Sunflower Bee's a Great
A hard-working native bee can sometimes top the pollination prowess of the
domesticated honey beeeven when badly outnumbered. "In our
experiments using outdoor enclosures," says
ARS entomologist Vincent J. Tepedino,
"sunflower leafcutting bees spread out evenly among sunflowers instead of
visiting just the plants nearest their nesting boxes."
Tepedino has affectionately nicknamed the bees "megapugs," short
for Megachile pugnata. They're native to southern Canada and most of
the United States except the lower Mississippi Valley and Gulf Coast.
Dark-colored and about 3/4- to 1-inch-long, the bee forages on sunflowers
and other species in the sunflower family. It uses leaf pieces and moistened
soil to make partitions between compartments, or cells, that house its young.
"Megapugs could be used wherever sunflowers are grown," Tepedino
notes. "They are charming and dutiful. Every sunflower grower should have
Tepedino used four 100-by-20-foot screened enclosures, owned by Pioneer
Hi-Bred International, Inc., at Woodland, California, for the experiment. One
kind of sunflower produced significantly larger and heavier seeds after being
pollinated by the megapugs than when pollinated by domesticated honey bees,
The test was the first using sunflower leafcutting bees to pollinate hybrid
sunflowers in field cages, says Tepedino. In earlier work, other ARS
researchers at Logan, Utahwhere Tepedino is basedscrutinized
megapug performance in open fields. There, too, the bees were better than honey
bees as outdoor pollinators of sunflowers.
In the new test, Tepedino enclosed bees within the four cages, each with
about 600 sunflower plants inside. For around 2-1/2 weeks, about 100 sunflower
bees in each of two cages performed pollination chores. Meanwhile, a few
thousand domestic honey beesover 10 times more than the
megapugsperformed the same task in two other cages.
For one type of sunflower, there was no significant difference in the size
of seeds harvested or the total seed weight per flower head. For the second
kind of sunflower included in the experiment, however, those pollinated by the
sunflower leafcutting bee produced seeds that were about 30 percent larger, on
average, than seeds on plants pollinated by honey bees. Total seed weight per
flower head was also about 30 percent greater.
Tepedino expects to have results of a follow-up study late this year or in
early 2000.By Marcia
Wood, Agricultural Research Service Information Staff.
Vincent J. Tepedino is at the
USDA-ARS Bee Biology and Systematics
Laboratory, 5310 Old Main Hill, Logan, UT 84322; phone (435) 797-2559, fax
"Sunflower Bee's a Great Pollinator!" was published in the
September 1999 issue of
Agricultural Research magazine.