AgriNews, IL
04-29-06
IPM proponents shooting at moving targets
NAT WILLIAMS
natw@mail.com
ST. LOUIS — Soybean pest control sometimes can be like one of those shooting
galleries at the carnival: Knock down one and another pops up.
That is one prickly problem facing researchers who are trying to create effective
means of dealing with yield and quality robbers in Midwestern soybean fields,
especially while attempting to reduce their “ammunition.”
Craig Grau, a plant pathologist at the University of Wisconsin, discussed the
problem at the Integrated Pest Management Symposium.
The conference, in its fifth year, brings agronomists together from around the
world to share successes, failures and ideas for environmentally friendly pest
control.
Soybean fields in Wisconsin and northern Illinois are coming under increasing
attack from dangers previously not a problem in the region, such as soybean cyst
nematode, sudden death syndrome and even the possibility of Asian rust. Grau
and others have discovered that solving one problem with resistant lines appears
to present new problems.
Researchers there have been breeding plants with resistance to both insects and
disease. And though there has been success, there also is trepidation.
“With our breeding program in Wisconsin we have combined resistance to aphids
with resistance to pathogens,” Grau said.
“We’ve found that many soybean aphid-resistant breeding lines are highly
susceptible to northern stem canker. That’s a big red flag, in my view. Attempts
to control one pathogen can result in increases in another.”
Selective breeding still is the most effective means of reducing inputs, according
to Ohio State University agronomist Anne Dorrance.
“Host resistance as a disease-management tool is the perfect IPM,” Dorrance
said. “It requires no action by the producer. He just needs to go through the seed
catalog and pick his varieties. It’s not disruptive to the environment. In many
regards, it’s the ultimate biological control.”
Disease resistance is a heritable, active response by the host that limits
pathogen and parasitic activity. Degrees of resistance range from total immunity
to a dead plant, which is totally susceptible, according to Dorrance. Types
include race-specific, race non-specific and tolerance.
“The problem with this is that pathogens adapt, so you end up with boom-andbust cycles,” Dorrance said.
One of the most active, ongoing soybean IPM programs in universities is the
development of varieties resistant to cyst nematode, the No. 1 economic enemy
of the crop. Gregory Tylka, an Iowa State University agronomist, said that the
pest is likely the most difficult to control.
“This is the Energizer bunny,” he said. “They’re in there forever. There’s no such
thing as a good year or a bad year for these things.”
The tiny, burrowing insect has a 24-day life cycle. Each female lays more than
200 eggs.
He has been working on a breeding program that combines SCN resistance with
resistance to brown stem rot and soybean aphid.
“I see this as a continuum of single tactics in single pests, to multiple tactics for
multiple pests,” Tylka said.
Meanwhile, with Asian rust lurking as a potential major pest for Midwestern
soybean growers, USDA is continuing to improve its sentinel tracking system,
according to Scott Isard. The Pennsylvania State University aerobiologist is a
member of a research group aimed at understanding the movement of
pathogens and pests that threaten crops.
The U.S. Department of Agriculture’s Soybean Information System has been
successful in tracking rust and keeping farmers informed of its movement.
Isard said the emphasis put on keeping the disease from crippling the soybean
production of the United States led to success in the program.
“Why has it been successful? Because of the communication tools we now have
as well as the diagnostic tools,” Isard said. “Everybody was scared. That led to
unprecedented research among researchers and government agencies.”
This year the program will expand into a more general pest and information
platform, adding another pest of legumes, soybean aphids and a second crop —
dry beans.
“We’ll continue to provide growers with useful decision support for managing
soybean rust in 2006,” Isard said.