Songa, a scientist with the Kenya Agricultural Research Institute (KARI), works with national colleagues and CIMMYT entomologist David Bergvinson on the Insect Resistant Maize for Africa (IRMA) Project. Funded by the Novartis Foundation for Sustainable Development,  the project develops improved maize that is adapted to Kenya’s main growing environments and resists destructive stem borers. *Resistance is being obtained from conventional sources and also through genetic engineering to incorporate genes from Bacillus thuringiensis,  commonly called Bt. Knowledge and technologies generated by the Kenya-based project will be offered to other countries in the region.

In this,  the third year of the project,  the entomologists are a focal point for many activities. Progress has been made in four key areas,  according to Bergvinson: yield assessment, baseline studies to characterize insect populations,  management of insect resistance,  and bioassays on conventional and Bt maize.

Getting a Handle on the Stem Borer Problem

The assessment of yield losses in Kenya’s five major maize-growing environments,  on experiment stations as well as farmers’ fields,  helps scientists identify where each borer is most problematic. CIMMYT economist Hugo De Groote heads up the on-farm trials (see: Are Researchers Giving Up on Africa?), while KARI entomologist Macharia Gethi oversees the on-station trials.

Preliminary results from the on-station trials under artificial infestation showed crop losses of 15–20%. Researchers will develop strategies for helping different groups of farmers cope with these losses. “We have two extremes,” Bergvinson observes. “We need to help poor farmers in the tropical areas,  where borers are more problematic but farmers have less access to new technologies—including income to buy them. We also need maize varieties for the more productive,  high-input areas, where farmers supply most of the maize for the urban market and use more new technologies.”

Checking on the Insect Community

The IRMA Project emphasizes controlling stem borers in ways that are environmentally friendly and sustainable. Songa,  KARI extension officers, and contact farmers are determining exactly which insects inhabit maize fields under different cropping systems in the respective agroecological zones. Their studies supply data to determine the effects, if any, of insect-resistant maize on a host of nontarget organisms, including beneficial insects that control the borers or other pests, pollinators such as bees, and useful “decomposers” such as ants and earthworms. A reference collection is also being established to classify the insects and organisms, to allow rapid identification in future studies.

Collecting and classifying insects is intensive work, says Songa, and she relies heavily on farmers, five in each of the five targeted regions, to maintain the plots and traps. Extension staff and KARI technicians trained by Songa visit the farms every week to collect the catch. Songa herself visits the on-farm sites to monitor the insect collection and talk with farmers about their maize problems and perspectives on new technologies.

“In most areas,” she says, “farmers can’t afford insecticides. Even if they can, many problems arise. Applying insecticide to each plant is an incredible amount of work: the shortage of labor is a real problem. Timing can also cause trouble. Often farmers apply insecticide too late to control the borers—so they lose both time and money. That’s why Bt maize would be a tremendous benefit to these farmers.”

The farm of Pauline Mweu in Masii, Machakos, is one of Songa’s favorite stops and illustrates the plight of many farmers. Pauline sets down a five-gallon pail of water she has retrieved from a distant river and greets Songa in a warm but weary voice. She is eager to ask about a problem she observed in her maize, which Songa diagnoses as charcoal rot.

It is her ability to help farmers with a range of problems, Songa says, that motivates them to work with her. Sometimes Songa’s assistance is as simple as reading the instructions on a seed or chemical label.

Pauline tends her half-acre virtually alone, occasionally with help from one of her six grown children. Unlike many farmers, Pauline still has a bit of harvested maize left as the new maize is coming on. She keeps it inside her house so as not to tempt her less fortunate neighbors into stealing it. The modest but crucial extra productivity she ekes out of the land is earned by long hours of weeding and care. Still, no amount of attention has deterred the stem borers, which already infest about a quarter of her crop. Many plants show signs of “deadheart,” which results in total loss of the plant.

Songa and Pauline check the traps together. The farmer had no idea that her maize plots hosted so many different, often beneficial, insects. To date, the IRMA Project has identified 65 insect families in Kilifi, in the humid coastal lowlands, and 45 in Kakamega, in the moist transitional zone in the west. Work continues in the other three zones.

Once the trapping and collecting are done, researchers will expose the beneficial organisms to Bt toxins under laboratory conditions to determine what effect, if any, the toxins may have on them. The next stage calls for experiments under open-quarantine conditions in which the impact of Bt maize on nontarget organisms will be monitored closely once again. An interesting twist to this work is that the baseline data will be compared with data from plots where conventional insecticides and Bt sprays are applied to determine their relative impacts on the insect community.

“This thorough approach to insect ecology was not done prior to the release of Bt maize in the United States and elsewhere,” Bergvinson comments. “I think we’ve learned from those experiences and have incorporated those lessons into this project.”

Managing Insect Resistance

A critical part of the long-term success of insect-resistant maize is to slow the development of borers that resist the toxin and explore other conventional lines of defense (e.g., tougher leaves). One way to achieve this result is to ensure that many susceptible borers mate with those that have acquired resistance. In industrialized countries, farmers growing Bt maize are instructed to plant 20%of their maize area to varieties that are susceptible to borers (50%in maize areas in close proximity to Bt cotton). These areas, known as refugia, provide breeding grounds for susceptible individuals and are the main constituent of most insect resistance management strategies.

Bergvinson explains that Kenyan farmers may be reluctant to plant part of their small fields to susceptible maize. If farmers perceive that planting refugia is uneconomic, they will quickly abandon it. “Now we ’re looking for alternate plant hosts within existing cropping systems that we can use as refugia. The host crops must prove susceptible to the borers, but their economic value for farmers must not be threatened.”

KARI entomologist Margaret Mulaa identifies hosts that are preferred sites for egg laying by the pests and also provide a high rate of larval survivorship—this in addition to meeting the economic criteria.By mid-2001, Mulaa was studying approximately 30 alternate hosts in 4 environmentally diverse sites. By 2002, test plots to assess alternate hosts should be established. Preliminary results indicate that sorghum may be effective in drier areas, and napier grass, a widely grown forage crop, may work well in areas with somewhat higher rainfall.

Bioassays: Bt Maize Meets Kenyan Stem Borers In early 2001, a bioassay was conducted in Kenya on Bt maize leaves imported from CIMMYT–Mexico. Leaves were fed to the main Kenyan borers: spotted stem borer (Chilo partellus), African maize stalk borer (Busseola fusca), C.orichalcocliellus , African pink borer (Sesamia calamistis), and African sugarcane borer (Eldana saccharina). The importation of the leaves followed an intensive approval process by Kenyan authorities. Leaves were used for the experiment to ensure that no seed or living maize plants could inadvertently move into the Kenyan environment. The bioassay—conducted by Songa, Gethi, and KARI technicians—showed that Bt genes cry1B, cry1Ab, and cry1Ab-1B were effective against C.partellus and C.orichalcocliellus, while cry1Ab-1B and cry1Ab proved lethal to S.calamistis and E.saccharina. None of the Bt genes, however, proved equally lethal against B.fusca, demonstrating an effectiveness of 50–60%. “These bioassays allow us to transfer the most effective gene combinations into locally adapted maize,” says David Hoisington, director of CIMMYT’s Applied Biotechnology Center. “Although we ’ve found a prospective control for C.partellus, the most destructive and widely distributed stem borer in Kenya, we must identify other genes to better target B. fusca.”   A Range of Resistance Work on conventional resistance has continued under project coordinator Stephen Mugo. Approximately 500 maize lines developed in Mexico were screened in Kiboko during the first half of 2001. The best lines will be evaluated under artificial infestation in late 2001 to further assess resistance to C.partellus and B. fusca and their adaptation to Kenyan conditions. By identifying a range of Bt and conventional resistances, breeders can “pyramid” or stack the toxins and defenses to slow the development of resistance in the borers. “The maize varieties that are developed will be recycled by farmers anywhere from two to fifteen years,” notes Bergvinson, “so their resistance needs to be as durable as we can make it. That includes incorporating conventional resistance.”   For more information: David Bergvinson (d.bergvinson@cgiar.org)

“If Women Are to Get Ahead,  We Must Make Ourselves Heard!” On school holidays,  Josephine Songa’s five-year-old daughter often accompanies her to work at the Katumani Field Station. There the youngster adamantly insists on “helping” her mother with her tasks. “She’s just like me,” Josephine says proudly. “Once she gets started on something, she puts her whole being into it until it’s completed.” While many of her equally well-trained colleagues have been lured out of Kenya, Josephine,  a KARI scientist who works in the IRMA Project, remains committed to staying the course. “I love my country and I treasure being near my family,” she says. She is similarly dedicated to improving the lives of farmers. “I enjoy the intellectual challenge,  but the real satisfaction would come from seeing farmers use our solutions and getting positive results” Josephine’s drive to help others extends especially to women. “This is particularly important in a country such as Kenya,  where the culture dictates that women yield to men,  both in farm fields and professional fields.” As recipient of the Cambridge-based International Biographical Centre’s International Woman of the Year Award in 2000-2001 for her services in pest management, Josephine aims to influence other women to fulfill their potential. “Many women in Kenya give up on their aspirations because of our culture—be it in a meeting or whatever, ” she says. “In most cases,  only the men will be talking. So if women are to get ahead, we must make ourselves heard. We will not be handed the opportunity.”

* See “Without Protection from Insects, No Field of Dreams for Kenyan Maize Producers,” CIMMYT Annual Report 1999-2000 (Mexico City, CIMMYT, 2000).

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© CIMMYT October 2001

Annual Report 00-2001