When he realised that the foliage of some of the eucalypt trees in his home village had started yellowing and eventually withering, Alexis Nserukiye first thought there was no reason for concern.

But as days passed he realised the ‘strange’ disease was quickly spreading to new areas, destroying several trees.

The resident of Mugombwa Sector, Gisagara District was worried that this could mean the end to eucalyptus trees in an area where many residents depend on the trees for firewood and building poles.

"It all started about five or six months ago. Some tree leaves started turning yellow and eventually withered,” Nserukiye recalls

It turned out that small insects were the reason behind the withering of the trees.

"They look like lice. The only difference is that they have wings and can fly,” Nserukiye says, while demonstrating from one of the parasitic insects that he had captured.

The fact that they are winged gives them ability to move from one place to another fast and when they land on the human body they suck blood from the body, causing slight pain, according to residents.

It is believed that the lice-like insects feed on eucalypt leaves, sucking their fluids until the leaves turn yellow and later wither. The entire tree then dries up later.

"So many eucalyptus trees have been affected,” Christophe Makombe, another area resident says.

The residents say they fear a decrease in tree population might affect the ecosystem and harm the environment as well as their socio-economic life.

"We are afraid in the near future these insects might cause a significant decrease in forests thus depriving us of firewood, timber and causing significant deterioration of our environment,” Nserukiye says.

"The government should act quickly to stop the spread.”

"Flying louse”

Eucalyptus trees are the most common tree species in the country.

Eucalyptus Maidenii species are the most affected by the bugs, officials and residents say.

There are no clear statistics on the total surface of forests affected by the insects, locally known as Inda z’inturusu but officials say the disease is affecting several districts.

The districts of Gisagara (south), Bugesera, Gatsibo, Rwamagana and Ngoma (east) and part of Bumbogo Sector in Gasabo (Kigali) are the most affected regions in the country, according to the Rwanda Natural Resources Authority (RNRA).

The bugs have so far destroyed several hectares of forests, though officials say a full inventory of the damaged surface is yet to be completed.

In Gisagara alone, over 15 hectares were reportedly destroyed by end of July, according to district officials.

The insects keep moving to new areas, Justin Uwizeye, a forests officer at the district told The New Times.

Adrie Mukashema, RNRA deputy director general for Forestry and Conservation, said they are monitoring the situation and are working on appropriate solutions.

She told The New Times last week that the bugs might have evolved as a result of changing weather patterns and this year’s long dry spell.

"This year, the rainy season ended earlier than expected and this could have contributed to the disease prevalence,” Mukashema explained.

"The most affected regions are those historically known to be drought prone,” she noted

She said combating and controlling the insects is difficult but added that they are hopeful that the bugs will be eliminated with the forthcoming rainy season.

"Residents should not worry because the meteorological department has forecasted enough rainfalls in the coming season,” she said.

The affected trees will be cut down and replaced with disease-resistant plants in the coming months, she said noting that nurseries are being prepared in that regard.

Mukashema advises residents to take good care of their trees "the same way they care their crops” as a way of ensuring proper growth.

 Eating down trees

Mukashema described the insects as Leptocybe Invasa, a wasp-like insect that is prevalent in many countries around the world and which causes damage to young eucalypt plantations and nurseries.

Believed to have originated from Australia, the ‘wasp’ has spread to most eucalypt-growing countries in Africa, Asia and the Pacific, Europe, North America and the Near East.  

In the region, the insects have been reported in Kenya, Uganda and Tanzania

The wasp-like pests attack the leaves and stems of young eucalypt trees and seedlings, according to experts.

Leptocybe invasa causes bump-shaped galls on the midrib, petioles and stems of young eucalypt trees, young coppice and seedlings, according to the UN Food and Agriculture Organisation (FAO).

Severely affected trees lose leaves and show gnarled appearance, loss of vigour, stunted growth, and dieback,  the organisation adds.

However, other description and observation of the insects that have ravaged eucalypt plantations also point to another type–the Redgum Lerp Psyllid.

Scientists say the tiny bug also known as jumping plant lice, sucks the eucalyptus juice from the leaves and then secretes sweet syrup called honeydew. Newly hatched psyllids form a "lerp,” or protective covering, over themselves with the honeydew. Eventually, the eucalyptus leaves turn black, then drip down before the entire tree dies.