Seed & Chemical
Advancements in plant health
By Top Crop Manager
Fungicides are delivering more than just disease protection.
By Top Crop Manager
Growers have long relied on fungicides for effective disease control but increasingly,
research is showing that some fungicides will improve crop performance under
many conditions, even in the absence of significant disease pressure. They improve
overall plant health and provide a yield increase in many crops. BASF researchers
in the US have found that Headline (a strobilurin fungicide) consistently increases
yields on treated crops that exceeds the expected disease protection effect.
"We first started to see differences when we applied Headline on just
half a field," says Trevor Kraus, technical specialist with BASF in eastern
Ontario. "You could visually see the line between the halves. The colour
was different because the leaves treated with fungicide stayed green and remained
actively photosynthesizing, while leaves on untreated plants succumbed to multiple
stresses and dropped off."
It is not entirely clear why this is happening. Some of the effect is attributed
to cumulative yield loss due to minor outbreaks of a variety of plant diseases.
A field of soybeans, for example, might have three or four different diseases
at low levels within the crop in any given year. These yield nibblers, while
individually insignificant, collectively chip away at yield potential.
Dr. Gary Fellows, technical market manager with BASF in Research Triangle Park,
North Carolina, got a shock the first time he walked into a soybean field that
had been treated with Headline. "Until you start treating with fungicides,
you never realize how much disease is in a soybean field," Fellows says.
"I always thought that it was normal for soybean leaves to turn a brown
spotty colour when they start to die off. They did in the untreated check strip,
but those in plots treated with Headline remained green. When they finally started
to die off, they turned a very consistent yellow colour as they slowly cannibalized
its energy and shipped it off to other parts of the plant. There's a very different
look to them."
Fellows found similar results in corn. Historically, few farmers ever treat
corn unless a major outbreak of a disease like southern corn leaf blight occurs.
However, corn stands treated with Headline were better in almost every way.
The yields were better, the grain was bigger, the stalks were healthier and
they stood up better in the wind.
"Even when we're not finding diseases like mildew, frog eye leaf spot
or brown spot, when we go out actively scouting fields for disease, we are still
getting a yield increase from the fungicide treated side of the field,"
Kraus says. "Headline is obviously doing something to the crop that we're
not visually able to detect. It's doing something more to improve plant health
than simply controlling diseases."
Researchers are just starting to examine how overall plant health affects yield.
It is a broad area that requires a new approach. Traditionally studies are done
by specialists – pathologists study the effects of crop disease and entomologists
study insect damage. Plant health research requires a broader, multi-facetted
and multi-disciplined approach.
"We are starting to see more and more projects that delve into whole plant
health issues," says Albert Tenuta, a field crop plant pathologist in Ridgetown,
with the Ontario Ministry of Agriculture, Food and Rural Affairs. "If we
can understand what the detrimental effects on plant health are and find solutions,
then ultimately the producer will benefit. New varieties and products will be
developed that will provide healthier plants which means increased yields."
One surprising aspect BASF found in its research is that not all fungicides
have the same plant health effects. "Headline has an impact on plant growth
efficiency," Kraus says. "A neat example is a two year study comparing
Headline and a triazole fungicide in wheat. In 2004, there was a lot of disease
in the wheat. That year, both fungicides showed good yield increases compared
to the untreated. In 2005, there was minimal leaf disease in wheat and we still
got a consistent yield increase where we sprayed Headline. The same was not
true of the triazole fungicide."
One physiological change Headline supports is to reduce the levels of ethylene
in the leaf. "Ethylene is a stress hormone," explains Fellows. "If
a leaf is infected with a disease, one of the first things it does is to send
out ethylene that tells the plant 'I'm infected, cut me off'. It triggers this
response to kill off part of the plant to protect the rest of the plant. The
same thing happens in a drought. Reducing ethylene levels means that the plant
doesn't react as fast to cut the leaf off. Plants stay a little greener longer
and continue to put energy into that seed."
Headline also reduces plant respiration
Plants photosynthesize for energy during the day. They use light to store energy
in sugars and release oxygen. During the night-time, plants respire, breaking
down some of the sugar to release carbon dioxide to get energy. In a Headline
treated plant, there is actually a measurable drop in night-time respiration
and whenever it slows down there is a net gain in energy storage for the day.
"BASF has made a very significant investment in researching plant health,"
Fellows says. "We're doing a lot of research at major universities in Latin
America, Europe and North America, looking at the physiological aspects of what
Headline is doing to plants. Corn, soybeans, potatoes, sugar beets, fruit trees,
berries and vegetable plants all show signs of improved growth when treated
with Headline. It's about optimizing the condition of the plant during its life
cycle, allowing it to reach maximum yield and quality potential. We want to
know all the answers to better utilize the tools we've got and to better understand
and explain what's going on within the plant." -30-