Saving Africa’s maize and cowpea from the violet vampire

Agricultural researchers in sub-Saharan Africa are making progress towards ridding the region of the deadly parasitic weed—Striga that infests cereals such as maize and cowpea farms—by developing sustainable, multi-pronged management options that smallholder farmers could effectively and profitably deploy in their farms.

Striga is a crop parasite that is considered to be one of the biggest constraints to agriculture in sub-Saharan Africa. Also known as the violet vampire because of the beautiful violet flowers it produces, the Strigaweed mostly affects cereals such as maize and legumes such as cowpea grown in the region. Farmers regularly lose 40 to 100 percent of their crops, with total losses amounting to about US$1.2 billion every year and affecting the livelihoods of more than 25 million smallholder farmers.

Like a vampire, the pest sucks and drains its host of water and vital nutrients to the point that the infested plant withers and dies. What makes Striga much more deadly is that it does most of its damage underground, even before emerging and being visible to farmers above the soil surface. By the time the weed and its tell-tale violet flowers appear, it's already too late― there is not much that farmers can do to save their crop.

Striga produces hundreds of thousands of seeds per plant, leading to massive build-up in the soil that can remain viable for many years. To control this parasitic weed, farmers commonly use cultural methods and post-emergence herbicides, which are largely ineffective in protecting the crop as most of the damage has already been done below the ground/underground. Although this may provide some relief against Striga, the herbicides are nonselective, and are too costly and unavailable for most farmers to use in the long run.

In June 2011, a private public partnership coordinated by the International Institute of Tropical Agriculture (IITA), launched a collaborative effort known as the Integrated Striga Management in Africa (ISMA) project, to develop a package of Striga control options for smallholder farmers in Kenya and Nigeria. The project is funded by the Bill & Melinda Gates Foundation and is being implemented in partnership with the International Maize and Wheat Improvement Center (CIMMYT), International Centre of Insect Physiology and Ecology (icipe), African Agricultural Technology Foundation (AATF), BASF Crop Protection, and national agricultural research and extension services and private sector players in Kenya and Nigeria. ISMA's main goal is to promote proven Strigamanagement technologies that can be deployed and work in smallholder farming conditions.

The four-year project focuses on improving access to Strigacontrol solutions that include using Striga-resistant maize and cowpea varieties, deploying a “push-pull' technology that involves intercropping cereals with specific Striga-suppressing forage legumes, using maize varieties resistant to Imazapyr—an herbicide used in coating the maize seeds (StrigAway®) and which kills the Striga seed as it germinates and before it can cause any damage— encouraging maize-legume intercropping and crop rotation; and adopting Striga biocontrol technologies. A significant component of the ISMA project is the identification of best-bet combinations of the available Strigacontrol options for specific socio-ecological targeting.

“The suite of integrated Striga control interventions being promoted by ISMA will generate an estimated US$8.6 million worth of maize and cowpea grain annually in project sites in Kenya and Nigeria,” Mel Oluoch, ISMA project manager said.

“We are also optimistic that the interventions will lead to 50 percent more yields in maize and more than double the cowpea harvest in Striga-infested areas. About 250,000 farmers will directly benefit from the project,” he added.

One year on, the initial outputs of the ISMA project have been encouraging. In Kenya, almost 6,000 farmers in the western region now have access to new Striga and the Imazapyr-resistant (IR) variety and maize-legume intercrop Striga control technologies. Partner seed companies have produced 66 tons of seeds that use Imazapyr herbicide-resistant maize coating technology, with over 35 tons disseminated to more than 23,000 smallholder farmers through participating agro-dealer networks. To enhance IR seed production and distribution in Kenya, the project supported the Kenya Seed Company with a dedicated seed 'treater' early this year. IR-maize coating technology, combined with the use of Striga-resistant maize varieties, reduce the emergence of the parasitic weed by up to 60 percent. To complement the approaches, over 75 agro-dealers in Kenya were trained on the IR maize seed technology to enhance its dissemination as they are the first point of contact with farmers purchasing seed.

As part of the push-pull Striga management technology being espoused by the project, community seed producers and partner seed companies have produced and disseminated some 2.1 tons of Desmodiumseed to farmers. Desmodium is a forage legume that, when deployed in maize or cowpea farms as intercrop, can significantly reduce the incidence of Striga by up to 100 percent within two years. The project has also trained more than 8,000 farmers on the push-pull technology, with 6,800 of them using it in their farms. The project is also working with the Ministry of Agriculture in Kenya to mainstream the use of Strigacontrol technologies into the Ministry's extension program so as to reach more farmers.

In Nigeria, the project worked with 100 communities in Striga hotspots in Kano and Bauchi States and established 500 on-farm demonstrations of improved cowpea, maize, and soybean varieties along with Striga management technologies.

About 500 tons of certified seed of Striga-resistant maize varieties were produced by participating seed companies and community-based seed producers and distributed to project beneficiaries. These open-pollinated varieties and hybrids are proven to produce 30 to 75 percent more grain, reduce Striga damage by 20 to 50 percent, and lessen Striga incidence by 22 to 88 percent compared to the commonly grown farmers' varieties and commercial hybrids. On the other hand, these partner seed companies and community seed producers have also produced some 142 tons of certified seeds of Striga-resistant cowpea varieties, with almost 80 tons sold to farmers across 100 communities in the two states.

The project has trained some 3,500 farmers on group dynamics, participatory approaches, modern crop management, and Striga control practices in Northern Nigeria. In addition, the project has also disseminated Striga management technologies to about 38,000 Nigerian farmers through farmer-to-farmer knowledge transfer, on-farm demonstrations, field days, and radio.

Researchers working under the ISMA project also conducted field evaluation of the effectiveness of biocontrol technology against Striga in maize farms of Northern Nigeria. Their findings show that the biocontrol agent and resistant maize combinationreduced Striga incidence by 26 to 60 percent and also resulted in 68 percent more yield compared to farms that grew farmer-preferred varieties alone.

The successful models in the two countries will be scaled out to other sub-Saharan Africa countries with similar ecologies and where Strigais also a major concern to maize and cowpea production systems.