Maize pest meets its match in desmodium and napier grass

A drive from Nakuru to Kericho leaves someone with farming interests with mixed feelings.

Along the road at some areas it is evident that people would have a bumper maize harvest while at others, the crops withered due to poor rains.

Our destination, however, is Kedowa, some 40km to Kericho, where a group of 200 farmers are practising a new technology to improve their maize yields.

On this day, farmer Richard Soi hosts the group. His two-acre maize farm looks like it experienced different weather patterns.

Part of his farm has yellowing plants, an evidence of attack from some pest or disease.

On the other part, which is a smaller section, the maize crop looks healthy with a dark green foliage.

The healthy crop is surrounded by napier grass (Pennisetum purpureum) and intercropped with desmodium (Desmodium uncinatum).

The two are used to control stem borer, a destructive pest that affects the maize crop.

The technology known as push-pull is an innovation from International Centre of Insect Physiology and Ecology (Icipe) and Kenya Agricultural and Livestock Research Organisation (Kalro), among other partners. At larvae stage, stem borer bores hole into the maize stem and eats from inside.

It also destroys leaves and eats the grains.

About 30 per cent of maize grown in the country is affected by the pest, which is prevalent in Rift Valley and parts of Central Kenya like Murang’a.

From the small parcel of his land on which he has intercropped maize with desmodium, Soi expects to harvest six 90kg bags of maize, thanks to ‘push-pull’ method.

Besides, he will harvest napier grass and desmodium as feeds for his three dairy cows.

His farm is among 11 others where the technology is being implemented in Kericho County under the Grains Integrated Pest Management (IPM) for East Africa project by Icipe.

Prof Tedele Tefera, the project coordinator, explains that desmodium produces an odour which repels stem borer moths from the maize crop.

On the other hand, napier grass has a scent that is attractive to the moth.

IMPROVE FOOD SECURITY

“The moth, therefore, lays eggs on napier grass. However, when the eggs hatch and the small larvae bore into napier grass stems, the plant produces a glue-like sticky substance which traps them to death. This way, minimal stem borer larvae survive keeping the maize free of the pest.”

Further, the ground cover of desmodium curbs striga weed. According to Prof Tefera, desmodium produces chemicals which trigger germination of striga.

When this happens when maize is off season, the striga dies because it has to attach to maize, sorghum or millet roots for survival.

“Besides, being a legume, desmodium fixes nitrogen in the soil enriching it and farmers use it as animal feeds,” he says, noting that they are doing further research to find out if farmers can intercrop maize and beans alongside desmodium.

Entrepreneurial farmers can further produce desmodium seeds for sale as this business has barely been explored.

A kilogramme of the seeds, according to Icipe, fetch between Sh600-Sh800.

Kericho County Director of Agriculture Johnstone Rono said climate change has negatively affected agriculture, in particular maize farming with the crop currently having so many enemies, including stem borer and armyworms.

Therefore, solutions like the push-pull method, which are easier to implement are timely.

According to Icipe, stem borer affects at least 20 per cent of maize in Kericho, Nakuru and Bomet.

Besides training farmers on Good Agricultural Practices when farming maize, Patrick Kigo, Icipe’s IPM Field Research Assistant, says the project is helping improve food security.