Jeffrey Gogo Climate Story
AS Zimbabwe marked its National Tree Planting day last Saturday (December 5), putting into the ground thousands of the native fruit-tree, Munzviru (Velvet wild Medlar), millions of its distant exotic eucalyptus cousins have come under severe attack from an invading force of foreign pests.
Natives of Australia, the triple invasive attackers — the bronze bug, the blue-gum chalcid and the red-gum lerp — are striking at both nascent and mature plantations, and wood-lots, at will.
This could spell disaster for Zimbabwe’s remaining 156 000 hectares of plantation forests, already struggling to keep deforestation, arson and veldt fires at bay, experts say. Forests are crucial to stabilising climates at both the micro and macro levels.
Locally, the pests have no cure (insects specialists would say they ‘have no natural predator’), and have now spread across the entire country. according to Forestry Commission entomologist, Mr Malvern Mushongahande. Their potential impact on human health is unknown.
The most fierce of the three accomplices is the red-gum lerp, discovered in Bulawayo in April 2014. Local scientists are still at pains trying to understand its characteristics, much less control its rapid growth.
And neither have measures to combat the bronze bug and the blue-gum chalcid, discovered here in the last eight years, yielded effective results.
“The pests took many of us by surprise, including scientists in SADC and in Africa. We do not know much about them,” said Mushongahande during a Sustainable Afforestation Association (SAA) field day at Nyabira recently.
The SAA is a new tobacco industry initiative targeting to cut the share of tobacco-linked deforestation–accounting for 7,5 percent of the national total–by planting, on the average, 4 000 hectares of eucalpytus per year over the next seven years.
Referred to in some quarters as the sugar pest, the red-gum lerp takes on the form of several small white lumps on the leaf, small conical wax caps housing a sap-sucking worm, said Mr Mushongahande.
“The bronze bug can be recognised when the gum tree leaves start adopting a bronze (metallic) like colour. The younger bugs appear in colour, size and shape like lice. The bronze bug is a sucking pest. To some extent, it causes defoliation,” he said.
“The blue-gum chalcid appears on the leaf like bumped-shaped galls. This pest is more common in nurseries. We suspect that in Zimbabwe the blue gum disease is being spread through seedlings. It mostly affects seedlings and coppices.”
Control Measures
Persistent pests attacks will cause the tree’s growth to stunt, and eventually, death will takeover. It can mean a lot of deaths — environment, and by extension by cause of climate change, human deaths.
Officials hope the outbreak can be contained. But they accept the battle is a tough one because the pests appear settled for the long-haul.
With two sap-sucking pests, Zimbabwe’s forests are indeed under fire. “We have a real problem on our hands,” lamented Mr Mushongahande.
“We have a combination of sap-sucking pests, the bronze bug and the red-gum lerp, and we have something which develops within the tree itself that cannot be reached with the use of chemicals.”
Partnering the UN’s Food and Agriculture Organisation, the Forestry Commission has trained small farmers from five provinces on managing the blue-gum chalcid, hoping this will build grassroots capacity for controlling the spread of the pest.
Limited tests carried out in Wedza have shown that imported natural enemies may tame the pests, but it will take time, said Mr Mazhangande, going on to claim additional systemic chemicals tests for use in nurseries targeting the blue gum chalcid “had worked.”
“We are hopeful that it can work on the red-gum lerp, too,” he said. “However, a more sustainable way of managing the pests is through biological control agents and within this project we have imported a predatory insect…a small wasp that lays its eggs into the galls. Its life cycle is around 20 days, depending on temperature.”
When the eggs hatch, they feed on the blue gum chalcid.
This means as the predatory insect builds up its population, it will also bring down the pests’ population until such a time the blue-gum chalcid will no longer an economic pest
Heads are still cracking over the red-gum lerp. “Regarding the red-gum lip, we are trying to import an identified natural enemy either from the USA, Australia or South Africa, which is already deploying the predators,” Mushongahande revealed.
Outdated Pesticides
Local scientists have failed to find an effective response to the eucalyptus pests outbreak, nearly a decade since they first entered Zimbabwe. And it is not for lack of expertise as it were for technology, funding, and perhaps, vision.
The Forestry Commission will have to start looking beyond serial Government under-funding to striking partnerships with private sector players like the Sustainable Afforestation Association that have serious interests in forestry to protect.
Part of the problem emanates from the use of outdated pesticides, says FAO spokesperson, Leonard Makombe.
He says Zimbabwe has accumulated stockpiles of obsolete pesticides that threaten human, animal and environmental health. Several SADC countries have successfully rid themselves of outdated pesticides.
FAO was now helping Zimbabwe take stock of the unneeded chemicals with the aim of sending them overseas for disposal.
Local technologies are incapacitated to handle such activities.
“Carrying out the inventory of obsolete pesticides is an important step towards the development of a comprehensive intervention framework for pesticides risk reduction,” said Makombe, in an emailed statement.
Climate Change Threat
With global trade on the increase, crop damaging pests such as fungi and moths have moved into new territories faster than other wildlife, helped by climate change, according to a 2013 report in the journal Nature Climate Change.
In the last 50 years, hundreds of pests and pathogens have shifted their ranges towards the poles by an average 3 kilometres per year.
But insects have been much quicker in their expansion, increasing their range by tens of kilometres a year, scientists say, blaming the movements on climate change.
So, how will the tripple invasive attackers affect the 15 million Munzviru species that the Forestry Commission targets to plant countrywide within the next year? It will not for the simple reason that Munzviru is not eucalyptus.
Mr Mushongahande knows that all too well. “People might ask why they (bronze bug, blue gum chalcid and red gum lerp) originate from Australia?
“Australia is the home of the eucalyptus. So the pests are simply following their food.”
In Australia, the three pests do not cause problems. There, natural predators make a meal of them. But Zimbabwe, desperate to curb runaway deforestation, cannot take anymore of the invasive alien species.
God is faithful.