Farmers urged to consider deploying insects against maize stem borer pests


Scientists in Kenya carry out research on stem borer pests on maize plants during a field visit on farms with African journalists trained on climate change impacts. (Michel Nkurunziza)

Agricultural scientists are calling for more research and investment in the use of parasitoid species, aptly referred to as ‘natural enemies’, to control pests in sub-Saharan Africa.

Currently, stem borer pests such as Chilo partellus (the spotted stalk borer), Busseola fusca (the African Maize stalk borer) and the Sesamia calamistis (the African pink stem borer), are attacking maize farms in East Africa and causing widespread damage and reducing crop yields in the region.

Paul-Andre Calatayud, a senior research scientist at the Institute of Rearach and Development (IRD) in France, is currently conducting research in Kenya on the losses caused by stem borer pests.

Calatayud believes that between $1 billion and $2 billon worth of damage is caused by the pest every year in sub-Saharan Africa.

“In order to reduce this damage in East Africa, we need biological control where those pests are destroyed by their natural enemies (insects),” he said, adding that other factors such as land, crop and agricultural practices management would have to be improved in order to maximise the pest control potential of the parasitoid species.

A four-year research and development project, ‘The climate change impacts on ecosystem services and food security in Eastern Africa,’ is currently being conducted in Kenya, Tanzania as well as Ethiopia.

The research, which seeks to ascertain the ability of natural enemies to control pests, is coordinated by international centre of insect physiology and ecology (ICIPE) in Kenya.

The research also aims at creating a list of natural enemies as well as investigating effects of farming practices applied in stabilising maize production, including fertiliser use, varieties, cycle length and other methods in order to mitigate climate change impact on agriculture.

Preliminary results show that while chilo partellus pest is commonly found in low altitude areas and busseola fusca in high altitude areas, sesamia calamistis is found at all altitudes.

To combat the pests, scientists are observing the efficacy of various natural enemies such as cotesia flavipes and cotesia sesamiae (both types of wasp larvae) and certain types of vegetation such as napier grass.

Climate change problematic

Due to global warming (temperatures are estimated to increase by 1.3 to 2.1 degree Celsius by 2050) extreme climatic conditions such as drought and floods in Africa are likely to increase. This, in turn, will affect the diversity of the natural enemies and increase cereal crop losses.

The issue of crop losses as a direct result of climate change and pest increase has already reached crisis point in parts of Kenya.

Margaret Mwasi, 55, a farmer from Kipusi village, Taita county, in Kenya, said: “Since I have been experiencing rain decrease in this area, it is now about seven years without good harvest due to the pests that have increased to infest our maize. We finally resorted to cattle keeping to cope with hunger.”

Different farmers in the area say they are now fighting the pests using Neem tree products mixed with soap that they then sprinkle on their crops.

Situation in Rwanda

Speaking to The NewTimes, Dr Claver Ngaboyisonga, a maize researcher at the Rwanda Agriculture Board, disclosed that although African maize stalk borer (busseola fusca) is found in Rwanda, there is not yet a nationwide programme on the use of biological control (natural enemies) to combat the pest.

“We have not yet tried conducting any research on using biological control. We have been trying to use pest-resistant varieties. We use pesticides when it attacks maize at 10 per cent. The borer is not yet of economic importance,” he said.

On climate change, Ngaboyisonga explained that Rwanda has faced change in rainfall patterns, adding that the patterns influence temperatures that can increase pest attack and other diseases during certain periods.

Immaculee Mukangarambe, a farmer from Mwurire Sector in Rwamagana District, said she battles pests, especially in September after the planting season.

“We face the pest, locally known as ‘Nkongwa’, but agronomists recommend the pesticides to use. We also destroy damaged cobs and stems and uproot and burn young plants,” she said.