•According to Thiong'o Mathenge, an agronomist in Nyahururu, herbicides reduce the cost of food production by half and triple yields of crops.
•A recent survey by the Kenya Plant Health Inspectorate Service (KEPHIS) shows the 32 key Invasive species in Kenya include 11 arthropods, 10 microorganisms, seven plants and four vertebrates.
Ian Shanzu was helping on his parents’ farm in 2017, having completed university with a degree in agricultural economics the previous year.
In April that year, several farmers in his Trans Nzoia County complained of some stubborn worms that had infested their maize crops.
The sighting was reported to extension officers who then reported to the Kenya Plant Health Inspectorate Service and Kenya Agricultural and Livestock Research Organisation (KARLO).
At the time Shanzu’s family farm was attacked, the worm had reached Busia, Bungoma, Uasin-Gishu and Nandi counties.
By end of 2017, the now confirmed Fall Army Worm infestation had destroyed 70 per cent of maize crops in the affected counties, Karlo said.
Fall Armyworm (FAW) has since become a major pest in Kenya, causing losses of about a third of the annual maize production, estimated at about one million tonnes, the Food and Agriculture Organization estimates.
The FAW is now one of the 32 invasive alien species in Kenya.
“We tried everything to eliminate the armyworms, including rubbing tobacco dust on maize, but it did not go,” says Shanzu.
In 2018, the KARLO listed five recommended pesticides to be used by farmers to curb the Armyworm menace.
“This is the only time the pests began to go away,” Shanzu says.
A recent survey by the Kenya Plant Health Inspectorate Service (KEPHIS) shows the 32 key Invasive species in Kenya include 11 arthropods, 10 microorganisms, seven plants and four vertebrates.
Without pesticides and herbicides it will be impossible to control invasive species, experts say.
“If we don’t use pesticides, we will be overrun by the invasive worms,” Shanzu says.
His sentiments underscore the importance of pesticides and herbicides in controlling invasive species across the country.
Last year, CABI scientists announced the results of the first comprehensive study on the economic impact of a range of Invasive Alien Species (IAS) on Africa’s agricultural sector, which they estimated to be USD $65.58 billion a year.
Dr Dennis Rangi, Director General, Development, CABI
“This is the same resolve, urgency and investment our governments need to channel towards managing the Invasive Alien Species problem."
CABI estimated that Kenya loses $2.5 billion every year to invasive alien species with most costs going to weeding expenses.
The research took account of yield losses of major crops including maize, tomato, cassava, mango and banana.
In response to the findings, Dr Dennis Rangi, Director General, Development, CABI, said, “An estimated USD $65.58 billion a year impact of Invasive Alien Species on Africa’s agricultural sector is a tremendous loss where over 80% of people living in rural areas rely on the crops they grow for food and income.”
Invasive species usually threaten ecosystem health by reducing biodiversity; deteriorating habitat for native species, including endangered species; fuelling wildfires; reducing or changing nutrient availability; and damaging other ecological functions.
Rangi added: “The long term effects are exacerbated by Covid-19 which continues to apply intense pressure on an already fragile agricultural sector and food supply chain. Notably, Governments across the continent put in place mitigation measures to manage the pandemic and its impact. Kenya for example proposed a USD $503 million economic stimulus package in 2020 to cushion its citizens.
“This is the same resolve, urgency and investment our governments need to channel towards managing the Invasive Alien Species problem.
Image: FILE
Pesticides are one of several management tools that stop the spread of invasive species when no other solution is available or economically feasible.
The other methods of invasive plant control are mechanical and biological, but are considered less effective.
Desert locusts are another destructive invasive species.
Kenya experienced the worst infestation in 2020 and 2021 with the country resulting to use Chlorpyrifos, teflubenzuron, or deltamethrin to control them.
By October 2020, the swarms had flattened about 175,000 hectares of crop and pastureland upsetting the livelihoods of nearly 164,000 households, according to the Ministry of Agriculture.
However, there was a debate in Kenya about the use of pesticides.
“If you drink one litre, it’s not safe. But the amount of chemicals sprayed is ultra-low volume. That means one litre per hectare is very little. In 24 hours, everything evaporates,” explained Mehari Tesfayohannes Ghebre, Information and Forecasting Officer for the Desert Locust Control Organization in East Africa.
The FAO said in 2020, the locust infestation affected the food supply and livelihoods of some 2.5 million people, a figure that could have grown higher without the use of pesticides.
“Some people told us about harvesting them, but how do you harvest millions of flies that land on your shamba at night,” says William Nzau, a farmer in Makueni.
Some of the chemicals used to control the invasive species are targeted for a ban by activists keen on promoting organic farming in Kenya.
It is also part of the European Union’s plan to force countries exporting foods to Europe to stop the use of pesticides.
Chemical weed control is the most effective method to suppress weeds in order to get healthy and vigorous crop stand.”Emily Chepkoech, an agronomist from Egerton University
Okisegere Ojepat, the Chief Executive Officer of the Fresh Produce Consortium of Kenya (FPC Kenya), recently told journalists this is impossible for a country facing so many invasive plants and pests.
“[The EU] is saying ‘close that door’ without showing our people where the exit door is, while they should be able to offer solutions and alternatives that work equivalently,” he concluded.
FPC advocates for a conducive national and international business environment, policies, tariffs and trade agreements on behalf of its members.
Africa is also facing an increase in invasive weeds, some of which have their origin in South America, North America, and Asia.
Agricultural experts reckon that in sub-Saharan Africa, weeds reduce crop yields by 30 per cent to 40 per cent on average and in some cases, they can completely wipe out a crop.
CABI estimates that 50 per cent to 70 per cent of the labour in crop production in Africa and the use of herbicides is extremely low.
“Parthenium (Parthenium hysterophorus), for instance, is an invasive plant that besides causing up to 90 per cent of crop losses in agriculture, is poisonous to livestock and causes severe asthma and dermatitis in people,” said CABI in its Action on Invasive Report 2017.
It noted these weeds are best controlled through herbicides, some of which are also targeted for a ban.
Last year, Emily Chepkoech, an agronomist from Egerton University researched herbicides use in sorghum farming in Kenya.
"Sorghum is often infested by grass and broadleaved weeds known to account for 33 per cent loss of potential production and 30-45 per cent loss of plant nutrients from the soil,” she said in her study.
“Chemical weed control is the most effective method to suppress weeds in order to get healthy and vigorous crop stand.”
According to Thiong'o Mathenge, an agronomist in Nyahururu, herbicides reduce the cost of food production by half and triple yields of crops.
“The use of herbicides helps conserve the structure and composition of the soil which would have otherwise been damaged through ploughing as this would have left the field rough and cloddy,” he said.
According to the Agrochemicals Association of Kenya, there are more than 50 registered brands of herbicides that have all been assessed by the Pest Control Products Board (PCPB) and found safe.
Mathenge says all that is needed is the judicious application of these herbicides, not a ban.