During the
past eight years, CIMMYT, in collaboration with the Weizmann Institute
of Science (Israel), has developed a unique approach for Striga
control in maize. It combines low-dose of a systemic acetolactate
synthase (ALS)-inhibiting herbicide seed coating applied to
imidazolinone-resistant (IR) maize seed that leaves a field virtually
clear of emerging Striga flower stalks
season-long. This maize allows application of high localized
herbicide levels on or near the crop seed, but at one-tenth the rate
that would be used as a spray application. On-station and on-farm
studies over several seasons in Eastern and Southern Africa
demonstrate that 30 - 45 g/ha imazapyr (or some other ALS inhibiting
herbicides) are optimal for seed coating for effective Striga
control in various environments. Low-dose herbicide seed dressing on
IR-maize also controls Striga without impacting sensitive
intercrops when they are planted 15 cm or more from maize hills. This
allows small-scale farmers to continue intercropping while using maize
seed treated to control Striga.
This technology
increases yields in Striga-infested
fields greater than three-fold at a cost of less than US $4 per
hectare. The added cost of this 1 ton/ha added yield is equivalent to
about 25-50 kg/ha maize yield, depending on market prices, suggesting
potential benefit:cost ratios >25:1. This technology, coupled
with pulling rare Striga escapes (some of which could be
resistant to the herbicide) can deplete the Striga seedbank,
reduce infestation of susceptible rotation crops, delay the evolution
of resistant populations, and can be used as a stop gap until genetic
crop resistance becomes available. CIMMYT
initiated a breeding program originally in Harare and later in Kenya
to incorporate adaptation of IR maize to the local environment.
This has focused on improving IR
maize germplasm for resistance to turcicum blight and leaf rust
diseases, reducing the proportion of Pioneer hybrid germplasm to less
than 12.5%, increasing seed stocks. High-yielding
and disease-resistant IR-maize inbred lines, hybrids, and open
pollinated varieties adapted to Striga-infested agro-ecologies
in sub-Saharan Africa will soon be available from CIMMYT. Our
goal is to deliver this product to farmers
in all major agro-ecologies in sub-Saharan Africa where Striga
is endemic. To achieve this goal, CIMMYT is collaborating with BASF
and with seed producers to commercialize the technology and make
seed-treated maize available to farmers.