Dar es Salaam-March 25, 2013. Thousands of farmers in western Kenya are successfully battling the invasion in their farms by a deadly parasitic weed called Striga, dubbed the violet vampire because of its beautiful violet flowers. As a consequence, they are enjoying higher yields of their number one staple, maize. This is thanks to the efforts of the Integrated Striga Management in Africa (ISMA) project that has introduced a combination of sustainable multiple-pronged management options to sustainably eliminate the weed from their fields.
Striga attacks and greatly reduces the production of staple foods and commercial crops such as maize, sorghum, millet, rice, sugarcane, and cowpea. The weed attaches itself to the roots of plants and extracts its water and nutrients adversely affecting its growth. It can cause farmers up to 100% crop loss. Furthermore, a single flower of the weed can produce up to 50,000 seeds that can lie dormant in the soil for up to 20 years.
Studies have shown that this parasitic weed is the number one maize production constraint in Western Kenya with most farmers’ fields being infested.
The four-year ISMA project is demonstrating the effectiveness of using a combination of existing and new technologies developed by various national and international research organizations and private companies, to
sustainably control the beautiful but lethal Striga weed.
The technologies range from simple cultural practices such as intercropping maize with legumes, such as groundnuts, rotating maize with soybean (soybean stimulates the Striga to germinate but it later dies in the absence of a maize host to latch onto) to deploying a “push-pull’ technology that involves intercropping cereals with specific Striga-suppressing desmodium forage legume.
Other technologies include using Striga-resistant maize varieties and maize seeds coated with and resistant to Imazapyr-an BASF herbicide (StrigAway) developed by the International Maize and Wheat Improvement Center (CIMMYT) which kills the Striga seed as it germinates and before it can cause any damage. The project is also testing the effectiveness of biocontrol technologies which use a naturally occurring host-specific fungal pathogen that kills the Striga at all stages without affecting other crops.
“Striga is very difficult to control and all the various methods have their challenges. Therefore the key to sustainably manage this weed is to combine various technologies,” says Dr Fred Kanampiu, a CIMMYT agronomist leading the project activities in Kenya. “ISMA is providing farmers with options and they can choose the combination that works best for them.”
According to Dr Mel Oluoch, the project manager based at the International Institute of Tropical Agriculture (IITA) which is coordinating the project, over 6,000 farmers in the western region of Kenya now have access to the Imazapyr-resistant (IR) maize variety and maize-legume intercrop and rotation technologies.
Furthermore, Dr Oluoch says, on-farm studies have shown that Imazapyr resistant-maize and Striga-resistant maize hybrids reduce Striga emergence by more than 60% and increase maize yields by two to three times compared with the current commercial open-pollinated varieties and hybrids commonly grown by farmers.
“Partner seed companies have produced 98 tons of IR maize seed, with over 44 tons disseminated through commercial channels consisting of agro-dealer networks. Another 6.5 tons have been disseminated to at least 29,000 smallholder farmers in the Striga hot spots of western Kenya,” Dr Oluoch said.
George Martin Mitende,56, from Bonda village in Migori County is one of the farmers who donated land on his farm to the project for demonstration of the technologies. He said the project researchers requested for that part of his land that was the most affected by Striga to the project to set up a the trials in 2011.
With the application of a combination of the new technologies, Mitende now gets more maize from this parcel of land than from the rest of his farm. He says that Striga has been dramatically decreasing on this piece of land. He notes that although the piece of land is about a quarter of an acre only, he has been able to repeatedly harvest four 90-kg bags of maize for the last two growing seasons. He usually harvests only one to two bags per acre from the rest of his farm.
“My favorite Striga control technology is intercropping Desmodium with WS303. I will extend this technology to the rest of my farm,” he says.
WS303 is an IR maize variety being marketed by the Western Seed Company.
Desmodium, a legume that is also fed to livestock, is intercropped with the maize to suppress the growth of Striga as part of the push-pull Striga management technology developed by the International Centre of Insect Physiology and Ecology (icipe) and partners.
To ensure availability of Desmodium seeds, Mr Jimmy Pittchar, a Research Scientist with icipe, says the project has been working with community seed producers and partner seed companies who have produced and disseminated 3 tons of the seeds to farmers.
More than 14,000 farmers have been trained on the push-pull technology, with
6,800 of them using it on their farms. Farmers who have adopted the push-pull technology have reported almost 100% reduction in Striga infestation and up to three-fold maize grain yield increases.
“The Striga menace is expanding in the Lake Victoria basin of Western Kenya largely due to declining soil fertility and climate change, which has created a conducive environment for increased infestation. This has made the need for a sustainable solution very urgent,” says Mr Pittchar.
The Striga problem in the region is exacerbated by the new Maize Lethal Necrosis (MLN) virus disease, a combination of two virus diseases which is fast spreading in the area and has wiped out up to 100% of maize fields in Western Kenya, including many Striga technology demonstration and testing fields.
“We need to develop integrated solutions to tackle both problems. CIMMYT and the Kenya Agricultural Research Institute (KARI) are currently screening hundreds of maize inbred lines from the genebank and other sources to help identify MLN- resistant sources to be used for resistant hybrid development.
Some of these inbred lines could be used for Striga control work,” says Ms Edna Mageto, a researcher with CIMMYT.
Researchers from the Real IPM Company Ltd., a biopesticide company working in collaboration with IITA, the University of Hohenhiem, and Kenya Agricultural Research Institute (KARI) in the ISMA project are also conducting field validation of the effectiveness of biocontrol technology against Striga in maize farms of western Kenya.
The successful Striga control technology models in Kenya will be scaled out to other countries in sub-Saharan Africa with similar ecologies and where Striga is also a major concern to maize, cowpea, sorghum, and millet production systems.
ISMA is funded by the Bill & Melinda Gates Foundation and is being implemented in partnership with icipe, CIMMYT, African Agricultural Technology Foundation (AATF), BASF Crop Protection, and other national agricultural research and extension services and private sector players in Kenya and Nigeria.
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