In 2001, David Voegtlin from the
Illinois Natural History Survey established a network of suction
traps so that scientists could monitor the flights of soybean aphids
throughout any given season.
"Captures of soybean aphids in these
traps have been pretty revealing, and some trends may be starting to
develop," Steffey said. "For example, captures of flying soybean
aphids in the fall of 2002 were noticeable, while there were no
captures of flying soybean aphids in the fall of 2001."
Steffey notes that, because an outbreak
of soybean aphids occurred in 2003 and there were few soybean aphids
in 2002, the capture of aphids during the fall may provide some
insight into the potential for infestations to develop the following
"It is interesting to note that very
few aphids were captured in the suction traps during the fall of
2003," he said. "The presence or relative absence of the
multicolored Asian lady beetle, the primary predator of soybean
aphids, also may play a role in regulating populations of soybean
Steffey points out that very few of
these lady beetles were found during the fall of 2002, while there
were hordes of these lady beetles in 2003.
"It seems obvious that when soybean
aphids are scarce, then multicolored Asian lady beetles also are
scarce," Steffey said. "As a consequence, soybean aphids were able
to establish populations and begin population growth in the relative
absence of lady beetles early in 2003.
[to top of second column in
When soybean aphids
were plentiful, such as in 2003, then multicolored Asian lady
beetles also become plentiful after a lag time during the summer.
"The relatively low
numbers of soybean aphids captured in suction traps in the fall of
2003 and the presence of very large numbers of multicolored Asian
lady beetles suggest that soybean aphids may not get off to a fast
start in 2004," he said. "However, the weather conditions during the
summer of 2004 may encourage the growth of soybean aphid populations
in some areas."
populations thrive when conditions are relatively cool, while their
population growth slows when temperatures are high.
"We will be
monitoring aphid captures in the suction traps and aphid densities
in soybean fields throughout the season," Steffey said. "At the
first appearance of soybean aphids, we will let growers know when
growers, however, not to overreact at the first occurrence of
soybean aphids in soybean fields in their area.
"Their populations will bear watching,
but spraying an insecticide too early at the first appearance of
soybean aphids may cause more problems than it will solve," he said.
of Illinois news release]