plot) than the non-IR hybrids (138-172 plants per plot). Grain yield of the untreated IR hybrids ranged from 2510 kg/ha for IR-hybrid 2  to 3506 kg/ha for IR hybrid 1; grain yield of the non-IR hybrids ranged from 1652 kg/ha for the most susceptible hybrid 8338-1 to 3098 kg/ha for OBA 98.  Number of emerged Striga and grain yields of the IR hybrids did not differ between treated and untreated controls. This is probably due to the fact these hybrids were Striga- resistant and may not have to be treated with the herbicide