The pest has been identified by scientists at the International
Institute of Tropical Agriculture (IITA) as the pawpaw mealybug
(Paracoccus marginatus), according to a press statement issued by the
institute’s Tanzania office in Dar es Salaam yesterday.
In recent years, this highly invasive pest has also been spreading and causing damage in many Asian and West African countries.
With its origin in Mexico, it was first observed on the African
continent in Ghana in 2010 from where it spread to Benin, Nigeria, Togo
and Gabon.
The discovery of the mealybug in Tanzania means that the rest of
East Africa will now likely be affected as well, the statement said.
Describing their nature, the statement said the pests are tiny, white and flat which sap the life out of the plants.
Their preferred hosts are pawpaws, but they also affect a wide
range of crops including cassava, beans, coffee, pepper, melons, guavas,
tomatoes, eggplants, cotton and jatropha.
If not controlled, it said, the pest may result in massive damage and loss of livelihoods for many farmers in the country.
The pawpaw mealybugs appear as white fluffy spots on the undersides
of leaves, branches and fruit, and are often accompanied by an
unsightly black, sticky substance coating these surfaces – a result of a
sugary excretion by the pests which attracts mould.
The affected plants don’t grow properly, and farmers are unable to
sell the often misshapen, discoloured and, in severe cases, completely
shrivelled fruits.
According to IITA entomologist Dr James Legg, one of the scientists
leading efforts to contain the pest after first noticing its damage at
his home garden, the pawpaw mealybug is currently one of the most
destructive and rapidly spreading invasive insect species.
“In Tanzania we have observed the pests along the coastal belt
around Dar es Salaam and its environs, mostly on pawpaws, cassava and
ornamental plants such as hibiscus and frangipani. But we need to carry
out a survey throughout the country to determine the full extent of
spread and the range of plants affected,” he said in recent remarks.
“Samples sent to IITA’s Biological Control Centre for Africa,
located in Cotonou, Benin, have been positively identified as the pawpaw
mealybug by the institute’s entomologist, Dr Georg Goergen,” Dr Legg
said.
“Now that we know what we are dealing with, we need to act fast.
The pest can easily spread throughout the East African region causing
major damage and threatening the food security and incomes of tens of
thousands of Tanzanian farmers,” he added.
The mealybugs are easily blown by the wind or transported by ants
from one plant to another, and are transported longer distances by
people who unknowingly carry infested plants or fruit from one part of
the country to another, or from country to country.
Efforts are under way from IITA, the Agriculture, Food Security and
Cooperatives ministry, and the UN Food and Agriculture Organisation
(FAO) to mobilise funds to use biocontrol agents to contain the pest
before it gets out of hand, the statement said.
This involves introducing natural enemies of the pest such as
parasitoids – extremely tiny insects that lay their eggs inside the
pawpaw mealybug. As the eggs hatch, tiny worm-like “larvae” emerge,
which then eat the mealybug from the inside out.
According to Elibariki Nsami from the National Biological Control
Programme of the Agriculture, Food Security and Cooperatives ministry,
using biological control is the only effective way to manage the pest
menace. Most pesticides are not effective since these mealybugs coat
themselves with a protective wax, he said.
“The biocontrol mechanisms are safe as they are very specific and
only attack the pawpaw mealybug. They are also cheap, cost-effective,
and safe for the environment,” he added.
Experts say it will also be important to set up a surveillance
system to track the spread of the pest in the country and the wider
region and to create awareness among the farmers and larger public on
how to control it.
IITA is one of the world’s leading research partners in finding solutions for hunger, malnutrition and poverty.
Its agricultural research for development (R4D) addresses the needs of the poor and vulnerable in the tropics.
It works with public and private sector partners to enhance crop
quality and productivity, reduce risk to producers and consumers and
generate wealth from agriculture.
The institute’s R4D covers biotechnology and genetic improvement,
natural resource management, plant production and plant health, and
social science and agribusiness.
For the last 45 years, IITA has focused on key tropical food crops
such as bananas and plantains, maize, cassava, soybeans, cowpeas, tree
crops and yams.
It is determined to use research in improving food security,
increasing the profitability of foods and other agricultural products,
reducing risks to producers and consumers, and helping national entities
expand agricultural growth.
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