Scientists' new trick to fight armyworms

The infestation of fall armyworms was first reported in Kenya in March 2017, the Western parts being among the first to be affected.  For five years, farmers have counted losses as they used pesticides, and homemade remedies like ash with no positive results.

Florence Ngao, a farmer in Kinanie, Machakaos County, says she went from harvesting 30 bags per acre to two bags following the infestation of fall army worms.

“It’s very demoralising and expensive. The pesticide I use costs Sh350 per 50ml that provides five pumps. In an acre, I need 20 pumps that means four times 350 which is Sh1,400. The sad part is that you can spend all that money then you see the worms again after a week or two,” she says.           

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Being a commercial farmer, Ngao says they have many customers due to the size of the maize harvested. “Nobody wants to buy small maize, so we just end up eating them and count our loses,” she says. 

Ms Ngao adds that she usually stops spraying of the pesticide three weeks to harvesting. The same fate befell another farmer Cosmas Nzioka, who decided to halt his farming due to the high maintenance.

“I started farming in 2015, the pesticide I used really affected me financially. The cost of fertilisers also skyrocketed. I am tired so I just decided to stop farming,” he says.

Before hanging his farming boots, Nzioka tried different methods of getting rid of the warms with no results.

“I used several methods, poured ashes, I even sprayed a plant called muvangi, (Mexican Maigold Weed) but still there was no change,” he says. 

But there is hope for farmers. 

Kenya Agricultural and Livestock Research Organisation (Kalro) has partnered with 14 African countries as well as scientists in South Korea to find a solution.

Kalro organised demonstrations for farmers and researchers, in Kinanie, Mavoko, Machakos County, where they used three acres of land to plant maize.

Less costly to farmers

Principal investigator for the management of fall army worms Dr Muo Kasina, says they are looking at integrating various methods of managing the fall army worms in ways that would be less costly to the farmers.

“We have three acres of land situated one kilometer apart, whereby we used different  methods of dealing with the worms. In the first one we are not using any control measure we have allowed natural infestations of fall army worm on our maize,” he says.

In the second site they applied biological control and insecticides due to high infestation, the third site they used biological control, insecticides and mating control technology.

The Field Development Director for PROVIVI Samuel Muchemi says they have developed a technology that will suppress the infestation by innovating a new mating disruption technology, known as the Pherogen dispenser.

The product comes in a package carrying 70 black sachets. The sachets contain a product that releases the scent that mimics the scent a female army worm releases when ready to mate. It is placed on a stick imitating a small erect flag then placed in the farm 20 metres apart.

“Once we put them in the field the product denies the male to find the female. If the eggs are not fertilised, then there are no new army worms. They will lay the eggs but they will not hatch due to lack of fertilisation,” says Muchemi.

Muchemi says they create a cloud inside the farm that will produce  too much scent that mimics the female scent.

”It will die naturally while still looking for the female. So the female is somewhere waiting when the male does not show up to fertilise the eggs, it will just lay them and they will die. So we minimise fertilisation and eliminating the male by letting them die a natural death.”

Muchemi says the technology also helps in reducing the insecticide used.

“We are preventing the farmer from exposing themselves to insecticides. We know the health issues that come from insecticides. We are not substituting the use of insecticides but we want them to reduce the amount  they use on the crops,“ he says.

Fear of agrovets

Muchemi says if the farmers use the technology they will only use insecticides twice or once before harvesting.

The mating disruption technique is active for 90 days in the farm, then the farmer will collect the sachet and dispose them. However, they are working on biodegradable ones.

Muchemi recommends farmers to use 20 cachets per hectare that is eight per acre, placed 20 metres apart. ”For easy calculation just make 20 large steps then place the dispenser.”

He adds that the dispensers will be readily available in the market from next year, focusing on bio degradable ones. The cost will range between 20-30 dollars (Sh3,450) per hectare.

However, Muchemi says they will focus on selling in packs, to improve efficiency.

Saying that they are discouraging sending them to agrovets believing  a farmer might decide to buy one sachet that will not give results.

During the tour of the three acres, Dr Muo Kasina encouraged farmers to embrace the new technology.

“If all the farmers buy the product then the whole area will have the scent and confuse the male in large quantity, but if this farmer embraces it then the next one does not the results will be there but not as effective,” he says.  

They also advised farmers to place the dispensers immediately they start planting.

Dr Kasina also discouraged farmers on not using the same pesticides for all their crops, and encouraged scouting g before spraying.

“Some farmers use pesticides not registered for maize and that is killing their crops. Also soil testing is very important because the soil maybe too acidic,” he says.