How maize cobs are fighting weevils in Rift Valley area

Farmers in Rift valley area are saving upto 60 percent of their yields, thanks to a low cost innovation by one of their own that destroys weevils by only using maize cobs. Weevils, which have drill-like mouth parts, make a hole in a kernel and store their eggs inside. After hatching, the larvae feed on the kernel and emerge as adults.

The adult insects lay their eggs in another maize kernel, and the cycle repeats itself. By the time one weevil cycle is over the farmer is left with a sack of maize emptied of its nutritional value and maize seed that cannot be planted.

“Farmers realise when it’s too late that their maize is weevil infested, since at the earlier stage of infestation it is very hard to detect. However, one way to ascertain if the maize is infected is looking at the kernels, if they are full of holes, they break down when you press them between your thumb and index finger,” said Ngotho Kagia, the graduate from the College of Agriculture and Veterinary Sciences of the University of Nairobi who invented the new weevil blocker.

His method, now being used by farmers across the Rift Valley, halts the multiplication of the weevils. After removing the maize cob and shelling the maize, farmers are now pounding the maize cobs in a mortar and mixing the powder with maize kernels, which are then stored in jute sacks. The mixture of the cob powder and the fine films from the cobs reduces the weevils' activity, with the maize cob additionally containing a pungent smelling substance that suffocates the weevils without harming the maize kernels.

When the mixture is well compressed in jute sacks, the adult weevil that comes out of a maize kernel cannot find another kernel immediately. The fine film and the powder from the cob hinder its movement. The weevil finally gets tired and dies therefore reducing to almost nil the chances of any further eggs being laid.

Scientists are encouraging farmers to additionally embrace harvesting methods to further cushion them from weevil attacks during storage. A late harvest increases the chances of pest attacks. According to the scientists, maize opens the husks- ears- when it reaches maturity.

If it is raining, water enters the maize cob with the maize acquiring a yellow colour and it eventually starts rotting. Once the maize ears are open, weevils and other pests also gain easy access and start destroying the maize even before it is harvested. Maize that is left to stay on farms after it matures also becomes prone to fungal infestations. “Farmers should understand that the most serious problems always come from trying to store grains that are already infested,” said Jamleck Karanja one of the scientists said.

The success of the new indigenous method of pest control, which farmers say is achieving almost total eradication of the weevil, has even inspired applications in other crops like cowpeas, beans and sorghum, which are equally susceptible to weevil attacks. “We were grappling with the twin menace of afflatoxin and weevil attack, but we are comfortably managing the weevil and this new application has proven equally effective in our other crops like beans and cowpeas,” said Ruth Ndarwa a Rift Valley farmer.

Ngotho developed the method at a time when he was struggling to get a job after graduating. Of the many indigenious knowledge applications he is developing to save farmers from pests, the weevil blocker has been the most embraced, owing to the high cost of pesticides and the huge attachment farmers have to maize production.