Oscar Minkenberg at the University of Arizona College of Agri-
culture raised nearly 30 million wasps last year in a mass-
rearing technology. Why use a mini-wasp? Most of the chemical
sprays that kill whiteflies also kill the bumblebees that pollinate
the tomatoes in greenhouses. Growers have been searching
for ways to handle their insect problems without using pesticides.
Parasitic wasps attack whiteflies by laying their eggs on or under
the whitefly nymphs. As the wasp larvae feed, they destroy the
whiteflies and emerge as adult wasps to begin the life cycle again.
Three Commercial Growers Discuss Their Results
Piet-hein van Baar, manager at Willcox Greenhousese with 8 acres
beefsteak and cluster (cherry) tomatoes says, "The biggest problem
with chemicals is that when you spray, the chemical doesn't work
anymore after a while, because the insects build up resistance, and
the public doesn't want pesticides."
According to Jan de Kok of Bonita Nurseries, "I am surprised. We
have not had to spray chemicals at all. We didn't have a problem
even from the beginning."
Colorado Greenhouses pest management advisor Frank Stonaker
uses both Encarsia formosa and Eretmocerus on 70 acres of
beefsteak and cluster tomatoes. Stonaker is optimistic that
biocontrol will work out for Colorado Greenhouses. "We use
bumblebees to pollinate and we need pretty clean greenhouses as far
as pesticides go. Biocontrol is about 25% cheaper than using pesti-
cides. And the benefits are huge, because every time you spray
a chemical you damage a plant."

Source: Arizona Experiment Station Report
(condensed and abridged)