Used to getting a free lunch in apple and pear orchards, the obscure Mealybug Pseudococcus viburni is now on the menu
for a tiny wasp named P.mac. Benefits to growers will include reduced costs for insecticide, and everyone gains a
HortResearch’s Doug Allan explains that P.mac, or Pseudaphycus maculipennis, a 1.0-1.5mm parasitic wasp, has been
imported to target this foreign mealybug. New Zealand does have its own native mealybugs, which developed in an
environment not containing apples and pears and are not usually a problem to growers. So when the Environmental Research
Management Authority (ERMA) approved the release of P.mac in September 2000 it was after eight years of work by John
Charles and Doug Allan, checking what it would and wouldn’t do: it won’t target the wrong mealybug.
Arriving around 1922, possibly from Australia or North America, the obscure mealybug did find predators such as lacewing
waiting for it, but those don’t keep it under control.
Doug will be releasing up to 200,000 wasps in Hawke’s Bay between December 3 and 6, and the season’s total is expected
to be about 400,000. In preparation for the early December release of P.mac Doug has been rearing thousands of obscure
mealybugs on a diet of potatoes, to provide food for the little wasp so reasonable numbers can be produced for
liberation. He reports that each batch takes about four months to produce, but as the wasps become established the need
to keep nursery colonies will diminish.
Since it was first released only in February 2001, Doug Allan says no P mac have been found in the orchards yet.
However, the natural parasite populations in Europe and elsewhere suggest that a good level of control could be achieved
That’s another $7 million or more in the economy per year from increased sales. Fruit that needs less post-harvest
cleaning may store better, and lower insect counts will help growers maintain market share in a competitive environment.
- And all this from wasps so small that most people will never know they are there.