Parasitoids, an imported biological control that is used to kill pests, will arrive in Rwanda by end of this week, The New Times has learnt.

The parasitoids (kind of insects) are purposely being imported to wipe out pests known as ‘mealybugs,’ that have been attacking mango trees

Mealybugs are sucking insects, soft bodied, oval shape and cottony in appearance.

They are found on leaves, stems, roots and fruits which are covered with whitish powder and can go from one tree to another.

The Mango Mealybug (MMB) attacks over 100 plant hosts but mangoes are more prone to it. It also attacks citrus, guava, bananas and paw paws.

Parasitoids, to be used in pest control, are small insects that look like wasps and kill the pests they feed on.

The "mealybugs” were first reported in the East African region in 2019 where three countries namely Rwanda, Uganda and Burundi were affected, according to Food and Agriculture Organisation (FAO).

Charles Bucagu, the Deputy Director General in charge of Agriculture Development at Rwanda Agriculture and Animal Resources Development Board (RAB), told The New Times that the mango yield could decrease by over 80 per cent if the pests are not controlled.

"Using parasitoids and other approaches could avoid further losses which mango farmers are incurring,” he said.

Experts have said that parasitoids pose no threat to humans, animal or environment.

FAO has already kicked off a biological pest control programme to manage the mango mealybug in Burundi and Uganda, and it is partnering to release biological control agents of the mango mealybug in Rwanda.

RAB commences pest invasion

Bucagu said that a campaign to curb the invasion of mango mealybugs has kicked off in many districts where mango trees have been affected.

The districts include Gatsibo, Nyagatare, Kayonza Rwamagana, Ngoma, districts of Kigali City, Bugesera, Kirehe, Kamonyi, Ruhango, Nyanza , Huye, Karongi, Nyamasheke, Rusizi among others.

Mango farmers, grass-root leaders, sector agronomists, agriculture facilitators and mentors were trained on mango mealybugs control, he said.

They were trained on how to control mango mealybugs, how to mix mealybugs killing solutions and a better way to spray insecticides on affected mango trees among others, before the biological control approach is introduced.

Trainees have been advised to wear gloves and safety glasses to protect hands and eyes when mixing or spraying the bug-killing solution.

He further said that while spraying, a farmer should spray on every leaf to make sure that the tree is fully covered.

The other pest prevention techniques, Bucagu said, include pruning tress to remove highly infested damaged branches, removing fallen old leaves from previous season, removing weeds from field borders during cropping periods to avoid alternative host to the bugs as well as spraying the whole plant, not only where mealybugs are visible.

Farmers speak out

Farmers have said that, without intervention, they were to count total losses.

Faustin Twagirayezu, a farmer from Nzige sector of Rwamagana district, had taken a decision to cut down his mango trees after being invaded by pests.

"I was thinking of cutting down all my 300 mango trees because I was harvesting nothing after failing to control the invasion of the pests. I wanted to replace the mango trees with avocado trees, but the government is pledging to help us. We had no knowledge about how to control these pests. Now technicians have decided to train and help us,” he said.

Pascal Mushimire, another farmer from Ruhango district, said that some farmers had started to sell mango trees after realising they were no longer able to control the pests.

"We tried to use rocket pesticides, but they persisted and some opted to cut down the trees because they were no longer harvesting,” he said.

These farmers are among many others across the country, who are counting losses due to pests that have invaded mango trees.

Mango trees live well over 100 years and produce fruits till the latest stages of their life cycle.

They start to produce fruits after four years if planted from saplings.

According to agricultural experts, at the start of the bearing age, they can yield approximately as low as 10-20 fruits per tree, rising to 50-75 fruits in the subsequent years, and to about 500 fruits (100 kg) in its tenth year.

At the age of between 20 and 40 years, a tree bears between 1,000 and 3,000 fruits (200-600 kg) per year.