Maize (Zea mays L.) carrying acetolactate synthase (ALS) target-site resistance allows application of high herbicide levels, which can be localized on or near the crop seed. Seed coating was tested as a cost-effective procedure for preventing damage from parasitic Striga hermonthica (Del.) Benth. (witchweed) and S. asiatica. Imazapyr and pyrithiobac at 30 and 21 g a.i.ha-l, respectively, previously proven to be optimal seed coating rates, were used for on-farm trials in 66 farms over a period of five seasons to further evaluate the effectiveness of this technology in several heavily infested farms in Kenya and Tanzania. Seed treatment with imazapyr and pyrithiobac gave season-long striga control. Generally imazapyr had lower Striga emerged compared to pyrithiobac in Kenya. However, in Tanzania pyrithiobac rates higher than 11 g a.i. ha-1 gave almost total Striga control up to 13 weeks after planting. During 2001 long rains, the striga tolerant/resistant hybrid gave highest number of emerged Striga by the 12th week after planting in low and high rainfall regimes. Herbicide seed coating increased maize grain yield from 0.75 to 2.75 ton ha-1 (average for two seasons) about a 250% increase. These results indicate that seed dressing with imazapyr and pyrithiobac offers good Striga control and results in high maize yield benefits to small- scale farmers. This coupled with pulling rare Striga escapes can reduce infestation and be used to deplete the Striga seed bank as a stopgap until genetic crop resistance becomes available.

Conservation Agriculture Program

Text in English

0410|AGRIS 0401|AL-Maize Program

INT2340

CIMMYT Staff Publications Collection