Seed Dressing Maize with Imazapyr to Control <i>Striga hermonthica</i> in Farmers’ Fields in the Savannas of Nigeria

Use of small doses of imazapyr and pyrithiobac for seed coatings of imazapyr-resistant maize hybrids (IR-Maize) offers an effective means to control <i>Striga hermonthica</i>. Field trials were conducted in Bauchi and Kano States of Nigeria in 2014 and 2015 under heavy <i>Striga</i> infestation to evaluate the potential effectiveness of herbicide coated hybrids maize on <i>Striga</i> control in farmers&#8217; field. Results showed that herbicide coated seeds reduced number of emerged <i>Striga</i> per m² and <i>Striga</i> damage symptoms in farmers&#8217; fields in all the locations. In Kano the number of emerged <i>Striga</i> was 4.9 to 7.9 times less in herbicide treated hybrids in comparison with those of the same hybrids planted without herbicide treatment. The <i>Striga</i>-resistant open pollinated variety (OPV) (TZL COMP1 SYN) had 6.7 to 8.0 times more <i>Striga</i> than the treated hybrids. In Bauchi, the number of emerged <i>Striga</i> on the untreated IR-maize hybrids were over four-times higher on the treated IR-maize hybrids than on the untreated hybrids. The <i>Striga</i>-resistant OPV check had four-times more <i>Striga</i> than the treated IR-maize hybrids and twice more than the untreated IR-maize hybrids across the two years. However, the effects of herbicide seed coating on grain yields were not consistent because of strong seasonal effects. The result revealed that coating of imazapyr-resistant hybrid maize seeds with imazapyr was effective in reducing <i>Striga</i> infestation in farmers&#8217; fields. Although herbicide seed coating did not give consistent yield advantages of the hybrids over the untreated checks, a combination of herbicide seed treatment and genetic resistance to <i>Striga</i> would serve as an effective integrated approach that could significantly reduce the parasite seed bank from the soil and prevent production of new seeds. The IR-hybrids and the OPV checks contained <i>Striga</i> resistance/tolerant genes that protected them against drastic yield loss in the <i>Striga</i> infested fields in both Bauchi and Kano.