Farm Futures, IL
04-27-06
More Fungicide Seed Treatment Choices Available for Early Planted Beans
Farmers are planting beans earlier than in the past, but with early comes more
diseases.
Rod Swoboda
Every year, weather permitting, farmers seem to be planting corn and soybeans
earlier- especially beans. This early planting is one of the most important of
several factors that may lead a farmer to consider using seed treatments.
"Not to jinx us, but if the favorable weather holds, bean planting could start in the
April window," says Clarke McGrath, Iowa State University Extension crop
specialist. "That would make seed treatment information especially pertinent."
Probably, the most common soybean disease problems in Iowa are seedling
damping off and seed rot caused by several fungi. Early season damping off and
root rots are often followed by premature death, which in many instances may be
attributed to fungal infections earlier in the season.
Sometimes large areas of a field or even entire fields need to be replanted due to
early season fungal problems. This is especially true when cool, wet weather
early in the growing season creates favorable conditions for infection by certain
soilborne pathogens that attack developing soybean plants.
Beware of cool, wet weather early
"Several pathogens are involved in damping off seedling diseases, with our most
common being species of Fusarium, Phytophthora, Pythium, and Rhizoctonia,"
he says. "All four are capable of killing soybean seedlings or at least causing
sufficient damage so that the plant cannot achieve its full yield potential."
Seed treatment fungicides are available in a variety of formulations. Some
products are labeled for commercial use in slurry- and mist-type seed treaters.
"This is the most common type many local seed dealers apply," says McGrath. "I
tend to favor these, as the coverage is generally good, seed is handled gently,
we have access to most of the top products, and we can make the decision to
treat/not treat by assessing soil and weather conditions close to planting time."
Other products are labeled for on-farm application, commonly referred to as
hopper-box or planter-box treatments. "Good seed coverage is required for
maximum benefit, and there are several good products in this line as well--if you
don't mind treating your own beans," says McGrath. "Talk with your local seed or
chemical dealer for specific information on types of treatments and availability. "
Considerations to help you decide
McGrath lists some factors to help you make up your mind if you are deciding
when to use a seed treatment:
▪ The beans are being grown for seed. Wisconsin research indicates better seed
quality with parent stands being treated under stressful conditions.
▪ Planting in conditions that will delay germination, such as cool soils, dry soils.
▪ Planting moderate to poor quality seed (usually defined as less than 80%
germination). Article addressing this year's seed quality issue www.ipm.iastate.edu/ipm/icm/2006/4-3/seedquality.html.
▪ Planting beans on beans. He is hearing of more beans on beans this year.
▪ Planting into poorly drained soils.
▪ Planting no-till/min till into stressful conditions.
▪ Planting in fields with a history of soybean disease problems.
"It may take more than one of these factors to lead to problems with plant health,
as disease problems are hard to predict," he points out.
Research in southwest Iowa by McGrath and seed suppliers in the area indicate
that when conditions meet several of these criteria, the probability of getting a
yield response to using a fungicide seed treatment is good. "But we don't have
enough years of data yet in our trials to say much more than that," he adds.
A quick rundown of the various types of seed treatments and what they control is
at www.extension.agron.iastate.edu/soybean/seedfungtmt.html. "I recommend a
broad spectrum treatment if you choose to use a treatment, for protection against
the widest range of pathogens. Each brand name may not be listed, but I think
every active ingredient in the combination products should be on the list," he
says.