March 2003. Heavy infestations of mealybugs on papaya trees were reported from Palau, which was a new species. Infestations were so large that they were being washed off the fruits of papya with hose pipes. Two weeks later the trees were still looking fine, so the treatment is being recommended! A request for the identification of the mealybug was made.

Guam has recently experienced a new introduction of a devastating mealybug, the Papaya mealybug (Paracoccus marginatus), which originated from Mexico or the Caribbean area. It would seem that Palau has the same pest. USDA-APHIS has helped Guam with biocontgrol introductions that appear to be established and gradually suppressing the pest. If it is the papaya mealybug, it is devastating on papaya, and about a dozen other hosts. However, there are other mealybugs in the region that resemble papaya mealybug, but are not quite as serious.

An article in Pacnews summarises activities to control the mealybug in Guam.

06 AUGUST 2003 HAGATNA (Pacnews) – A year ago Guam’s papaya crops were being razed by an imported killer three millimetres long – the papaya mealybug.

Fortunately, however, scientists have come to the rescue and Guam’s papaya crops are now growing their way back to health.

In June 2002, Rangaswamy Muniappan of the University of Guam’s Agricultural Experiment Station, with the help of biological control specialists from the US Department of Agriculture, began releasing three species of microscopic, stingless wasps imported from Puerto Rico to combat the destructive papaya mealybugs.

Muniappan says the parasitic wasp seeks out a mealybug and deposits an egg inside of it. The egg then grows into a larva, and essentially eats the mealybug from the inside out, thereby killing it, he said.

“It’s been very, very successful,” said USDA biological control specialist Dale Meyerdirk, noting that at sites they’ve been monitoring for the last year, papaya mealybug populations have dropped by more than 95 percent.

The papaya mealybug originated in Mexico, and at some point jumped to islands in the Caribbean. When those islands’ papaya crops were wiped out, scientists went to Mexico to find the natural enemy of the pests.

Scientists found the parasites that kill the papaya mealybugs, and after sending them to a facility in Delaware for research, they introduced them to the Caribbean islands, and later to the US mainland, which the bug had also infested. Those programmes proved successful, Mr Meyerdirk said. So when the papaya-killing bug found its way to Guam, probably by hitchhiking on some imported fruits, the obvious solution was to import the parasites as well.

The papaya mealybug has spread from Guam to Palau where a similar biological control programme has been established. Mr Muniappan said the bug had not yet been reported on Hawaii or other Pacific islands.

The parasites shouldn’t present a problem to the island because their population decreases as the mealybug’s population decreases…PNS (ENDS)