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Striga
weed control in maize using herbicide seed coating technology
F.K. Kanampiu, J.K. Ransom, D.K.
Friesen & J. Gressel
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.
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