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Headache for SA farmers as another exotic whitefly establishes itself in South Africa

Colonies of the immature Pomegranate whitefly attached to leaves by suction. Photo credit: Stellenbosch University/Anton Jordaan

The exotic Pomegranate or Ash whitefly, which can severely damage garden shrubs, apple and pear trees, olive trees, citrus and pomegranate trees, was noticed recently for the first time in South Africa by Professor Jan Giliomee, a research associate at the Department of Botany and Zoology at Stellenbosch University.  It was positively identified by Mr Ian Millar, a taxonomist of the National Insect Collection in Pretoria.

The discovery of the Pomegranate whitefly (Siphoninus phillyreae) is a further headache for South African fruit farmers and gardeners. Recently Prof Giliomee’s discovery of the exotic Woolly whitefly (Aleurothixus floccosus), which attacks citrus, also made the headlines.

Contrary to what their name suggests, these insects are not flies but are rather more closely related to scale insects and aphids. The adults look like tiny moths and fly around rapidly while at the younger stages they are suctioned onto the underside of leaves.

According to Prof Giliomee, these whiteflies have the potential to become very troublesome and to do a great deal of damage.

When they arrived in California in 1988, the whiteflies affected many shrubs and trees so badly that the plants lost all their leaves and the harvest of fruit trees was reduced.

“Young pear trees even died as a result of repeated exfoliation,” Prof Giliomee says. “In cities and towns, the sticky honeydew that is secreted during the sap-sucking early stages, landed on cars and on people and was even carried into houses by the wind to make carpets and furniture sticky too.

“It was intolerable and the pest was only brought under control in California when parasites were imported,” he said.

The Pomegranate whitefly originates in countries around the Mediterranean Sea like Spain, Italy, Israel and Egypt where, apart from garden shrubs, it attacks a wide range of fruit trees. It later spread to India, Iran and New Zealand.

A great number of pomegranate cuttings have been imported into South Africa from Israel and India in the past few years. Prof Giliomee surmises that the new whitefly entered the country with plant material that was brought in illegally and did not go through the quarantine process required by law.

Prof Giliomee says he saw the insect here for the first time on a wild olive tree in the garden of his beach house at Vermont on the Overberg coast. A month later he received heavily infested pomegranate leaves from a farmer at Halfmanshof near Porterville, who suspected that it was the Woolly whitefly. Mr Millar then established that they were, however, also examples of the new arrival.

“The fact that the appearance of these whiteflies is already so widespread indicates that they have been in the country for some time and can therefore not be eradicated,” he stated.

“The question is now whether the numbers are going to remain relatively low or whether the situation in California is going to repeat itself here,” Prof Giliomee said. “It must now be established whether wasps that prey on the pest are present here and, if not, they must be imported urgently.”

No remedies have yet been tested for combating the whitefly.

More information:

Prof Jan Giliomee
Research fellow: Department of Botany and Zoology
Stellenbosch University
jhg@sun.ac.za

http://www.sun.ac.za/news/NewsItem_Afr.asp?Lang=1&ItemID=15410

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