Maize farmers use seeds to fight deadly striga weed

By Wandera Ojanji

You can feel Rose Akinyi Otieno's excitement as she walks other farmers through her maize farm. Initially, it is difficult to understand her excitement. Unlike many farms in Gongo, Rangwe Division, Homa Bay County, is reeling under the devastating effects of striga. Her excitement is built on a 400 square metres plot that clearly stands out: it has a very robust maize crop and no sign of striga.

It is one of the several plots the African Agricultural Technology Foundation (AATF), and other partners under the Striga Management Project, set up to demonstrate the efficacy of a striga resistant maize variety. The variety, imazapyr-resistance (IR) maize - locally known as Ua Kayongo, kills striga.

Dr Gospel Omanya, seed systems manager at AATF, explains that the IR maize variety — locally marketed as WS303 — is not resistant to the weed. It is only resistant to the coating herbicide (imazapyr that is marketed in Kenya as Strigaway) that kills striga and any other seed. The chemical diffuses into the soil and kills striga seed in the soil. Any striga that may have survived the soil attack is killed when it attaches itself to the maize and sucks the herbicide from the maize roots.

Striga is a parasite plant that survives by literally sucking nutrients out of the crops. Striga attaches itself to the roots of the host plant and survives by siphoning off minerals, assimilate and water for its own growth, causing serious damage and yield reduction to the infected crop.

It is now easy to understand the excitement of Akinyi and other farmers who visited similar plots in Gongo, during Kagan farmers’ field day in early last month.

Called witchweed

The residents of Gongo consider striga a gift from the devil. They have tried everything — from divine intervention, manual and forceful uprooting to seeking the intervention of witchdoctors — without any success. For many, it is the first time they were seeing a maize crop without Kayongo. What a relief this was to them then! Like many farming communities, growing maize is not optional. Besides evolving over the years to become the main staple food, maize is turning out to be a major cash crop.

But as the mother of six attests, efforts to grow maize in Nyanza and western Kenya have been perennially frustrated by these beautiful flowers. Unlike the highly valued roses that signify joy and happiness, that spice life and relationships, the beautiful purple flowers on farms in these regions are like wreaths on graves, for their emergence announces death of maize crop.

Courtesy of the flower, rightly called witchweed, Akinyi only got 38 bags from her 1.25 hectares last year. The average yield per acre in Rangwe ranges between 30-36 bags in fields not infested by striga and under good agronomic management, according to Kasimi Akumu, divisional agricultural officer, Rangwe.

Akinyi is somehow lucky. Her neighbour, Rhoda Akumu who did not apply any manure or fertiliser lost her entire crop to striga. According to Kasimi Akunga, the striga problem is further compounded by poor soils in the area and also low fertiliser applications.

Kasimi says most farmers, even those who apply fertiliser, do not adhere to the recommended volumes per acre: 50kg of DAP, 50kg of CAN for top dressing and 10kg of certified seed. Akinyi, for instance, applied 20kg of DAP, 40kg of CAN and used 16kg of certified seed for her three acres. Notably, Omanya stresses the fact that use of IR maize varieties should be accompanied with best field management practices to realise the potential of the weed killing technology.

Akumu is not the only one. According to statistics from the Ministry of Agriculture, 30-40 per cent of the cropland in Nyanza is reeling under the devastating effects of striga. Severely hit districts are Bondo, Siaya, Kisumu, Suba, Homa Bay and Nyando, with yield losses ranging from 50 to 100 per cent in extreme conditions.

Marketing seeds

There is no turning back for those who had experimented and even those who had seen Ua Kayongo in action for the first time during the field day. "I am planning to only plant WS303 for the coming October to December growing season," states John Ogal, who experimented with the variety last growing season for the first time. Kennedy Oure has since switched to the Ua Kayongo.

Aware that striga eradication will require the concerted efforts of the entire community, Oure has since mobilised his community to form Kagan Farmers Group to champion adoption of Ua Kayongo. The farmers have the Partnership to Control Striga in Kenya to thank for working to eradicate striga. The partnership, led by AATF, comprises of the International Maize and Wheat Improvement Centre, the Kenya Agricultural Research Institute, Ministry of Agriculture, seed companies, a network of NGOs and farmer associations in Kenya, the Weizmann Institute of Science (Israel) and BASF – a multinational producer and supplier of agro-chemicals.

Started as a pilot project in Kenya in 2005, the project has since been rolled out to other countries. So far, there are five varieties that have been commercially released in Kenya with Western Seed and Kenya Seed being the main seed producers. Tanzania released one variety in December and is looking forward to Tanseed International producing 100 tonnes for the next growing season. In Uganda, there are six varieties under national performance trials, hopefully to be released by end of the year.

Other strategies to control striga include cultural practices such as hand pulling and crop rotations, and using trap crops such as grain legumes, herbaceous legumes and improving soil fertility. The trap crops, such as desmodium, and groundnuts will trigger striga to germinate, but because they do not have root receptors, striga will die for lack of food nutrients, explains Samuel Mwita, the divisional crops officer, Rangwe.

However, due to the unique biology of striga, one of the best means of controlling striga is in the soil, not when it has emerged. "Whenever you see striga above ground, it has already caused 60 per cent damage to the crop," states Dr Fred Kanampiu, Senior Scientist, CIMMYT.

Effective control of striga is also difficult because of its inherently enormous reproductive ability and high seed longevity in the soil. Kanampiu explains that when striga flowers it sheds its seeds within the life cycle of its host.

A well-established Striga asiatica and S. hermonthica are capable of producing up to 58,000 and 200,000 seeds. On average the Striga seed bank can be increased by 340 per cent if no control measures are undertaken. Moreover, unless stimulated to germinate, seeds may remain dormant and viable in the soil for up to 20 years. Fortunately, this need not occur if the technologies discussed are applied.