Posts Tagged ‘Paracoccus marginatus’


27th April 2015

The International Institute of Tropical Agriculture (IITA)
The International Institute of Tropical Agriculture (IITA) is expected to request about USD 200,000 from the UN Food and Agriculture Organisation (FAO) to contain a new destructive pest which is rapidly spreading through the coastal areas of Tanzania around Dar es Salaam and Zanzibar, attacking important food crops such as pawpaws and cassava as well as ornamental plants like hibiscus and frangipani.

The pest has been identified by scientists at the International Institute of Tropical Agriculture (IITA) as the pawpaw (commonly known as papaya) mealybug (Paracoccus marginatus), according to a press statement issued by the institute’s Tanzania office in Dar es Salaam recently.

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 George 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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