Striga asiatica chemical control by seed coating imazapyr resistant maize hybrids

Abstract

The parasitic weed species Striga asiatica, also known as witch weed, is one of the major constraints in maize production, in Angola.Since S. asiatica seed banks are long-lived, control strategies that affect the seeds emergence and parasitism are necessary. In this study S. asiatica control was carried out, in infested fields, with a new technology using seed coating herbicide resistant (IR/OPV) with imazapyr at 30 g ha^-1. In 2009/10 and 2010/2011 seasons autochthones (non-IR) and IR maize varieties were sowed, to assess spill-over effects on Striga emergence, maize growth and production. Compared to control (non-IR) the herbicide showed a total control of the parasitic weed with an increase of about two-fold in maize production. Nevertheless maize production varied significantly with the tested variety even in the absence of the parasitic weed. There were significant (P < 0.05) effects on Striga emergence on both year trials. Results showed that imazapyr seed dressing suppressed (P < 0.001) Striga emergence to 0.0 plant m^-2, compared to about 5 plants m^-2 in untreated plots at 12 weeks after sowing. The results therefore suggest that the use of ALS inhibiting herbicides can suppress Striga emergence with an increase in maize productivity. Due to its high yielding potential the IR maize hybrids ZM521, ZM523 e ZM625 could be considered for introduction in the region.